Neem Extract

Neem Extract

Credit: Infonet-Biovision

Neem leaf and unripe fruits (Azadirachta indica)
(c) A.A. Seif

Scientific name: Azadirachta indica

Neem can be used against the following pests African armyworm, African bollwom,Aphids, Banana weevil, Cabbage looper, Cabbage moth, Cabbage webworm, Coconut mite, Cutworms, Diamondback moth, Giant looper.

1. General Information on Neem in Pest Control

neem tree
Neem trees
(c) A.M.Varela

The neem tree has over 100 compounds with pesticidal properties. The best known is azadirachtin. This substance is found in all parts of the tree, but it is much more concentrated in the fruit, especially in the seeds. 

Neem is unique among plants with pesticidal properties since it has so many different effects on pests. It acts as a broad-spectrum repellent, insect growth regulator (it causes deformities in the insects’ offspring) and insect poison. It discourages feeding by making plants unpalatable to insects or suppresses the insect’s appetite (anti-feedant effect); if they still attack, it inhibits their ability to moult and lay eggs. Unlike most botanical insecticides, neem also has a somewhat “systemic” effect. This means that plants can take up neem extracts through their roots and leaves, spreading the material throughout the plant tissues. For this reason neem can help control pests like leafminers, which feed within leaves and are normally not affected by sprays that only cover the outer parts of the plant.

Farmers and scientists have also observed a certain preventive effect of neem oil or seed extract against plant diseases such as mildews and rusts. 

Neem products are effective against a wide range of pests; about 400 species of crop pests are known to be affected by neem extracts. In spite of its broad-spectrum action, neem products generally, would not harm natural enemies (like wasps, ladybird beetles, spiders, etc.). This is explained by the special mode of action of neem compounds, and by the feeding behaviour of natural enemies as well as the relatively low contact effect of neem products. The degree of effects on natural enemies is largely dependent on the type of formulation, and time, frequency and methods of applications. 

Adults of predatory insects are apparently not affected by dosages of neem products recommended for effective pest control. However, their activity, fecundity and longevity may be negatively affected with high dosages. Hoverflies are one of the most sensitive groups to neem applications. Parasitoids are in general less sensitive to neem products than predators. However, especially in very small species of parasitic wasps, treatment of the developmental stages of the host (for instance eggs or puparia of whiteflies) may have negative effects on the emergence rate, walking ability, searching ability, longevity and fecundity of the natural enemy.

In general, neem products based on neem oil or with high oil content have more or stronger side effects on non-target organisms than oil-free preparations. Thus, their application should be avoided or restricted on crops where natural enemies play an important role in pest control.

Some neem products, especially the ones with high oil content, are phytotoxic to some plants, this means plants may be burned when neem extract is used at a high dosage. Therefore, the extracts should be tested on few plants before going into full scale spraying. 

Neem based pesticides are suitable for organic farming and for use in developing countries because leaf or seed extracts can easily be prepared without the use of expensive and complicated equipment. However, neem extracts are rapidly ‘destroyed’ when exposed to sunlight (UV, ultra-violet rays), which means they will loose their efficacy. For this reason, commercial products usually contain a sunscreen, which protects the extract from sunlight, allowing a longer exposition to sunlight. 

The effect of neem as a pesticide depends on the concentration of the active principles, on the formulation, on the pest type and on the crop.

Neem pesticides can be prepared from the leaves or from the seeds. The leaves or seeds are crushed and steeped in water, alcohol, or other solvents. For some purposes, the resulting extracts can be used without further refinement. Ground neem seeds or neem kernel powder (before or after oil extraction) is used as a soil amendment, and it is effective for control of nematodes. It is also used for control of stalk borers, and to prepare water extracts, which are then sprayed onto plants.

Neem has also been used to protect stored roots as well as tubers against the potato moth. Small amounts of neem powder are said to extend the storage life of potatoes for 3 months.

Neem oil, extracted from the seed kernels, gives effective protection to stored beans, cowpeas, and other legumes. 

In recent years, there have been a number of studies conducted to investigate the particular effects of neem extracts on malaria-transmitting mosquitoes. There are indications that the most effective way to use neem is to apply seed extract to breeding sites when population numbers are low, during the dry season, in order to eradicate as many immature mosquitoes as possible and reduce the population available for breeding when conditions become more favourable. Once the rainy season commences, regular applications of seed extract should continue to prevent immature mosquitoes from emerging as adults (Gianotti et al. 2008). 

Use as an insecticide: The seeds are the primary source of insecticides. They can be used in the form of simple aqueous extracts or as a basic raw material for formulated pesticides. The leaves are also used as simple aqueous (water) extracts. 

Use as a nematicide: The neem cake, a by-product of oil extraction from the seeds, worked into the soil has shown to reduce to a considerable extent the reproduction and population density of numerous plant pathogenic nematode species. 

Use as a fungicide: One of the latest discoveries is neem’s potential application in the control of fungi that cause diseases to plants. Neem oil based emulsions have proven to be the most effective. 

Use as a molluscicide and acaricide (miticide): These pests are only controlled on to a limited extent with neem. Neem showed deterrent effects on land snails. Alcoholic extracts, in particular, have a negative effect on the reproduction of spider mites.

The susceptibility of different groups of pests to neem products is shown below.

  1. Pest-Beetle larvae, butterfly and moth caterpillars

Level of control-excellent

Recommended neem formulation-aqueous neem extracts

2. Pest-Stalk borers

Level of control-good

Recommended neem formulation-aqueous neem extracts and neem cake, neem powder

3. Pest-True bugs, plant- and leaf- hoppers grasshoppers

Level of control-good

Recommended neem formulation-neem oil, neem kernel extracts

4. Pest-Grasshoppers

Level of control-good

Recommended neem formulation– Neem oil

5. Pest-Adult beetles

Level of control-good/fair

Recommended neem formulation-aqueous neem extracts, neem cake powder, leaves, neem oil

6. Pest-Thrips, fruit flies, scale insects, mealybugs

Level of control-fair/poor

Recommended neem formulation-neem oil, aqueous neem extracts

7. Pest-Mites

Level of control-fair/poor

Recommended neem formulation-alcoholic extracts

8. Pest-Plant parasitic nematodesLevel of control

Level of control-good

Recommended neem formulation-neem cake, neem leaves

2. Standard Procedures for the Preparation and Application of Neem Extracts

  • Select healthy neem leaves that are free from diseases. 
  • When storing the plant parts for future usage, make sure that they are properly dried and are stored in an airy container (never use plastic container), away from direct sunlight and moisture. Make sure that they are free from moulds before using them.
  • Use utensils for the extract preparation that are not used for your food preparation drinking and cooking water containers. Clean all the utensils properly before and after use.
  • Do not have direct contact with the crude extract while in the process of the preparation, and during the application.
  • Make sure that you place the neem extract out of reach of children and house pets while leaving it overnight. 
  • Harvest all the mature and ripe fruits on the crop to be sprayed before neem application. 
  • Always test the plant extract formulation on a few infested plants first before going into large scale spraying. When adding soap as an emulsifier, use a potash-based one such as gun soap (Kenya).
  • Wear protective clothing while applying the extract. 
  • Wash your hands after handling the plant extract.

3. How to Prepare Neem Water Extracts

Neem fruits
(c) A.M.Varela

How to prepare neem water extracts from neem seeds:

Neem seeds
Neem seeds
(c) Courtesy EcoPort (http://www.ecoport.org): Dr. Pankaj Oudhia

Neem water can be stored and will remain effective for 3 to 6 days if it is kept in the dark.

1. Collect fallen neem fruits from underneath the trees. 
2. Remove the flesh from the seeds and wash away any remaining shreds. In some regions in Africa such as the Indian Ocean Coast in Kenya and Tanzania the seeds need not be taken off the tree or pulped when collected, as large colonies of fruit bats pluck the ripe fruit off the tree, during the night, suck off the sweet outer skin and then spit out the seed, which can be found lying under the trees the next morning. 
3. Dry the seeds in airy conditions (in sacks or baskets) to avoid formation of mould.
4. When needed, shell the seeds, grate them finely, and soak them overnight in a cloth suspended in a barrel of water. Dosage: 50g of neem powder per litre of water. This solution is then sprayed on infested plants. 

Removing pulp
(c) A.M. Varela

Detailed recipe to prepare 10 litres of Neem Seed Kernel Extract (NSKE): 
1. Grind 500 grams (g) of neem seed kernels in a mill or pound in a mortar.
2. Mix crushed neem seed with 10 litres of water. It is necessary to use a lot of water because the active ingredients do not dissolve easily. Stir the mixture well.
3. Leave to stand for at least 5 hours in a shady area.
4. Spray the neem water directly onto vegetables using a sprayer or straw brush. Neem water can be stored and will remain effective for 3 to 6 days if it is kept in the dark.

Neem seeds ready for processing
(c) A.M. Varela

It has been estimated that 20 to 30kg of neem seed (an average yield from 2 trees), prepared as neem water can treat 1 hectare of crop. 

Neem pesticides available in Kenya

1.) Neemros(r) and Neemroc(r): Locally produced pesticides. Produced by Saroneem Biopesticides Limited. Babadogo road, opposite Catholic Church.
P. O. Box 64373-00620 Nairobi. Contact: Mr. Dorian Rocco, Mobile: 0728592478, Email: saroneem@yahoo.com
2.) Achook: Manufactured in India and available in most Agrovet shops. 

Precautions in using Neem Extracts/Formulations:

1.) Neem is almost non-toxic to mammals and is biodegradable. It is used in India as an ingredient in toothpaste, soap, cosmetics, pharmaceuticals and cattle feed. The leaves are used for tea. However, the seeds and extracts of both neem and chinaberry trees are poisonous if consumed. Neem trees are very often confused with the Persian lilac or chinaberry tree a relative of neem, which thrives a in high altitudes, whereas neem thrives at low altitudes (up to 1200 m). 
2.) Because neem’s chemical structure is so complex (the tree has many different compounds, many functioning quite differently and on different parts of an insect’s life cycle and physiology), scientists believe it will take a long time for insects to develop resistance to it. However, to minimise the chance of affecting beneficials (natural enemies) and discouraging development of pest resistance, use neem sprays only when absolutely necessary, and only on plants you know are affected by pests.
3.) Neem extracts do not kill insect pests immediately. They change the feeding behaviour and life cycle of the pests until they are no longer able to live or reproduce. Effects are often not visible before 10 days after application. Consequently, severe pest attacks will not be controlled within time. For a reliable and satisfying control, neem extracts must be applied at an early stage of pest attack. 
4.) Neem products break down fairly quickly, usually within 5 to 7 days in sunlight and in the soil, so you may need to repeat the application during the growing season to deal with new pests that arrive from outside during this time.
5.) Neem works fastest during hot weather. Heavy rains within a few days of application may wash off the protective cover of neem on plants. Reapply if pests are a problem.
6.) If crops have to be watered, water should be targeted to the soil because water running over the leaves of sprayed plants may wash off the neem water extract.

4. Information Source Links

  • Ellis, B.W. and Bradley, F.M. (1992). The Organic Gardener’s Handbook of Natural Insect and Disease Control. Rodale Press. ISBN:0-87596-753-1 
  • HDRA. Leaflet The Neem tree, see also online under www.gardenorganic.org.uk
  • Hellpap, C. (1995). Practical results with neem products against insect pests, and probability of development of resistance. Pest of selected field crops. Corn. In The Neem tree- Source of Unique Natural Products for Integrated Pest Management, Medicine, Industry and Other Purposes. Ed. by H. Schmutterer. pp 385-389. ISBN: 3-527-30054-6.
    Lemmens, R.H.M.J., Soerianegara, I., Wong, W.C. (1995). Plant resources of Southeast Asia No. 5 (2). Timber trees: minor commercial timbers. Leiden, Netherlands: Backhuys Publishers. 
    Maundu, M. and Tangnas, B. (2005). Useful trees and shrubs for Kenya. World Agroforestry Center.
    Schmutterer, H. (Ed.) (1998). The Neem tree- Source of Unique Natural Products for Integrated Pest Management, Medicine, Industry and Other Purposes. pp 385-389. ISBN: 3-527-30054-6. 
    Siddiqui, K.M. (1995). Neem, its occurrence, growth and uses. Peshawar, Pakistan: Pakistan Forest Institute.
    Tewari D.N. (1992). Monograph on neem (Azadirachta indica A. Juss.). Dehra Dun, India: International Book Distributors. 
    Gianotti, R. L.; Bomblies, A.; Mustafa Dafalla, M. Issa-Arzika,I., Duchemin, J-B and Eltahir, E. AB. (2008). Efficacy of local neem extracts for sustainable malaria vector control in an African village. Malaria Journal 2008, 7:138 doi:10.1186/1475-2875-7-138. www.malariajournal.com

5. Local Reference Addresses for Neem Products

  • Health products and Neemros(r) and Neemroc(r), locally produced pesticides. Produced by Saroneem Biopesticides Limited. Babadogo road, opposite Catholic Church P. O. Box 64373-00620 Nairobi. Contact: Mr. Dorian Rocco Mobile: 072 859 2478, email:  saroneem@yahoo.com
Last updated on:

Wed, 02/28/2018 – 08:56

Copper fungicides in Kenya

Copper fungicides in Kenya

Credit: Biovision-Infonet

Copper fungicide (c) A.A. Seif, icipe

Recommended copper fungicides in organic farming are Bordeaux mix is a combination of copper sulphate and hydrated lime), Copper oxychloride and Copper hydroxide.

This datasheet includes methods of preparing and applying copper fungicides as well as a list of some of registered copper fungicides in Kenya.

1. Pesticides Permitted in Organic Gardening

If we think organic gardening means vegetables free of any chemical pesticides, we don’t have the story quite right.
Organic gardeners can use certain pesticides — chemicals that are derived from botanical and mineral-bearing sources. These chemicals may be highly toxic, but they break down more rapidly than common chemicals, such as the Sevins, Malathions and 2,4,Ds.

The use of botanical and mineral-bearing pesticides, even though some are toxic, also can be incorporated into an Integrated Pest Management (IPM) approach to growing crops. IPM relies on a variety of pest control means rather than on one product or method. The pesticides discussed below are appropriate to include in IPM programmes.

Just as the more common chemicals are given toxicity ratings — CAUTION, WARNING or DANGER — so are chemicals from botanical and mineral-bearing sources. “CAUTION” means low toxicity; “WARNING” means moderately toxic and “DANGER” means highly toxic. The toxicity rating for each pesticide is provided in the paragraphs below.

2. General information on copper

There are many copper compounds used as fungicides. Recommended is Bordeaux mix which is a combination of copper sulphate and hydrated lime (calcium hydroxide). . Other compounds include Copper oxychloride and Copper hydroxide. The latter two are now commonly used and are commercially available. 

Copper fungicides were formerly accepted in organic farming provided that the number of applications was strictly followed and a proper soil amendment is observed to prevent copper accumulation in the soil, and can still be accepted with permission from the certifying authority. 

In wet weather fungicides sprays should be applied as soon as the disease is observed or as soon as local experience suggests that weather conditions are favourable for disease development. 

Crop scouting should be used as a guide in making a decision on whether to apply a fungicide. And when applying a fungicides , safety procedures in application must be complied with, particularly, in use of protective clothing. Observe right dosage and prescribed pre-harvest intervals. Ask your local agricultural extentionist on locally registered fungicides.

Bordeaux mixture is primarily a fungicide that controls bacterial leaf spots, blights, anthracnoses, downy mildews and cankers. It also repels many insects. The compound is labelled for use on many vegetables, tree fruits and nut crops.

Bordeaux mixture, as with sulphur and lime sulphur, can be phytotoxic to plants. If applied in cool, wet weather, it may burn leaves or cause russeting of fruit.

Bordeaux mix spray

Materials needed to make a gallon mixture 

– 3 1/2 tbsp of copper sulphate
– 10 tbsp of hydrated lime
– 1 gallon of water (4 litres of water)
– Wooden stick
– Plastic bucket

How to prepare? 

1. Add copper sulphate and hydrated lime in water. Make sure to use plastic container
2. Stir well using a wooden sick or ladle
3. Protect self from direct contact with the solution

How to use? 

1. Spray plants thoroughly preferably early in the morning, in a dry and sunny day. In this way, the plants have the time to dry and the solution can not penetrate into the leaves’ tissues
2. Constantly shake the sprayer while in the process of application to prevent the solution from clogging

Pest controlled 

1. Flea beetles on tomatoes and potatoes
2. Anthracnose
3. Bacterial blight
4. Bacterial wilt
5. Black spot
6. Downy mildew
7.Early blight of potato and tomato
8. Late blight on solanaceous crops
9. Powdery mildew
10. Rust

Copper fungicides in the Kenya market

Copper products below listed are registered in Kenya by the Pest Control Products Board www.pcpb.or.ke. These products are readily available in most agro-vet shops in the country. It is advisable for organicfarmers to consult their respective certification agencies prior to use. According to the Soil Association (UK) www.soilassociation.org copper is “restricted” and can be only used where the need is recognized by the Soil Association Ltd (UK). Other organic certifying agents have differing rules.

Table 1 Copper fungicides commercially available in Kenya

3. Standard procedures for the preparation and application of homemade copper products

1. Monitor plants regularly and spray only when necessary.
2. Read and follow the label instructions carefully, particularly, dosage, pre-harvest intervals and safety measures. Ask for assistance from your local extension agriculture office, if unsure.
3. Spray in the early morning or late afternoon.
4. Wear protective clothing when handling pesticides and during application. Wash your hands after handling of pesticides and application. Do not eat, drink or smoke when handling and during application of synthetic pesticides including copper.
5. Do not have a direct contact with the crude extract while in the process of the preparation and during the application. 
6. Make sure that you place the product out of reach of children and house pets while leaving it overnight. 
7. Harvest all the mature and ripe fruits before product application. 
8. Always test the product formulation on a few infected plants first before going into large scale spraying. When adding soap as an emulsifier, use a potash-based one. Gun soap (Kenya) is recommended

4. Contacts

Agents / Distributors of Copper 

AMIRAN (K) LTD
Tel.: +254 (20) 6907000
Mobile: +254 719 095 000
Email: amiran@amirankenya.com / pr@amirankenya.com
Website: www.amirankenya.com

ANSET INTERNATIONAL LTD
Tel.: +254 (20) 2726868
Email:  tesna@ansetintl.com

BIOMEDICA LABORATORIES LTD
Tel.: +254 (20) 3518254 / 0727 034 566
Website: www.bio-medica.co.ke

CITY FARMING LTD
Tel.: +254 (20) 551462/3/ 0722 565 609/  0716 760 655
Email: info@cityfarm.co.keWebsite: www.cityfarm.co.ke

FARMCHEM (K) LTD
Tel.: +254 (20) 2409661 
Mobile: +254 722 520 837 / +254 733 520 837
Email:  farmchem@farmchemafrica.com
Website: www.farmchemafrica.com

HYGROTECH (K) LTD
Tel.: +254 (0) 722 205 148
Email: (Contact) :  info@hygrotech.co.keWebsite: www.hygrotech.co.ke

KIJANI AGENCIES LTD
P.O. Box 13980-00800
Nairobi

ORION (EA) LTD
Tel.: +254 (20) 62361/75895/75896
Email: orion@orioneastafrica.co.keWebsite: www.orioneastafrica.co.ke

OSHO CHEMICAL INDUSTRIES LTD
Tel.: +254 (20) 3912000
Mobile: +254 (0) 711 045 000/ 732 167 000
Email: oshochem@oshochem.com
Website:  www.oshochem.com

SAROC LTD, Nairobi
Tel.: +254 (20) 558831/554370

TWIGA CHEMICAL INDUSTRIES LTD
Tel.: +254 (20) 3942000/39423000
Email: info@twiga_chemicals.com
Website: www.twigachemicals.com

5. Information Source Links 

  • OISAT: Online Information Service for Non-Chemical Pest Management in the Tropics. www.oisat.org
Last updated on:

Mon, 11/26/2018 – 11:26

Bio-fumigation

Bio-fumigation

Credit: Biovision-Infonet

Mexican marigold (Tagetes minuta) has been successfully used in bio-fumigation against root-knot nematodes by a Kenyan farmer.
(c) Courtesy EcoPort (http://www.ecoport.org): R.P. Ellis

Bio-fumigation can be used against the following pests :Root-knot-nematodes and Bacterial wilt

1. General Information on Bio-fumigation

Bio-fumigation is based on incorporating soil amendment (fresh plant mass, manure) into the soil, which will release chemical substances, known as isothiocyanates (ITC’s), able to suppress soil-borne pests and diseases, plus a soil heater to enhance biological activities.

Plants from Cruciferae family (cabbage, radish, cauliflower etc.) release large amount of these toxic to soil-borne pests and diseases substances – in the soil and are considered the best material for bio-fumigation. 
How to do it:

  • Incorporate the fresh mass into the soil. This can be done directly if the mass is coming from grown crop or plant mass taken from elsewhere and brought into the plot or field. If the mass is transported to the field, the soil should be well prepared before the incorporation. During transportation and storage of these organic materials in the field, care must be taken not to lose the gases produced from biodegradation, by covering the piles of the bio-fumigant with plastic until the time of application. 
    A dose of 50 t/ha is recommended, although when problems with nematodes or fungi are very serious, 100 t/ha should be applied, a dose that can be reduced by choosing a cultivation techniques such as application in furrows. 
    The bio-fumigant should be distributed uniformly, so that no concentration of pathogens will appear that could create problems for the crop. Once the biofumigant is distributed, it should be incorporated immediately into the soil.
    Water the field, if possible by sprinkling, until the soil is saturated, although watering can be done by flooding, or drip irrigation can be installed.
    Cover the soil surface tightly with a transparent plastic film for at least 2 weeks to retain the gases produced from the biodegradation of the organic matter. This could be the same plastic as the one used for soil solarisation. 
    The film is removed 3-4 weeks after and the soil slightly removed in order to permit the gases to escape from soil.
    Planting of the interested crop can be done 24 hours later. 

2. Using Bio-fumigation against Nematodes

Different mustards (e.g. Brassica juncea var integrifolia or Brassica juncea var juncea) should be used as intercrop on infested fields. As soon as mustards are flowering they are mulched and incorporated into the soil. While incorporated plant parts are decomposing in a moist soil, nematicidal compounds of this decomposing process do kill nematodes. Two weeks after incorporating plant material into the soil a new crop can be planted or sown (it takes about 2 weeks for the plant material to decompose and stop releasing phytotoxic substances = chemicals poisonous to plants). (Eric Wyss, Personal communication) 

Mexican marigold, also known as Tagetes, has been successfully used in the control of root-knot nematode in roses by a Kenyan Farmer (Report on ToT for Alternatives to the Use of Methyl Bromide for Soil Fumigation in Brazil and Kenya). 

It is recommended to alternate the use of agricultural residues with green manure, especially from brassicae, using 5-8 kg square-metres of green matter, although combinations of legumes and grass can be applied. In the case of the use of green manure cultivated in the same field, fast growing plants should be used to be incorporated at least 30 days after having been planted, to avoid the increase of pathogen populations. Planting mustard after bio-fumigation can serve as bio-indicators of possible phytotoxicity, because the germination of their seeds is sensitive to phytotoxic substances. At the same time they are very sensitive to nematodes and permit the detection of areas in the crop where biofumigation is not effective. They act like trap plants, and like bio-fumigants when incorporated into the soil. 

In Spain, successful application of bio-fumigation was achieved in strawberries, peppers, cucurbits, tomato, brassicae, cut flowers, citrus and banana. Bio-fumigation has also been recently applied to Swiss chard and carrot crops. The most utilized biofumigants have been goat, sheep and cow manure, and residues from rice, mushroom, brassicae and gardens. 

The effectiveness of bio-fumigation in controlling nematodes, fungi insects, bacteria, and weeds is nearly the same as with the use of conventional pesticides. Bio-fumigation may also regulate viral problems by controlling vector organisms. 

(FAO, Global report on validated alternatives to the use of methyl bromide for soil fumigation)

3. Biofumigation against Bacterial Wilt

From 1999 research on using bio-fumigation for control of bacterial wilt has been carried out in Australia and the Philippines by the Australian Centre for International Agricultural Research (ACIAR). The Centre with collaborators have been working to identify suitable brassicas for tropical environments and to evaluate them in the field, initially on experimental farms and more recently on commercial farms and smallholder farmers fields. There are many varieties and they differ enourmously in the level of disease-suppressing chemicals they produce.

In recent years Australian banana growers have started growing brassica green manures for nematode control, and in the US farmers are using mustard green manure crops to replace synthetic fumigation for potatoes with huge savings on costs.

Growing of radish, mustard and broccoli have reduced bacterial wilt significantly (50-60%) in most of the experiments, though researchers believe the treatment is more effective on sandy soil than on heavy clay soil.

How do we get the useful chemicals out of the plant tissue? 

The most effective according to researchers is to disrupt the plant cells, by freezing or complete maceration. This will give the best bio-fumigation effect, but equipment to do this is not always available. A field rotavator used for chopping the plant material and incorporating it into the soil is second best. The rotavation effect can be duplicated by hand chopping the plant material before digging it into the soil but this is very labour demanding. 

The project also discovered that other large incorporations of green manure will suppress bacterial wilt. An example is mentioned of sweet potato leaves giving good control as well.
In Northern Australia, results in some field trials have been excellent. A plot with a high level infection of bacterial wilt was planted with tomatoes. An untreated block yielded less than 2 tons of tomatoes/ha, while the area where brassica green manure had been applied yielded up to 20 tons/ha of tomatoes and had correspondingly lower levels of bacterial wilt.

4. Information Source Links

  • FAO: Global report on validated alternatives to the use of methyl bromide for soil fumigation. 
  • Taylor, Robin. Mustard Cuts the Bacterial Wilt. Article in ‘Partners in Research for Development’ summer 2005-06 ACIAR. www.aciar.gov.au
Last updated on:

Wed, 02/07/2018 – 19:48Unless otherwise stated, all content on the Infonet Biovision Website is licensed under a Creative Commons License

Biopesticides in Kenya

Biopesticides in Kenya

Credit:Biovision-Infonet

Biopesticides include naturally occurring substances that control pests (biochemical pesticides) and microorganisms that control pests (microbial pesticides).

This datasheet includes a list of some of the registered biopesticides available in Kenya

1. Biopesticides in Kenya

Biopesticides are derived from micro-organisms (bacteria, fungi, viruses, etc), plants (neem, pyrethrum, etc) and natural enemies of pests (parasitoids, predators, and pathogens). Also included under biopesticides are semiochemicals (e.g. insect sex pheromes), enzymes (proteins) and natural plant regulators and insect growth regulators. Table 1 and Table 2 depict biocontrol agents (products derived from micro-organisms and natural enemies) and botanical pesticides (derived from plants), respectively. These biopesticides are registered in Kenya by the Pesticide Control Products Board (www.pcbp.go.ke) For more information refer to PCPB  website.

 Biopesticides (biocontrol agents) available in Kenya 

Name: Amblytech Active substances of products: Amblyseius californicus (predatory mite). Target Pest/Disease:Natural enemy for control of red spider mites (Tetranchus urticae) on vegetables and roses. Agent/Distributor:Flamingo Horticulture (K) Ltd, Naivasha

Name: Amblytech C Active substances of products: Amblyseius cucumeris (predatory mite), Target Pest/Disease:Bioagent for control of thrips and spider mites on flowers in greenhouses. Agent/Distributor:Flamingo Horticulture (K) Ltd, Naivasha 

Name: Aphitech Active substances of products: Aphididius transcapicus (parasitic wasp). Target Pest/Disease: Natural enemy for control of aphids (Aphis spp. and Acrosiphum spp. on vegetables. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: Vectonil 50 WP. Active substances of products: Bacillus thuringiensis. Target Pest/Disease: Larvicide to control mosquito larvae in breeding sites . Agent/Distributor: Osho Chemicals Industries Ltd  

Name: BioDewcon 2% WP . Active substances of products: Ampelomyces quisqualis (fungus).Target Pest/Disease: Fungicide for control of powdery and downy mildew on courgettes and snowpeas Agent/Distributor: Osho Chemical Industries Ltd

Name: BioCatch 1.15 WP.Active substances of products: Verticillium lecanii (fungus). Target Pest/Disease: Insecticide for control of aphids and whiteflies on roses, French beans and tomatoes. Agent/Distributor: Osho Chemical Industries Ltd

Name: Biokil WP. Active substances of products: Bacillus thuringiensis var. kurstaki (bacterium). Target Pest/Disease: Insecticide for control of thrips and African bollworms on French beans. Agent/Distributor: Agrifarm Biologicals Ltd

Name: Bio-Nematon 1.15 WP. Active substances of products: Paecilomyces lilacinus (fungus). Target Pest/Disease: Nematicide for control of Root-knot nematodes in French beans, roses and tomatoes. Agent/Distributor: Osho Chemical Industries Ltd

Name: Bio-Power 1.15 WP. Active substances of products: Beauveria bassiana Strain GHA (fungus). Target Pest/Disease: Insecticide for control of aphids and diamondback moth on cabbages. Agent/Distributor: Osho Chemical Industries Ltd

Name: Botanigard ES. Active substances of products: Beauveria bassiana Strain GHA (fungus). Target Pest/Disease: Biopesticide for control of sucking insects (aphids, thrips and whiteflies) on French beans and Snow peas. Agent/Distributor: Amiran (K) Ltd

Name: Delfin 6.4 WG. Active substances of products: Bacillus thuringiensis var. kurstaki Strain SA-11 (bacterium). Target Pest/Disease: Selective biological larvicide for control of Diamondback moth on brassicas and giant looper on coffee. Agent/Distributor: Sineria (K) Ltd

Name: Diglytech. Active substances of products: Diglyphus isaea (parasitic wasp). Target Pest/Disease: Natural enemy for control of leafminers (Liriomyza spp.) on flowers and vegetables. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: Dipel 2X. Active substances of products: Bacillus thuringiensis var. kurstaki Strain ABTS-351 (bacterium). Target Pest/Disease: Lepidopteran larvae (caterpillars) in coffee and horticultural crops . Agent/Distributor: Safina (EA). Ltd 

Name: Dipel DF. Active substances of products: Bacillus thuringiensis var. kurstaki Strain ABTS-351 (bacterium). Target Pest/Disease: Selective biological larvicide for control of  Lepidopteran larvae (caterpillars) (Helicoverpa armigera; Spodoptera exigua) plus leaf-rollers on carnation and roses. Agent/Distributor: Safina (EA). Ltd

Name: Ditera DC. Active substances of products: Myrothecium verrucaria (fungus). Target Pest/Disease: Nematodes in ornamentals. Agent/Distributor: Safina (EA). Ltd 

Name: Eco-T WP. Active substances of products: Trichoderma harzianum Strain k.d. (fungus). Target Pest/Disease: Fungicide for control of soil-borne diseases (Fusarium, Pythium and Rhizoctonia).Agent/Distributor: Madumbi East Africa Ltd

Name: Encartech. Active substances of products: Encarsia formosa (parasitic wasp). Target Pest/Disease: Natural enemy of whiteflies (Trialeurodes vaporariorum and Bemisia tabaci) in greenhouses. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: Ercal. Active substances of products: Eretmocerus eremicus (parasitic wasp). Target Pest/Disease: Biological control agent for control of whiteflies (Trialeurodes vaporariorum and Bemisia tabaci) in greenhouses. Agent/Distributor: Koppert Biological Systems (K) Ltd 

Name: Xentar. Active substances of products: Bacillus thuringiensis var. aizawai (bacterium). Target Pest/Disease: Biological insecticide for control of giant looper in coffee. Agent/Distributor: Safina (EA) Ltd 

Name: Halt 50 WP. Active substances of products: Bacillus thuringiensis var. kurstaki (bacterium). Target Pest/Disease: Insecticide for control oDiamondback moth in brassicas and caterpillars on roses. Agent/Distributor: Osho Chemical Industries Ltd

Name: Nematech WG. Active substances of products: Steinernema feltiae (nematode). Target Pest/Disease: Biopesticide to control thrips, leafminers, cutworms and sciarid flies on carnations. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: Real Phytoseiulus. Active substances of products: Phytoseiulus persimilis (predatory mite). Target Pest/Disease: Macrobial pesticide for control of red spider mites on roses and French beans. Agent/Distributor: Real IPM (K) Ltd 

Name: Phytotech. Active substances of products: Phytoseiulus persimilis (predatory mite). Target Pest/Disease: Natural enemy for control of spider mites (Tetranychus urticae) in vegetables and roses. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: PL-Plus. Active substances of products: Paecilomyces lilacinus (fungus). Target Pest/Disease: Biopesticide for control of nematodes in roses. Agent/Distributor: Juanco SPS Ltd

Name: Planopar.  Active substances of products: Coccidoxenoida perminutus (parasitic wasp). Target Pest/Disease: Biological control agent for control of mealbugs on roses. Agent/Distributor: Koppert Biological Systems (K) Ltd 

Name: Real Phytoseiulus. Active substances of products: Phytoseiulus persimilis (predatory mite) Target Pest/Disease: Red spider mites on roses and French beans. Agent/Distributor: Real IPM Company (K) Ltd

Name: Rootgard. Active substances of products: Trichoderma harzianum Strain 21 (fungus). Target Pest/Disease: Soil-borne diseases (Fusarium spp.) in flowers (carnation) Agent/Distributor: Juanco SPS Ltd 

Name: Spical. Active substances of products: Amblyseius (Neaseilus) californicus (predatory mite). Target Pest/Disease: Biological control agent for control of red spider mites on roses. Agent/Distributor: Koppert Biological Systems (K) Ltd

Name: Spidex. Active substances of products: Phytoseiulus persimilis (predatory mite). Target Pest/Disease: Biological control agent for control of red spider mites on roses. Agent/Distributor: Koppert Biological Systems (K) Ltd

Name: Swirski-Mite. Active substances of products: Amblyseius swirskii (predatory mite) Target Pest/Disease: Macrobial pesticide for control of whiteflies on roses. Agent/Distributor: Koppert Biological Systems (K) Ltd 

Name: Thripex. Active substances of products: Amblyseius cucumeris (predatory mite). Target Pest/Disease: Biological control agent for control of flower thrips and spider mites on carnation grown in greenhouses. Agent/Distributor: Koppert Biological Systems (K) Ltd

Name: Thuricide HP. Active substances of products: Bacillus thuringiensis var. kurstaki (bacterium). Target Pest/Disease: Lepidopteran larvae (caterpillars) on vegetables and giant looper on coffee. Agent/Distributor: Farmchem (K) Ltd 

Name: Trianum-P 11.5 WP. Active substances of products: Trichoderma harzianum Rifai Strain KRL-AG2 (T22) (fungus). Target Pest/Disease: Biopesticide for control of soil-borne fungal diseases caused by Pythium, Rhizoctonia and Fusarium spp. in French beans and carnations. Agent/Distributor: Koppert Biological Systems (K) Ltd 

Name: Trichotech. Active substances of products: Trichoderma asperullum (fungus). Target Pest/Disease: Biopesticide for control of soil-borne fungal diseases caused by Pythium, Rhizoctonia and Fusarium spp. in French beans, or the control of fusarium wilt in carnations. Agent/Distributor: Flamingo Horticulture (K) Ltd, Naivasha

Name: Xentari. Active substances of products: Bacillus thuringiensis var. aizawai (bacterium). Target Pest/Disease: Insecticide for control of giant looper on coffee and for the control of caterpillars on Roses and Carnations. Agent/Distributor: Safina (EA) Ltd

Abbreviations

  • DF: Dry flowable
  • EC: Emulsifiable concentrate
  • SC: Suspension concentrate
  • WG: Water dispersible granule
  • WP: Wettable powder

2. Information source links

Fully registered pest control products in Kenya, Version 1- 2018. Website www.pcpb.go.ke

3. Contacts

Agents / Distributors of Biopesticides in Kenya  AGRICULTURE AND FOOD AUTHORITY- PYRETHRUM & INDUSTRIAL CROPS DIRECTORATE
Mobile: +254 722 200 556/734 600 944
Email: info@afa.go.ke
Website: www.agricultureauthority.go.ke AMIRAN (K) LTD
Mobile: +254 719 095 000/0800 720720
Email: pr@amirankenya.com
Website: www.amirankenya.comDUDUTECH (K) LTD
Tel.: +254 (50) 2020859
Email: info@dudutech.com
Website: www.dudutech.comKAPI LTDTel.: +254 (51) 2217134 / 2217228/2215308
Mobile: +254 733 640 065
Email:  info@kapiltd.co.keWebsite:www.kapikenya.comKOPPERT BIOLOGICAL SYSTEMS (K) LTD
Tel.: +254 (20) 2021918
Mobile: +254 724 256 524
Email: cmacharia@koppert.co.ke
Website: www.koppert.co.ke / www.koppert.comJUANCO SPS LTD
Tel.: +254 (20) 2088754/5/6
Mobile: +254 7222 207 805/6
Email: info@juancogroup.com
Website: www.juancogroup.com

ORGANIX LTDTel.: +254 (20) 3566241/2
Mobile: +254 720 937 537 / +254 735 712 090
Website: www.organix-agro.comOSHO CHEMICAL INDUSTRIES LTD
Tel.: +254 (20) 3912000
Mobile: +254 0711 045 000/0732 167 000
Email: oshochem@oshochem.com
Website: www.oshochem.comREAL IPM COMPANY (K) LTD
Mobile: +254 725 806 086
Email: info@realipm.com
Website: www.realipm.comSAFINA (EA) LTD
Tel.: +254 (20) 2210417
Email: safina@wananchi.com

SINERIA (EA) LTD
Mobile: +254 720 848 255
Email: info@sineria.com
Website: www.sineria.com

Last updated on:

Mon, 05/13/2019 – 08:34

Bt (Bacillus thuringiensis)

Bt (Bacillus thuringiensis)

Credit: Biovision-Infonet

Bacillus thuringiensis (Bt). Bt is a bacterium and is not visible to the naked eye.
(c) Courtesy EcoPort (http://www.ecoport.org): Daniel Anand Raj,

Scientific name: Bacillus thuringiensis Bt can be used against the following pests :African armyworm, African bollworm, Bean armyworm. Beet armyworm, Cabbage webworm, Cabbage moth, Cabbage looper, Cotton leafworm, Diamondback moth, Giant looper, Green looper, Spiny bollworm, Spotted bollworm, Pod borers, Tomato looper

1. General information on Bacillus thuringiensis(Bt)

Bacillus thuringiensis is a naturally occurring soil bacterium that causes disease on insect pests. It is accepted in organic farming and is considered ideal for pest management due to its low cost, ease of application, high virulence and narrow host specificity. Thus, Bacillus thuringiensis is regarded as environmentally friendly with no toxic effects on natural enemies and humans. The activity of Bacillus thuringiensis is due to toxins produced by this bacterium.
Bacillus thuringiensis is commercially available in most agricultural suppliers. It is sold in various formulations (spray, dust, and granule) and strains (Bt. tenebrionis, Bt. kurstaki, Bt. israelensis, Bt. aizawai, Bt. san diego). Bt. products in Kenya are sold under the following commercial names: Dipell(r), Javelinl(r), Thuricidel(r), and Xentaril(r). Note that not all Bacillus thuringiensis can be used for control of caterpillars. Bt. israelensis is used for control of mosquitoes and Bt. tenebrionis for control of beetles. 

How does it work?

Bacillus thuringiensis must be ingested by a susceptible host to be effective. When ingested, Bacillus thuringiensis produces proteins that react with the cells of the stomach lining. These (proteins) poison and paralyse the insect’s digestive system causing the insect to stop feeding within hours. Bt-infested insects will live for several days but will cause no further damage to the plant. They will die eventually from starvation. 

How to use Bacillus thuringiensis (Bt)

1. Spray thoroughly, covering all the plant surfaces. 
2. Apply when larvae are less than 5 mm long or when the eggs begin to hatch. Bt works best on young larvae. 
3. In the hot tropics, it is more effective to spray Bt in the late afternoon as there are longer and cooler hours ahead. This enables Bt to remain longer on the leaves’ surfaces. Bt survives better in cooler temperature. Whereas, spraying in the morning provides a shorter and hotter environment. 
4. Do not mix the Bt concentrate with alkaline water (pH 8 or higher). Alkalinity reduces its effectiveness. To make the water acidic, add a few tablespoons of white vinegar in a gallon of water before adding Bt.

2. Information Source Links 

  • ICIPE: www.icipe.org 
  • OISAT: Online Information Service for Non-Chemical Pest Management in the Tropics. www.oisat.org
Last updated on:

Tue, 03/06/2018 – 19:08

Spider Mites

Spider Mites (General)

Credits:Biovision-Infonet

Two-spotted spider mite (Tetranychus urticae). The adult female is 0.6 mm long. The male is smaller.
(c) Image supplied by Warwick HRI, University of Warwick
Spider mites on cotton leaf. They are very tiny (they rarely exceed a size of 0.5 mm)
(c) O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org
Spider mites on tomato. Note the mites and their webbing visible beetween the leaves.
(c) Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org

1. Geographical Distribution in Africa

Geographical Distribution of Spider mites in Africa (red marked). Updated on 11 July 2019. Source CABI
Fruit damaged by spider mites.
(c) A. M. Varela, icipe

2. General Information on Pest and Damage

Generally, spider mites prefer the undersides of leaves, but in severe infestation will occur on both leaf surfaces as well as on the stems and fruits. They suck the sap of plant tissues. Infestations are most serious in hot and dry conditions. Because they multiply very fast they are able to destroy plants within a short period of time. Spider mites spin silk threads that anchor them and their eggs to the plant. The fine web produced by spider mites protects them from some of their enemies and even from pesticide applications. 

The most destructive spider mite species in East Africa is the tobacco or tomato red spider mite (Tetranychus evansi). This mite is a very serious pest in tomato crops and other members of the Solanaceae family (tomato, potato, eggplant, tobacco and wild plants and weeds like black nightshade, bitter apple and wild gooseberry). This species originates from Brazil, South America and was accidentally introduced into Southern Africa during the 80’s. 

Since then this spider mite has slowly been moving northwards. Nowadays it is one of the major constraints into tomato production in Kenya, Mozambique, Malawi, Namibia, Zimbabwe and Zambia. When left uncontrolled the farmer can loose his or her production within a week time. 

The two spotted spider mite (Tetranychus urticae) and the carmine spider mite (Tetranychus cinnabarinus) cause yield loss on tomatoes only inexceptional cases such as: very hot and dry conditions, destruction of natural enemies, the presence of other highly infested crops in the near vicinity and insufficient water supply to the crop.

Damage by spider mites on beans is most severe when mite feeding occurs early in the vegetative period.

Another important species is the cassava green mite (Mononychellus tanajoa), an important pest of cassava. This mite is green in colour at a young age turning yellowish as adult. It was accidentally introduced from South America and its rapid spread becoming one of the most important pests of cassava in Africa.

The cotton red mite (Oligonychus gossypii) is a widely distributed mite in Africa. It is commonly found on cassava, mainly during the dry season, but it is much less economically important than the cassava green mite. It also attacks cotton, citrus, peach, papaya, beans, okra, peanut, and ornamentals.

The coffee red mite (Oligonychus coffeae) may be a pest of unshaded coffee and tea in localised attacks during the dry season. They attack the upper surface of mature leaves. As a result the upper surface of fully hardened leaves turn rusty, purple or yellow brown colour. Under drought stress young leaves may also be attacked.

Host range

Spider mites have been recorded from a wide range of wild and cultivated plants – including beans, cassava, cotton, citrus, okra, tomato, papaya, potato, tobacco, strawberry various cucurbits and legumes. 

Symptoms

First symptoms are usually clusters of yellow spots on the upper surface of leaves, which may also appear chlorotic. This gives the leaf a speckled or mottled appearance. Feeding by spider mites may lead to a change of leaf colour in some plants such as okra, cotton, coffee, tea and some ornamentals. Attacked leaves turn bronze, or rusty, purple or yellow brown colour. Spider mites and webbing are present on the lower leaf surface, which may appear tan or yellow and have a crusty texture. 

Feeding by the cassava green mite leads to stunted and deformed cassava leaves. Severe attacks cause the terminal leaves to die and drop, and the shoot tip looks like a “candle stick”. 

Under severe infestations leaves redden, whither, and drop. Some spider mites (e.g. T. evansi) produce large amount of webbing. Heavy infestation will result in a fine cobwebby appearance on the leaves and the whole plant. Plants die when infestation is severe. 

Initial infestation of spider mites on tomato. Note mites seen as reddish specks on underside of a tomato leaflet.
(c) A. M. Varela, icipe
Spider mites on tomato. Note the mites and their webbing visible between the leaves.
(c) Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org

Affected plant stages

Vegetative growing stage, flowering stage, post-harvest 
 

Affected plant parts

Leaves, inflorescences, fruits. 

Symptoms by affected plant part

Leaves: lesions, abnormal colours, abnormal leaf fall, yellowed or dead.
Inflorescences: yellow or abnormal colour, abnormal flower fall, premature fall of young fruits.
 

3. Biology and Ecology of Spider Mites

Introduction

Mites are not insects. They are related to spiders and ticks and they are very tiny (they rarely exceed a size of 0.5 mm). Spider mites are normally active within a temperature range of 16 to 37degC. They are more numerous in hot, dry weather. They are normally less numerous after rains. Wind plays an important role in the dispersal of spider mites. The lifecycle of a spider mite may take 10 to 30 days depending on temperature. It includes five stages: egg, larva (first instar) two nymphal stages and adult. A female may lay over 100 eggs during its lifespan. Spider mites spin silk threads that anchor themselves and their eggs to the plant. This silk protects them from some of their enemies and even from pesticide applications. 

Description

Eggs are tiny, spherical, pale-white, and are laid on the undersides of leaves often under the webbings. They can only be seen with a magnifying lens. Eggs hatch in 4 or 5 days. 

The larvae are light green or pinkish, slightly larger than the eggs and have six legs. 

The nymphs look similar to the adults but are smaller. They are green or red in colour and have eight legs.

The adults are oval and have eight legs. They are very tiny (they rarely exceed a size of 0.5 mm) resembling tiny moving dots to the naked eye. The male is usually smaller than the female and have a more pointed abdomen. Spider mites are variable in colour depending on the species. Many of the species are bright red in colour; and that is reason why spider mites are sometimes referred to as red spider mites. Others are yellowish, greenish, pinkish, orange or reddish in colour. The two-spotted spider mite has a large dark blotch on each side of the body. 

Female of the cassava green mite (Mononychellus tanajoa),
real size 0.8 mm
(c) F. Haas, icipe
Eggs and larva of the cassava green mite (Mononychellus tanajoa), real size 0.2 mm
(c) F. Haas, icipe
Male of the cassava green mite. (Mononychellus tanajoa), real size 0.8 mm
(c) F. Haas, icipe

Major species of spider mites in Africa:

  • The common/two-spotted spider mite (Tetranychus urticae)
  • The tobacco red spider mite (Tetranychus evansi)
  • The carmine red spider mite or common red spider mite (Tetranychus cinnabarinus)
  • The cassava green mite (Mononychellus tanajoa)
  • The coffee red mite (Oligonychus coffeae)
  • The cotton red mite (Oligonychus gossypii )

4. Pest and Disease Management

Pest and disease management: General illustration of the concept of Infonet-biovision

This illustration shows the methods promoted on infonet-biovision. The methods shown at the top have a long-term effect, while methods shown at the bottom have a short-term effect. In organic farming systems, methods with a long-term effect are the basis of crop production and should be with preference. On the other hand methods with a short-term effect should be used in emergencies only. On infonet we do not promote synthetic pesticides. 
 Further below you find concrete preventive and curative methods against Spider mites. 

5. Cultural practices

Monitoring

Inspecting your field regularly is very important, since the population build up of the mites is very rapid. At the beginning of the infestation the distribution of mites is very patchy. Control must start early. It is very difficult to control the mite population once they are established. A recommended monitoring method for mites on tomato is: 

Select randomly 20 tomato plants and access the level of damage caused by the mites of 3 leaflets/plant by using a damage leaf index ranking from 1 to 5 (1 is few yellow spots, 5 is leaf totally covered with spots, dry patches occur). Once the average damage level exceeds the first rank, control measures should start.

Less experienced farmers sometimes have difficulties with early identification of the mites, since the symptoms resemble a nutrient deficiency or plant disease. Close inspection of the underside of affected leaves shows mites as tiny moving specks (red or yellow-greenish depending on the species) and whitish particles (shed skins of mites).

Further cultural practices are:

  • Site nurseries away from infested crops and avoid planting next to infested fields.
  • Grow healthy crops; avoid water and nutrient stress. Apply mulch and incorporate organic matter into the soil to improve the water holding capacity and reduce evaporation.
  • Keep perennial hedges such as pigeon peas, they are said to encourage predatory mites, which predate on spider mites.
  • Uproot and burn infested plants. This can be successful during the early stages of infestation when the mites concentrate on a few plants.
  • Keep the field free of weeds.
  • Remove and burn infested crop residues immediately after harvest
  • Mites favour dry and hot conditions. Influencing the microclimate by reducing the planting distance is reported to suppress spider mite populations. However, this could also enhance fungal diseases, so care should be taken.
  • When moving through the crop for weeding, pruning, harvesting or any other field work, always leave the infested area until last in order to minimise the spread of mites on clothing or farm tools

6. Biological pest control

Natural enemies

A range of natural enemies attacks spider mites. The most important are predatory mites, predatory beetles such as small staphilinidae (Oligota spp), and ladybird beetles, lacewings, predatory thrips, anthocorid bugs (Orius spp), mirid bugs, and predatory flies such as cecydomyiid and hoverflies. 

Naturally occurring predators are in most cases capable of controlling infestations of the two-spotted spider mite and the carmine red spider mite, provided natural enemies are not disturbed by the severe use of broad-spectrum pesticides – and if the crop is irrigated properly. 

This is not the case for spider mites that have been accidentally introduced from other continents. Thus, few natural enemies are known to feed on the tobacco spider mite in Africa. In contrast, natural enemies keep this mite under control in his home region (Brazil). ICIPE has recently conducted experimental releases of a predatory mite (Phytoseiulus longipes) introduced from Brazil into Kenya (personal communication, Markus Knapp, icipe). 

The cassava green mite has been effectively controlled by predatory mites (mainly Typhlodromalus aripo and T. manihoti) introduced from South America, the home of the cassava green mite (Yaninek and Hanna, 2003). 

Several natural enemies of spider mites are commercially available worldwide. The most common is the predacious mite Phytoseiulus persimilis. This predatory mite, widely used for control of the two-spotted spider mite, is present in Kenya and it is commercially available. Suitable release rates and timings vary with the crop. In areas where the mite has been established, augmentative releases are required to maintain control.

Tetranychus predators – predatory mites (orange-red individuals)(Phytoseiulus persimilis) in a colony of the two-spotted spider mite (Tetranychus urticae). Spider mites are very tiny, they rarely exceed a size of 0.5 mm.
(c) Warwick HRI, University of Warwick.
Adult of the predatory beetle Oligota sp. a natural enemy of mites.
(c) F. Haas, icipe

According to RealIPM newsletter of Jan 2008, the horticultural export company Oserian has now been spider mite free for 1 1/2 years using Phytoseiulud persimilis and integrated management saving large amounts on money on acaricides and getting much better quality roses. The same predatory mite is also effective for spider mites on French beans both in green house and field conditions. Available from Real IPM and Koppert(Ltd). See contacts below.
 

7. Biopesticides and physical methods

Neem

Neem products, in particular oil formulations give reasonable control of spider mites. Though neem does have some systemic effect in plants, spray it as other contact insecticides, ensuring thorough spray coverage and targeting the undersides of the leaves where spider mites tend to cluster. Neemcommercial products are available in Kenya.

Soap spray

Apply on the infested plants thoroughly, including the undersides of the leaves. Spray early in the morning or late afternoon. 
Precaution:
Soap spray may injure foliage. Test these sprays on few leaves before applying to the entire field. It may take 2 days for damage symptoms to appear.

Pyrethrum

Spray of natural commercial pyrethrum extracts such as “Flower DS(r)” (Kenya) control spider mites when applied on very early outbreaks (farmer experience, Kenya). Take care of beneficial insects, which are also killed by pyrethrum.  

Flour preparations

Flour mixed in water is said to be very effective against aphids and spider mites. It should be applied in the morning taking care to spray underside of leaves. As the heat of the sun increases, the mixture dries out and the insects are left encrusted in flour, shrivel and die. The coating of flour falls off the leaves so that their ability to photosynthesise is not essentially affected (Gabriele Stoll, 1988).

Glues

Any water-soluble glue, particularly those obtained from plants, for example glue (starch) obtained by boiling potatoes and cassava in water has been reported to suppress spider mites. Spray a weak solution to suffocate the insects. The strength of mixes varies greatly according to the glue available but the diluted solution should leave a thin skin coating the plant when the solution has dried (H. Elwell et. al, 1995). 

Others

The above mentioned and other natural control methods against spider mites are currently being tested in several Eastern and Southern African countries. Thus, the Mashare ADI (Agricultural Development Institute) in the Kavango Region in Namibia is carrying out tests with chilli, garlic and soap extracts, and a mixture of buttermilk and flour. The results are not available yet, however for the latest information, contact the Horticultural Section at Mashare ADI or the Kavango Horticultural Production and Marketing Project (KHPMproject@mweb.com.na). Botanicals such as neemand Tephrosia sp. are currently being evaluated in Malawi, Zimbabwe and Kenya. 

Lachlan Kenya Ltd currently markets an organically certified botanical product called Bio-cure, which according to Real IPM is much more effective against spider mites than pyrethrum. See reference addresses below.

Water

  • Overhead irrigation or hosing with a strong jet of water knocks off mites and destroys their webs. Be sure to spray the underneath of the leaves. However, this should be done early in the day to allow the foliage to dry. Wetness of the foliage for an extended period is conducive to development of fungal diseases.
  • Apply water to pathways and other dusty areas at regular intervals.

8. Information Source Links

  • CABI. (2005). Crop Protection Compendium, 2005 Edition. (c) CAB International Publishing. Wallingford, UK. www.cabi.org
  • EPPO. European and Mediterranean Plant Protection Organization www.eppo.org
  • Henry Elwell & Anita Maas. Natural Pest & Disease Control. Natural Farming Network, Zimbabwe, P.O.Box 301, Causeway, Harare 1995. ISBN: 0-7974-1429-0
  • Keizer, M. and Zuurbier, J. Red Spider Mite. Namibian crop pests.
  • OISAT. Online Information Service for Non-Chemical Pest Management in the Tropics. www.oisat.org
  • Seif, A.A., A.M. Varela, Loehr, B. and S. Michalik (2001). A Guide to IPM in French Beans Production with Emphasis on Kenya. pp. 88. ICIPE Science Press, Nairobi, Kenya. (ISBN: 92 9064 142 8). www.icipe.org
  • Stoll, Gabriele (1988). Natural Crop Protection on the Tropics. AGRECOLE. c/o OKOZENTRUM, CH-4438 Langenbruck, Switzerland.
  • Varela, A. M., Seif, A.A., and B. Loehr (2003). A Guide to IPM in Tomato Production in Eastern and Southern Africa. ICIPE Science Press, Nairobi, Kenya. ISBN: 92 9064 149 5.
  • Varela, A. M., and A.A., Seif. (2004). A Guide to IPM and Hygiene Standards in Okra Production in Kenya. ICIPE Science Press, Nairobi, Kenya ISBN: 92 9064 161 5

9. Contact Links

  •  The Real IPM Company (K) Ltd P O Box 4001-01002, Madaraka, Thika – 01002, Kenya. 254 (0)725 806 086, email: info@realipm.com, Web: www.realipm.com
  • Koppert Biological Systems (K) Ltd. 2nd Floor, Baobab House Westlands Office Park , Waiyaki Way P.O. Box 41852 – 00100, NAIROBI , KENYA . Tel. +254 20 2021918/ 4453780/1/2 Fax +254 20 4453783 Cell:+254 731 202191  Web: www.koppert.com
  • Lachlan Kenya Limited, P.O.Box 49470, 00100 Nairobi. Old Airport Road, off Mombasa road. Tel: +254 20 2073 912/3/4, 0722 209 474 . Fax: +254 2060 260. E-mail: lachlan@agriculture.co.ke.
Last updated on:

Thu, 07/11/2019 – 11:46

Diamondback Moth

Diamondback Moth

Credit: Biovision-Infonet

Diamondback moth adult. The adult is greyish brown with a 9 mm long body and a wingspan of about 1.2 to 1.5 cm
(c) A. M. Varela, icipe
Diamondback moth caterpillars feeding on kales
(c) A. M. Varela, icipe
Diamondback moth adult. The adult is greyish brown with a 9 mm long body and a wingspan of about 1.2 to 1.5 cm
(c) A. M. Varela, icipe
Diamondback moth caterpillar parasitised by Cotesia plutella. Note silky cocoon of the parasitoid near dead DBM caterpillar. The wasp larva emerges from the caterpillar and spins a white cocoon from which the adult wasp emerges.
(c) A. M. Varela, icipe

Diamondback moth young larvae
(c) Anne Bruntse, Biovision
Diamondback moth pupa is 5 to 6 mm long, about four times as long as the width. It is covered with a white silken cocoon. Initially pupa is pinkish-white to pinkish-yellow.
(c) MOFGA, Eric Sideman

1. Geographical Distribution in Africa

Cabbage damaged by diamondback moth
(c) A. M. Varela, icipe
 

2. General Information on Pest and Damage

Damage

Cabbage damaged by diamondback moth
(c) A. M. Varela, icipe

Throughout the world diamondback moth is considered the main insect pest of brassica crops, particularly cabbages, kales, broccoli and cauliflowers. The economic impact of diamondback moth is difficult to assess since it occurs in diverse small scale and large-scale production areas, but it has been known to completely destroy cabbage and kale crops. It is considered a major pest in all countries of the eastern and southern African region.

Host Range

Broccoli, cabbage, cauliflowers, and other brassica crops. In Kenya, diamondback moth has also been found feeding on peas. 
 Symptoms

Diamondback moth – Young caterpillars and their damage on kale.
(c) A.M. Varela, icipe

Newly hatched DBM caterpillars feed as leafminers inside the leaf tissue. Older caterpillars feed on all plant parts. They feed on the leaf tissue leaving the upper leaf surface intact. This type of damage is called “windowing”, since it gives the appearance of translucent windows on the leaf. In cases of severe infestation entire leaves could be damaged. Caterpillars and pupae are found on damaged leaves. Older caterpillars are often found around the growing bud of young plants. Their feeding can deform the plant. DBM caterpillars also feed on stems and pods. Heavy damage results in the marketable parts contaminated with excrement, which makes the produce unsaleable. 

Affected plant stages

Seedling stage, vegetative growing stage, flowering stage and fruiting stage. 
Affected plant parts:

Fruits/pods, growing points, inflorescence, leaves and stems.

3. Biology and Ecology of the Diamondback Moth

Eggs of the diamondback moth
(c) F. Haas, icipe

Eggs are tiny (less than 1 mm), flat and oval in shape, and yellowish in colour. They are laid singly or in groups of 2 to 3 along the veins on the upper and lower leaf surfaces. The eggs hatch in 3 to 8 days depending on the environmental conditions. 

Diamondback moth caterpillars feeding on kales
(c) A. M. Varela, icipe

Caterpillars are pale yellowish-green to green covered with fine, tiny scattered, erect hairs. Mature caterpillars are cigar-shaped and about 12 mm long. They have chewing mouth parts. 

The caterpillars go through four instars and complete their development and pupate in 10 to 28 days. Diamondback moth (DBM) caterpillars are easily identified because they wriggle violently when disturbed, drop from the plant suspended by a silken thread and finally climb their way back up and continue feeding.

Diamondback moth pupal colour changes to brown before adult emergence. The developing moth can be seen through the cocoon. The pupa is 5 to 6 mm long.
(c) A. M. Varela, icipe

Pupae are 5 to 6 mm long. Pupae are initially light green and turn brown as the adult moths become visible through the cocoon. They are covered with a loosely spun net-like cocoon that is attached to the leaves, stems or seed pods of the host plant. Cocoons are about 9 cm long. 

The moths emerge 3 to 15 days after pupation depending on the environmental conditions. 

Diamondback moth adult on cabbage leaf. The adult is greyish brown with a nine mm long body and a wings-
pan of about 1.2 to 1.5 cm
(c) Alton N. Sparks, Jr., The University of Georgia,www.insectimages.org

The adult is a small greyish-brown moth, approximately 8 to 9 mm long with a wingspan of 12 to 15 mm. It has diamond-shaped markings on the back when the wings are folded, which gives the common name to this insect. The moth folds its wings over the abdomen in a tent-like manner when resting. The wing tips are fringed with long hairs. Adult females can lay an average of 160 eggs during their lifespan of about 16 days. Moths lay eggs at night. The greatest number of eggs is laid the first nights after emergence, egg laying continues for about 10 days. In the field, moths will fly up out of the plant canopy when disturbed.

Diamondback moth infestations tend to be serious in the dry months. Heavy rains may reduce populations dramatically, thus this pest is less likely to be a problem in wet years and during rainy seasons. Diamondback moth populations can increase rapidly at temperatures above 26degC. 

4. Pest and Disease Management:

Pest and disease Management: General illustration of the concept of infonet-biovision

This illustration shows the methods promoted on infonet-biovision. The methods shown at the top have a long-term effect, while methods shown at the bottom have a short-term effect. In organic farming systems, methods with a long-term effect are the basis of crop production and should be of preference. On the other hand methods with a short-term effect should be used in emergencies only. On infonet we do not promote synthetic pesticides. 

Further below you find concrete preventive and curative methods against Diamondback moth (DBM).

5. Cultural practices

Monitoring

Inspect the crop regularly. Diamondback moth populations can increase rapidly in warm conditions. Therefore, it is important to scout for DBM moth regularly, at least twice a week. Diamondback moth caterpillars are detected by visual observations of the plant. (Adults can also be detected by the use of pheromone traps though they are not yet available in East Africa.) 

Scouting should begin when the plants are young; the earlier the pest is discovered, the easier it is to control. Plants should be checked thoroughly. Growing points should be carefully examined. Caterpillars that are inside the cabbage head are difficult to detect unless outer leaves are pulled back. When scouting, it is important to record presence of parasitic wasps and parasitised caterpillars. Please also refer to section on natural enemies under Biological Pest Control further down on this page. 
 Examples of economic thresholds

Economic thresholds for the diamondback moth have been developed in several countries. For example, in small cabbage plots (0.25 ha) in Honduras, it is recommended to sample at least 60 plants and the action threshold is one caterpillar per plant. Broccoli and cauliflower at the vegetative stage can support 30% defoliation. At harvest time, an infestation level of one caterpillar per head is the action threshold (Rueda and Shelton, 1995). In the Midwest (USA), the treatment threshold for caterpillars (including DBM) attacking cabbage is given as 10% of infested pants in the seedbed, 30% infested plants from transplant to cupping stage, 20% infested plants from cupping to early heading, and 10% infested plants at early heading to mature head stages. For processing cabbage, which will be trimmed and shredded, more injury is tolerable; treatment is advised at 75% infestation. The treatment thresholds for broccoli and cauliflower are: 10% plant infestation in the seedbed, 50% plant infestation from transplant to first flower, and 10% infestation from first flower to maturity (Foster and Flood, 1995).

These thresholds are given as examples. However, note that economic thresholds depend on many factors (crop stage, crop age, and economic and climatic conditions) and cannot be adopted without taking into consideration local conditions. 
 Sanitation

  • Start with a healthy crop. Place seedling beds away from production fields to minimise attack by the diamondback moth. Transplant only healthy seedlings, which are free of eggs, caterpillars and pupae of the diamondback moth and other pests.
  • Remove and destroy or plough down crop residues in seedling beds and production fields.

These practices will prevent build-up of the diamondback moth and migration to nearby fields.Crop rotation

Crop rotation can be effective in controlling the diamondback moth in semi-arid environments as there are only very few wild host plants. A significant reduction in the numbers of caterpillars can be achieved by having a break of 6 weeks or more where no brassica crops (cabbage, broccoli, cauliflower among others) are grown at all. 

It is important that all farmers in a locality, or at least close neighbours, follow crop rotation simultaneously. This break will disrupt the pest’s breeding cycle. Therefore, brassica crops planted after this break will be safe from the pest for sometime. However, this does not work in the highlands where large numbers of wild host plants are present in the surroundings of the fields throughout the year. 
 Intercropping, trap cropping

Planting rows of tomatoes alternately with rows of cabbage is reported to reduce damage but it does not prevent the attack completely. Kenya Institute of Organic Farming recommends this method as effective. In addition, cabbages would repel the tomato bollworm, making this practice serve a double purpose. 

Intercropping with chillies is said to repel diamondback moth adults (Dobson et al, 2002).

Trap crops such as mustard and rape can also be useful to reduce diamondback moth attacks. Fifteen rows of cabbage followed by mustard rows have been shown to be most effective (HDRA, 2000). Bold seeded Indian mustard could also be sown densely all around the area 10 days before the crucifers are planted. The plants attract up to 80% diamondback moths (IPM Bulletin of Pest Management, Undated). However, trap crops should be frequently monitored so as to control this pest before it can move to the main crop. Once the trap crop is infested it can be ploughed in or removed. Unattended trap crops can generate large populations of diamondback moth. 

Care is needed to manage intercrops in order to use them as part of a control practice (Shelton et al., 1995). 
 Irrigation

As with rain, frequent overhead irrigation disrupts moth activities and washes off caterpillars from the plants. However, use of sprinkler irrigation may lead to increase of diseases such as black rot and downy mildew.

6. Habitat Management

Habitat management

Managing the habitat or the way a crop is grown helps to prevent or reduce pest and disease. Mix cropping brassica crops with some other crops or plants (intercropping, trap crops, strip cropping) has been shown to reduce infestation by the diamondback moth. The plants to be grown together with the brassica crops need to be carefully selected. Oniona and tomatoes can be intercropped with brassicas.

Maintaining natural surroundings, including trees and shrubs help to conserve natural enemies by providing shelter and plenty of breeding places for them. Maintaining strips of local flowering plants in the vicinity of the brassica crops is useful for beneficial insects. Trap cropping with flowering mustard can also augment the number of beneficial insects in the trap crop and the neighbouring crops. 

7. Biological pest control

Natural enemies

Natural enemies (local and imported) can help to keep the pest at acceptable levels if they are conserved and their activity encouraged. Habitat management and avoidance of broad-spectrum insecticides early in the season, when the diamondback moth is present in low numbers may preserve natural enemies that can help keep diamondback moth and aphid populations under control later in the season. 

Many natural enemies prey on the diamondback moth at different stages of its life cycle. Birds and spiders feed on moths; ants, lacewings, wasps, and parasitic wasps among others attack the caterpillars. 

Numerous parasitic wasps attack diamondback moth. The most common are wasps of the genus Cotesia, Diadegma, Diadromus and Oomyzus. These wasps are also known from Africa and some are reported to effect excellent control of the diamondback moth elsewhere. 

Unfortunately, the locally existing wasps do not provide satisfactory control of the diamondback moth in eastern and southern Africa. For this reason, two species of wasps (Diadegma semiclausum and Cotesia plutellae) were imported and released by ICIPE in Kenya, Uganda and Tanzania. The former has provided almost complete control of this pest in highland growing conditions while the second is specific to mid-altitude, semi-arid areas where it also provides good control. 

Diamondback moth parasitoid (Diadegma semiclausum). This parasitic wasp was introduced and is now established in East Africa highlands.
(c) A. M. Varela, icipe
Diamondback moth parasitoid (Cotesia plutellae )
    (c) A. M. Varela, icipe
Coccon of the parasitic wasp Diadegma semiclausum. The wasp larva spins a brown, rounded cocoon within the silk cocoon of diamondback moth.
(c) A. M. Varela, icipe

It is important to distinguish parasitised diamondback moth caterpillars from healthy ones. Caterpillars parasitised by Diadegma semiclausum can be distinguished at the pupal stage. The larva of this parasitic wasp eats the diamondback moth caterpillar from inside and pupates inside the diamondback moth cocoon. The pupa of the parasitic wasps appears as a round elongated brown capsule within the diamondback moth cocoon. In contrast, it is possible to see the developing moth through the cocoon of a healthy pupa. 

The larva of Cotesia plutellae feeds inside the diamondback moth caterpillar and emerges from the caterpillar to pupate in a silky cocoon on the leaves near the dead diamondback moth caterpillar.

Diamondback moth pupal colour changes to brown before adult emergence. The developing moth can be seen through the cocoon. The pupa is 5 to 6 mm long.
(c) A. M. Varela, icipe
Diamondback moth caterpillar parasitised by Cotesia plutella. Note silky cocoon of the parasitoid near dead DBM caterpillar. The wasp larva emerges from the caterpillar and spins a white cocoon from which the adult wasp emerges.
(c) A. M. Varela, icipe

Pathogens including fungi, bacteria and viruses are naturally found causing diseases to the diamondback moth in the field. However, they generally occur during rainy seasons when problems with this pest are not very pronounced. There are some commercially available pesticides based on disease-causing microorganisms (microbiological pesticides). A well-known example is Bacillus thuringiensis (Bt). 

8. Biopesticides and physical methods

Bt (Bacillus thuringiensis)

Bacillus thuringiensis var. aizawai and Bt var. kurstaki are very effective in controlling infestations of the diamondback moth. Bt var. kurstaki is widely used at a weekly interval and a rate of 0.5/ha. This type of strategy provides effective control of this pest. However, continuous use of Bt can induce development of resistance. Bt kills the diamond back moth and does not harm beneficial insects. Bt insecticides should be applied when the newly hatch caterpillars appear. Sprays may need to be applied at intervals of 5 to 7 days when populations are high. Because Bt insecticides are UV-degraded treat crops in the late afternoon. 

Farmers experience

Farmers in some countries produce their own homemade biopesticides by collecting diseased diamondback moth caterpillars (fat and white or yellowish or with fluffy mould on them), crushing them and mixing them with water in a blender. Large tissue clumps are filtered out and the liquid is sprayed onto the crop (Dobson et al, 2002).

Neem (Azadirachta indica)
Neem-based products give a good control of the diamondback moth and are relatively harmless to natural enemies and non-toxic to warm-blooded animals. Since the action of neem is relatively slow, caterpillars may survive for a few days after application, but their growth and feeding is inhibited and they do not cause further damage to the crop. 

9. Information Source Links

  • CABI. (2004). Crop Protection Compendium, 2004 Edition. (c) CAB International Publishing.Wallingford, UK.www.cabi.org
  • Cornell International Institute for Food, Agriculture and Development. Global Crop Pests. Rueda and Shelton. Diamondback moth (DBM).www.nysaes.cornell.edu
  • Foster R. and Flood, B. (1995). Vegetable insect management with emphasis on the Midwest. Purdue Research Foundation. Meister Publishing Company, Willoughby, Ohio. ISBN: 0-931682-52-2.
  • HDRA (2000). Diamondback moth, Plutella xylostella. Pest Control No. TPC3. Tropical Advisory Service, HDRA,UK. www.gardenorganic.org.uk
  • ICIPE www.icipe.org
  • Natural Resources Institute, University of Greenwich, UK (2002): Integrated Vegetable Pest Management. Safe and sustainable protection of small-scale brassicas and tomatoes. By Hans Dobson, Jerry Cooper, Walter Manyangarirwa, Joshua Karuma and Wilfred Chiimba. ISBN: 0-85954-536-9.
  • Oisat. Organisation for Non-Chemical Pest Management in the Tropics. www.oisat.org
  • Rushtapakornchai, W., Vattanatangum, A. and Saito, T. (1992). Development and implementation of sticky trap for diamondback moth control in Thailand. In: Talekar NS, ed. Diamondback Moth and Other Crucifer Pests: Proceedings of the Second International Workshop. Shanhua, Taiwan: Asian Vegetable Research and Development Center, 523-528. www.avrdc.org
  • Shelton, A.M., Turner, A., Giga, D. Wilkinson, P., Zitzanza, E. and Utete, D. (1995). Diamondback moth. Zimbabwe Horticultural Crops Pest Management. NYSAES, Geneva NY. 2pp.
  • Talekar, N. S. and Shelton, A. M. (1993). Biology, Ecology and Management of Diamondback Moth. Annual Review of Entomology, Volume 38.http://web.entomology.cornell.edu
Last updated on:

Tue, 08/20/2019 – 10:23

Aphids

Credit:Biovision- Infonet

Groundnut aphid (A. craccivora) colony on cowpea. Apterae are 1.4-2.2 mm long. Alatae (winged form) 1.4-2.1 mm.
(c) James Litsinger. Reproduced from the Crop Protection Compendium, 2004 Edition. (c) CAB International, Wallingford, UK, 2004
Cotton aphid (Aphis gossypii) is a small aphid. Adults range from just under 1-1.5 mm in body length.
(c) Mississippi State University Archive, Mississippi State University, Bugwood.org
Green peach aphid (Myzus persicae) . Adult wingless females are 1.2-2.1 mm in body length and very variable in colour.
(c) Whitney Cranshaw, Colorado State University, Bugwood.org
Black bean aphids (A. fabae) colony (nymphs and alates) on leaf of runner bean (Phaseolus coccineus). Note the presence of an attendant ant (Lasius sp.) and, in centre of the picture, a hymenopteran parasitioid ovipositing into the aphids. A. fabae is a dark brownish to matt black aphid. Adults are often bigger than other Aphis spp. Apterae 1.5-3.1 mm, alatae 1.3-2.6 mm.
(c) Michael J. Amphlett. Reproduced from the Crop Protection Compendium, 2004 Edition. (c) CAB International, Wallingford, UK, 2004
Green peach aphids (Myzus persicae). Adult wingless females are oval-bodied, 1-2 mm in body length, of very variable colour
(c) Magnus Gammelgaard
Black bean aphids (Aphis fabae). Heavy attack of black aphids on a French bean plant. Their seize varies from 1.5 to 3.0 mm.
(c) A.M. Varela, icipe

Geographical Distribution in Africa

Geographical Distribution of Aphids in Africa (red marked) Updated on 11th July 2019. Source CABI.

2. General Information on Pest and Damage

Introduction

Major species of aphids attacking crops in Africa:

  • Banana aphid (Pentalonia nigronervosa)
  • Black bean aphid (Aphis fabae)
  • Cabbage aphid (Brevicoryne brassicae)
  • False cabbage aphid (Lipaphis erysimi)
  • Citrus aphid (Toxoptera citricidus, T. aurantii)
  • Green peach aphid (Myzus persicae)
  • Groundnut aphid (Aphis craccivora)
  • Cotton aphid (Aphis gossypii)
  • Russian wheat aphid (Diuraphis noxia)
  • Cypress aphid (Cinara cupressi)
  • Mango aphid (Toxoptera odinae)
  • Maize aphid (Ropalosiphum maidis)
  • Pea aphid (Acyrthosiphum pisum)
  • Sorghum aphid (Melanaphis sacchari)
Cotton aphid (Aphis gossypii) on flower
(c) A.M. Varela, icipe
Cotton aphid (Aphis gossypii) on the underside of a cotton plant.
(c) Courtesy EcoPort : Ronald Smith

Damage

Both adults and nymphs pierce plant tissues to feed on plant sap. Their feeding may cause rolling, twisting or bending of leaves. Heavily attacked leaves can turn yellow and eventually wilt. Aphids feeding on flower buds and fruits may cause malformed flowers and fruits. Aphids excrete a sugary, sticky liquid called honeydew that accumulates on leaves and branches. Sooty moulds (a fungal growth) grow on honeydew deposits turning leaves and branches black. Heavy coating with honeydew and sooty moulds may reduce photosynthesis, affecting plant growth and yield. 

Honeydew is a favourite food of some ant species. Thus, black ants are commonly found on plants with aphid infestations. These ants protect the aphids from natural enemies and are therefore considered indirect pests. Ants may even transport aphids from plant to plant. Many species of aphids have been implicated as major vectors of plant viral diseases. 

Affected plant stages 

Seedling stage, vegetative growing stage flowering stage and generative stage.

Affected plant parts 

Growing points, stems, leaves, inflorescences, fruits and whole plant.

Symptoms on affected plant parts 

Curled leaves, abortion of flowers, stunted growth and dieback. Sooty black mould becomes evident in heavy infestations. Black ants are very common in plant with aphid infestations. However, sooty moulds and ants are also associated with other honeydew-producing insects such as mealybugs, scales and whiteflies.

3. Biology and Ecology of Aphids

Eggs are very tiny, shiny-black, and are found in the crevices of bud, stems, and barks of the plant. Aphids usually do not lay eggs in warm parts of the world.

Nymphs (immature stages) are young aphids, they look like the wingless adults but are smaller. They become adults within 7 to 10 days. 

Adults are small, 1 to 4 mm long, soft-bodied insects with two long antenna that resemble horns. Most aphids have two short cornicles (horns) towards the rear of the body. The mouthparts are needle-sharp, resembling tiny straws. Their body colour varies from black, green, red, yellow, pink, white, brown, greyish, or purple. Adults of the same species may be wingless or winged (with two pair of wings). Winged aphids are usually dark in colour. Wingless forms are the most common; winged aphids are produced when they need to migrate, for example under overcrowded conditions with limited food source or when environmental conditions are unfavourable. 

Aphids lifecycle

Aphids have complicated life cycles. Females can reproduce with or without mating. Female aphids may lay eggs or give birth to wingless offspring, known as nymphs. In the warm parts of the world, as in the tropics, no male aphids are produced and female aphids do not lay eggs but give birth to small nymphs. A female can produce from 20 to over 100 nymphs. Young aphids grow quickly, becoming adult in about one week and start to reproduce. Thus the numbers increase rapidly under favourable conditions. Aphids live in clusters (known as colonies) on leaves and stems. Initially they are present on tender parts of the plant (young shoots and leaves), but as their number increases they can cover the whole plant. As the colony grows winged aphids are produced which fly away looking for new plants to start a new colony. 

Warm and dry weather is particularly favourable for rapid increase of aphid numbers.

4. Pest and Disease Management

Pest and disease Management: General illustration of the concept of infonet-biovision

This illustration shows the methods promoted on infonet-biovision. The methods shown at the top have a long-term effect, while methods shown at the bottom have a short-term effect. In organic farming systems, methods with a long-term effect are the basis of crop production and should be of preference. On the other hand methods with a short-term effect should be used in emergencies only. On infonet we do not promote synthetic pesticides. 

Further below you find concrete preventive and curative methods against Aphids.

5. Cultural practices

Monitoring

It is particularly important to scout crops during the critical periods of seedling and shoot growth and during flowering and fruiting. To monitor aphid populations, examine the undersides of the leaves and the bud areas for groups or colonies of aphids. Presence of ants may indicate presence of aphids. Early detection of aphids is important as they can multiply rapidly. Therefore, the crop should be scouted regularly. Yellow traps are useful for monitoring the arrival of winged aphids to the crop. The presence and abundance of natural enemies should also be recorded. For more information on monitoring traps click here. 

Economic Threshold Levels

Economic threshold levels have been developed for some few aphid species. One example is the threshold level for cotton aphid (A. gossypii) on cotton in Sudan: if 30% of the plants are infested during the first 2 months of the season, treatments are recommended (Stam et al., 1994). However, damage thresholds depend on many factors (crop stages, crop age, economic and climatic conditions). 

Instead of trying to use threshold levels, the growth of the aphid population within 3 to 5 days should be monitored. If a rapid growth of the number of aphids per plant is observed, and no or only few predators (e.g. ladybird beetles, lacewings) are present, treatments should be planned. Most plants can tolerate moderate numbers of aphids without great damage. However, even small numbers may need to be controlled in cases where aphids transmit virus diseases. Prompt control is necessary when numbers build-up and natural control is not satisfactory. 

Field sanitation and management

Grow healthy plants. Healthy plants are able to protect themselves better from pests and diseases than weak plants. Growers are strongly recommended to use compost in preference to manures, including liquid manures. Excess use of manures and mineral (artificial) fertilisers, particularly nitrogenous fertilisers, produces fleshy plant tissue attractive to aphids. Therefore their use should be avoided as far as possible.

Practice crop rotation. This may help to reduce aphid infestations, particularly of aphid species that are host specific (they feed and develop only on one or few plant species). 

Grow crops in mixed cropping. This involves plant diversity by growing diverse plants on the same land and at the same time. Common mixed cropping includes use of companion planting and intercropping. The mixture of plants needs to be carefully chosen. For instance, intercropping poses a problem when the minor crop harbours a disease or pest of the primary crop. Mixed cropping is in general beneficial to natural enemies, since it provides food and shelter. Depending on the plants used and the pattern of cropping, mixed cropping may help disrupt the lifecycle of pests and maintain their population below the economic threshold level. An example of a good intercrop in cabbage production is onions.

Use trap crops: some crops are particularly attractive to pests and can be used to trap them and protect the main crop. Monitoring of the trap crops is very important. They should be destroyed when they become severely infested, and before they are killed by the pest, or have completed their lifecycle, as the pest may move from the trap plants to the main crop. They can be removed and buried. Trap crops can be planted around the field to be protected, or interspersed among the rows.

Farmer experiences

Following are some examples of crop mixtures that are reported to help on managing aphid infestations: 

  • Trap crops such as dill, nasturtiums, and timothy grass near the main crop are reported to avoid aphid infestations in the main crop (The Bug Lady, 2004).
  • Anise, chives, garlic, onions, radish, and parsley are reported as good companion crops (Elwell and Maas, 1995; KIOF). Onion, chives, garlic and Mexican marigold repel aphids. The Kenya Institute of Organic Farming (KIOF) recommends leaving a few plants of Mexican marigold between the crops.
  • Intercropping beans with maize is a common practice in East Africa. It has been shown that infestations of black bean aphid in common beans were greatly reduced when intercropped with older and taller maize plants in a study in Kenya (Ogenga-Latigo et al., 1993).
  • Numbers of the aphid Aphis gossypii decreased in potatoes that were intercropped with onions (Allium cepa or Allium sativum). To achieve this reduction, the onions had to be planted within 0.75 m of potato plants (Potts MJ, Gunadi N, 1991).

6. Biological pest control

Natural Enemies

The most important aphid predators are predatory bugs (e.g. Anthocoridae, Miridae, Nabidae), carabid beetles (Carabidae), soldier beetles (Cantharidae),predatory gall midges(Cecidomyiidae), lacewings (Chrysopidae), ladybird beetles (Coccinellidae) and hoverflies (Syrphidae). 

In addition, parasitic wasps (parasitoids) are often involved in the control of aphid populations. Parasitised aphids can be easily recognised. They turn brown and hard and remain stuck to the plant surface. They are known as “mummies”. 

Depending on climatic conditions and crops fungi that cause diseases of insect pests (entomopathogenic fungi) can contribute to a rapid decline of aphid populations. Natural aphid enemies usually appear with a certain delay because they react to the presence of aphids.

It is important to help natural enemies to establish and improve their effectiveness (conservation biocontrol). This can be done through: 

  • Habitat management. For instance, leaving or growing flowering plants at the boarder of the crops or as companion plants within the crops attracts beneficial insects.
  • Avoiding use of pesticides toxic to natural enemies. If pesticides must be used, selective biopesticides that target specific pests should be preferred to broad-spectrum pesticides (that kill a wide range of insects including natural enemies)

Controlling ants feeding on honeydew produced by aphids. They disturb natural enemies giving protection to the aphids. Ploughing and flooding the field destroy ant colonies and expose eggs and larvae to predators and sunlight (Elwell and Maas, 1995).

Carabid beetle (Agonum dorsale) (6 to 8 mm long). An important predator of many aphid pests and the eggs of several dipterous (fly) pests.
(c) D.A. Kendall
Ladybird beetle larva of C. sexmaculatafeeding on aphids.
(c) Merle Shepard/Coastal Research and Education Center, Charleston, USA
Hover fly larva
(c) R.J. Reynolds Tobacco Company, Bugwood.org
Ladybird beetle (Coccinellidae sexmaculata) adult feeding on aphids. The adults are pink and black.
(c) M. Shepard / Coastal Research Center Charleston
Brown lacewing (Micromus timidus)
Hover fly adult
(c) Jonny N.Dell, retired, Courtesy of Bugwood.org

7. Biopesticides and physical methods

Neem

Neem extracts can control early infestations of some aphids, but they are not efficient against all aphid species. For a reliable and satisfactory control neem extracts must be applied at an early stage of aphid attack. Usually repeated spot sprays of affected plants are necessary to achieve control. Neem has a slow mode of action, and usually effects are not visible before 10 days after application. Some neem extracts (e.g. oil extracts) may be phytotoxic. Therefore, test the extract on few plants before going into full scale spraying. 

Neem products have in general no or low negative effect on natural enemies. However, products based on neem oil have stronger effects on some natural enemies.

Botanicals

Other botanical sprays reported to be effective against aphids include:

Chilli pepper 

Cut half a kg of hot chilli peppers in small pieces and boil them in 4 litres of water for 20 minutes. Add equal amount of soapy (bar soap) water, cool and spray (KIOF). or 
Pulverise 100g chillies in a mortar, shake vigorously with 1 litre of water and filter through a cloth. Dilute 1 part of this mixture with 5 parts of soapy water before spraying (G. Stoll, 1988). 
Chilli also repels ants.

Castor oil plant: 

As a general spray soak green leaves and seeds in water for 24 hours, filter and spray (Elwell and Maas, 1995).

Pyrethrum: 

Commercially available pyrethrum sprays are effective against aphid infestations, but also kill predators. It is therefore recommended to inspect plants regularly and control early outbreaks, before the insect becomes a big problem. Use spot sprays on infected plants.

Traps

Yellow sticky traps and yellow water traps are mainly used to monitor winged aphids. As the yellow colour attracts many insect species, including beneficial insects, use these traps only where necessary. 

Water traps 

Half-filled yellow pans or basins with soapy water are placed close to the plant but exposed enough so that aphids are attracted by the yellow colour. Water traps are mainly used to monitor winged aphids. As the yellow colour attracts many insect species, including beneficial insects, use water traps only where necessary.

Sticky board traps 

To make your own sticky trap, spread petroleum jelly or used motor oil on yellow painted plywood, 6 cm x 15 cm in size and up. Place traps near the plants but far apart enough to avoid leaves sticking to the board. Sticky yellow traps are mainly used to monitor winged aphids. As the yellow colour attracts many insect species, including beneficial insects, use water traps only where necessary.

Soap (fatty acids) spray

Spray with insecticidal soaps or with a soap and water solution. This control aphids and does not seriously affect natural enemies. 

  • Mix 1 tablespoon of dishwashing soap or 3 tablespoons soap flakes (non detergent) with 4 litres of water.
  • Add soap to water. Use mild soap or potash-based soap.
  • Start with a lower concentration and make adjustments of the strength after testing on few infested plants.
  • Always try on few infested plants before going into full scale spraying. Soaps can cause burning of leaves (phytotoxicity) on sensitive plants, like brassicas and certain ornamentals. Make 2 or 3 treatments in a 3 to 4 days interval for a better efficacy.
  • Apply on the infested plants thoroughly, including the undersides of the leaves. Spray early in the morning or late afternoon to avoid phytotoxic effects on crops.

Precaution:
Soap spray may injure foliage. Test these sprays on few leaves before applying to the entire plant. It may take 2 days for damage symptoms to appear.

Others

Ash

Ash can be used to effectively control aphids in vegetables. Ash should be dusted evenly onto infested parts of vegetables. Also aphids can be controlled by spraying wood ash mixed with soapy water and or lime (Elwell and Maas, 1995).

8. Information Source Links

  • Aphids. www.ent.uga.edu
  • Blackman, R. L. and Eastop, V. F. (2000). Aphids on the world’s crops. An identification and information guide. John Wiley & Sons, Ltd. ISBN 0 471 85191 4
  • CABI. (2004): Crop Protection Compendium, 2004 Edition. (c) CAB International Publishing. Wallingford, UK. www.cabi.org
  • Digital diagnostics. Database of Insects and Plant Diseases. Oklahoma State University. entoplp.okstate.edu
  • Gabriele Stoll: Natural Crop protection on the tropics. AGRECOL 1988. c/o OKOZENTRUM, CH-4438 Langenbruck, Switzerland.
  • Gordon’s aphid page. www.earthlife.net
  • Henry Elwell & Anita Maas: Natural Pest & Disease Control. Natural Farming Network, Zimbabwe, P.O.Box 301, Causeway, Harare 1995. ISBN: 0-7974-1429-0
  • KIOF – Kenya Institute of Organic Farming, Nairobi.
  • Ogenga-Latigo MW, Baliddawa CW, Ampofo JKO, 1993. Factors influencing the incidence of the black bean aphid, Aphis fabae Scop., on common beans intercropped with maize. African Crop Science Journal, 1(1):49-58.
  • Potts MJ, Gunadi N, 1991. The influence of intercropping with Allium on some insect populations in potato (Solanum tuberosum). Annals of Applied Biology, 119(1):207-213.
  • Stam PA, Abdelrahman AA, Munir B, 1994. Comparisons of control action thresholds for Heliothis armigera, Bemisia tabaci and Aphis gossypii on cotton in the Sudan Gezira and Rahad regions. Crop Protection, 13(7):503-512; 20 ref.
Last updated on:

Fri, 08/16/2019 – 15:38

Ch 2: Managing Whiteflies

Pest and Disease Management

Credits: Infonet

These illustration shows the methods promoted on infonet-biovision. The methods shown at the top have a long-term effect, while methods shown at the bottom have a short-term effect. In organic farming systems, methods with a long-term effect are the basis of crop production and should be used with preference. On the other hand methods with a short-term effect should be used in emergencies only. On infonet we do not promote synthethic pesticides. 

Further below you find concrete preventive and curative methods against Whiteflies.

Monitoring and decision making

For early detection inspect for adults and eggs. They are usually found on young leaves. Watch out for whiteflies flying up when the crop is disturbed. It is important to identify the whitefly and the type of damage caused, as well as the stage of the crop for making decision. Small numbers of whiteflies do not cause major direct plant damage to healthy, mature plants and therefore do not justify any chemical intervention. Control measures can be justified if large numbers of whiteflies are present during the early stages of the crop. However, where virus transmission is involved, as is the case of the tobacco whitefly on tomatoes, sweet potato or cassava, even small numbers of whiteflies may need to be controlled. 

Yellow sticky traps can be used to monitor the presence of whiteflies for timing of interventions. See more on section on traps below.

The following description helps to distinguish the most important whitefly species in Africa: However, for authoritative identification contact the Entomology Department of the National Museums of Kenya. 

Adult of the greenhouse whitefly
(c) M. Billah, A. M. Varela, icipe

Adults of the tobacco whitefly(B. tabaci) have wings all white in colour, and hold them tent-like over the body, giving a narrow, triangular, appearance while other whiteflies usually hold their wings flatter, which give them a flattened appearance. 
The larval stages and puparium of this whitefly are naked (not covered with waxy white material). They appear as pale yellow oval specks to the naked eye. On a closer look they are oval and flat with a rounded outside margin, tapering toward the leaf surface as viewed from the side. In contrast, the pupae of the greenhouse whitefly have distinctly ridged outside margins with flat, vertical surfaces surrounded by short threads. 

Adults and eggs of the cabbage whitefly (Aleyrodes proletella).
(c) A. M. Varela, icipe
Immature stages of the citrus woolly whitefly
(c) B. Loehr, icipe

The wings of the greenhouse whitefly (Trialeurodes vaporariorum) are completely white, while the cabbage whitefly (Aleyrodes proletella) has dark flecks on the wings.

Adults of the citrus woolly whitefly (Aleurothrixus floccosus) have wings all white in colour. Eggs are in a circle or half a circle. The immature stages are covered by abundant, dirty-looking, flocculent white wax, which gives them a woolly appearance. They usually form large dense colonies covered with cotton-like secretions on the lower leaf surface. 

Adult of the spiralling whitefly (Aleurodicus dispersus) are white, although pale or dark spots may occasionally occur on the forewings. Eggs are laid on the lower leaf surface in characteristic spiral patterns, resembling fingerprints of white material secreted by the female. Nymphs and adults produce considerable amount of white wax. When the adults move around they leave behind a trace of waxy material. They usually form dense colonies on the lower leaf surfaces.

Providing conditions for growing healthy plants

Ensure adequate growing conditions for the crop such as good soils, adequate water supply, proper feeding (avoid application of high doses of nitrogen fertiliser, since it favours development of the pest), proper spacing and good nursery management to start the crops with healthy, vigorous plants. If the plants are to be raised in a seedbed and later transplanted like many vegetables, keep the seedlings protected under a fine meshed insect netting until they are ready for transplanting. Make sure the netting is always properly closed. 

Mixed cropping systems

Selection of crops for intercropping can be used to manage whitefly populations. For instance, interplanting tomatoes with capsicum or cucumber has reduced whiteflies numbers when compared with tomatoes alone or tomatoes planted with eggplant or okra. 
Planting of border rows with coriander and fenugreek, which are non-host of B. tabaci, will serve as windbreaks, and are favourable for natural enemies and also repellent to whiteflies. 
Growing African marigolds and nasturtiums has been reported to discourage whiteflies. 

Planting date

Avoid the season when whiteflies are more likely to occur. 

Host plant 

Growing resistant varieties is particularly useful for the management of diseases caused by viruses transmitted by whiteflies, in particular, B. tabaci. Outbreaks of African cassava mosaic virus (CMV) in East Africa are associated with the varieties grown and are less devastating in areas where many different varieties are grown. The outbreak of ACMV in East Africa has been contained by farmers adopting resistant varieties introduced from Nigeria (IITA) or those selected by the National Agricultural Research Organisations from the available local varieties. Resistant varieties introduced from Nigeria include “SSA”,” Nase 1″, “Nase 2”, and “Nase 3” (Migyera) (OFDA-CMD Project). 

Tomato varieties resistant to TYLC virus are also available from AVRDC and can be bought in Tanzania and Kenya. For instance the varieties “Fiona” and “Tyking” are resistant to TYLCV in Tanzania. For more information on tomato yellow leaf curl virus (TYLCV)
 Sanitation

Weeds play an important role in harbouring whiteflies between crop plantings. They also often harbour whitefly-transmitted viruses. Therefore, weeds should be removed in advance of planting. Fields should also be kept weed free.

Biological pest control

Natural enemies

Whiteflies are attacked by a large number of natural enemies: parasitic wasps (e.g. Eretmocerus spp., Encarsia spp.), predatory mites (Amblyseius spp. and Typhlodromus spp.), predatory thrips, lacewings, rove beetles and ladybird beetles. The dusty lacewing Conwentzia africana is considered to be one of the most important predators of B. tabaci in East and southern Africa (Legg, 2003). 

Parasitised pupae can be recognised by the black colour of the puparium, and later, when the parasitic wasp has emerged, by an irregular round hole on the puparium, which is chewed by the emerging wasp. Parasitic wasps are very important for control of whiteflies. Encarsia formosa in particular, has been widely used for control of whiteflies worldwide. 

Two parasitic wasps Encarsia guadaloupe and Encarsia haitiensis have provided control of the spiralling whitefly an introduced pest in West Africa (Neuenschwander, 1998; James, et al, 2000). 

The citrus woolly whitefly, accidentally introduced into East Africa, is now under control by the parasitic wasp Cales noacki, introduced and released in the region in the late 90s.

Several fungi (e.g. Verticillium lecanii, Beauveria bassiana, Paecilomyces fumosoroseus) attack whiteflies and can be useful control agents in situations where the crop is grown in high humidity conditions. Commercial preparations are available. 

Natural enemies commercially available in Kenya include the parasitic wasp Encarsia formosa, produced by Dudutech and registered as Encartech(r), and the pathogen Beauveria bassiana sold under the trade name Bb plus(r) by Juanco SPS Ltd. 

Mortality of whiteflies by natural enemies is particularly important in crops where feeding damage is the cause of losses, rather than virus transmission. In cases where the whiteflies are vectors of virus diseases, control provided by natural enemies is generally not sufficient to prevent virus spread and transmission.

Biopesticides and physical methods

Neem (Azadirachta indica)

Neem-based pesticides are reported to control young nymphs, inhibit growth and development of older nymphs, and reduce egg laying by adult whiteflies. They also reduce significantly the risk of Tomato Yellow Leaf Curl Virus transmission. Efficacy of neem-based pesticides can be enhanced by adding 0.1 to 0.5% of soft soap. 
 Physical methods

Yellow sticky traps usually used to monitor the presence of whiteflies for timing of interventions, have also been used as a control method for low density infestations in enclosed environments.

  • Yellow plastic gallon containers mounted upside down on sticks coated with transparent automobile grease or used motor oil. These should be placed in and around the field at about 10 cm above the foliage. Clean and re-oil when traps are covered with flies.
  • Yellow sticky boards. To use, place 1 to 4 yellow sticky cards per 300 square metre field area. Replace traps at least once a week. It is difficult to determine the population of newly trapped whiteflies on a sticky card from the previously trapped ones. To make your own sticky trap, spread petroleum jelly or used motor oil on yellow painted plywood, 6 cm x 15 cm in size. Place traps near the plants but faraway enough to prevent the leaves from sticking to the board. Traps when hung should be positioned 60-70 cm above the plants.
  • Yellow plastic trapping sheets. A 2 m long x 75 cm wide yellow plastic sheet coated with motor oil, both ends attached to bamboo or wooden poles and carried by 2 persons through the field to mass capture adult flies
  • Yellow plastic drinking cups coated with adhesives and stapled on stakes above plant canopies to trap flies

Flour/Starch preparation has been listed by several authors as successful against whiteflies. Ensure the spray reaches the underside of the leaves, where the whiteflies like to hide. 

Plastic covers and mulches. Preventing physical contact of the whiteflies with the plant can prevent the transmission of virus diseases. This can be done by using plastic covers and mulches and by cultural methods. Several cover crops (forage, peanut, weeds) and inert covers (silver, yellow, and white/black plastic mulches) have been shown to reduce whitefly damage in tomatoes. However, when using plastic covers, care should be taken to avoid sunscald.
This is effective as long as the plants are young and do not cover the mulch. The whiteflies will be more attracted by the colour of the plastic mulch. The heat of the plastic kills the whiteflies. The protection can last for 10 to 20 days after transplanting and about 30 days after direct seeding.

Covering tomato seedling nurseries with nylon nets or use of tunnels for 3 to 5 weeks protects seedlings from whiteflies infestation. These methods have been reported to reduce the transmission of the Tomato Yellow Leaf Curl Virus in several countries.

Spraying with soap and water reportedly controls whiteflies. However, care should be taken, since the use of strong soaps, or soft soaps at high concentrations can scorch the plants.

Information Source Links

  • CABI. (2005). Crop Protection Compendium, 2005 Edition. CAB International Publishing. Wallingford, UK. www.cabi.org
  • Legg, J., Gerling, D., Neuenschwander, P. (2003). Biological Control of Whiteflies in Sub-Saharan Africa. In Biological Control in IPM System in Africa. CAB International. ISBN: 0-85199-639-6.
  • Mound, L.A. and Halsey, S.H. (1978). Whitefly of the World. British Natural History Museum.. ISBN: 0-471-99634-3.
  • Tropical Whitefly IPM Project: Book ‘Whitefly and Whitefly-Borne Viruses in the Tropics: Building a Knowledge Base for Global Action’. www.researchgate.net
  • United States Department of Agriculture, Whitefly Knowledgebase: www.entnemdept.ufl.edu
Last updated on:

Tue, 08/20/2019 – 10:00

Ch 1: Whiteflies

Whiteflies

Credit:Biovision-Infonet

The tobacco whitefly ( Bemisia tabaci) adult (bottom right) about 1 mm long, beside two Trialeurodes vaporariorum adults.
(c) Ian D. Bedford. Reproduced from Crop Protection Compendium, 2004 Edition. (c) CAB International Publishing. Wallingford, UK.

Scientific Name: 

Aleurodicus disperses, Aleurothrixus floccosus, Aleyrodes proletella, Bemisia tabaci, Trialeurodes vaporariorumOrder / Family: 

Homoptera: AleyrodidaeType of

Pest: Insect

Host Plants: Beans, Cabbage/Kale, Brassicas, Cassava, Citrus plants, Cotton, Cucumber, Eggplant, Green gram, Mango, Okra, Papaya, Peppers, Pigeon pea, Pumpkin, Sesame, Sweet potato, Tomato, Watermelon

1. Geographical Distribution in Africa

Geographical Distribution of Whiteflies in Africa (red marked). Updated on 9 July 2019. Source CABI 

2. General Information on Pest and Damage

Damage

Tomato plant infected with Tomato Yellow Leaf Curl. Note upward and inward rolling of the leaf margins.
 (c) Ian D. Bedford. Reproduced from the Crop Protection Compendium, 2005 Edition. CAB International Publishing, Wallingford.

Whiteflies cause direct damage to plants by sucking plant sap and removing plant nutrients, thereby weakening the plants. Damage may be more severe when plants are under water stress. In addition, they often produce large quantity of honeydew that leads to the growth of sooty mould on the lower leaves, blocking or reducing the photosynthetic capacity of the plants. The honeydew also contaminates the marketable part of the plant, reducing its market value or making it outright unsaleable. Infested plants may wilt; turn yellow in colour, become stunted or die when whitefly infestations are severe or of long duration. 

Whiteflies are also serious indirect pests as vectors of virus diseases. Bemisia tabaci transmits serious virus diseases on cassava, cotton, tobacco, tomato, beans, chillies, and sweet potatoes. Whitefly transmitted viruses are among the most serious virus diseases on plants; Virus infection often results in total crop losses. This whitefly is the vector of a range of leaf curl disease-inducing virus, in Eastern and Southern Africa, including Tomato Yellow Leaf Curl Virus, the African Cassava Mosaic Virus, Cowpea Mild Mottle Virus, Watermelon Chlorotic Stunt Virus among others.

The African Cassava Mosaic Virus is one of the most important factors limiting cassava production in Africa. In sweet potatoes B. tabaci transmits the Sweet potato Chlorotic Stunt virus, which together with the aphid-transmitted Sweet potato Feathery Mottle Virus causes the Sweet potato virus Disease, the most important disease constraint to sweet potato production in Sub-Saharan Africa (Legg et al., 2003).

Major species of whiteflies in Africa:

  • The greenhouse whitefly (Trialeurodes vaporariorum)
  • The tobacco whitefly or sweet potato whitefly (Bemisia tabaci)
  • The spiralling whitefly (Aleurodicus dispersus)
  • The citrus woolly whitefly (Aleurothrixus floccosus)
  • The cabbage whitefly (Aleyrodes proletella)

Host range

The tobacco whitefly (Bemisia tabaci) and the greenhouse whitefly (Trialeurodes vaporariorum) attack a very wide range of wild and cultivated plants. Bemisia tabaci is the dominating whitefly in the region. Its host range includes cotton, tobacco, vegetables (tomatoes, eggplant, okra, bell peppers, cucurbits, etc.), legumes (beans, soybeans, cowpeas and groundnut), tuber and root crops (sweet potato, cassava, potato) among others. The host range of Trialeurodes vaporariourm is similar to the one for Bemisia tabaci, but the former usually occurs at higher altitudes and cooler climates than B.tabaci. Trialeurodes vaporariorum attacks many plants grown under protected conditions (greenhouses) in temperate countries, the most severely affected crops are aubergine, cucumber, beans, sweet peppers, tomatoes and a large number of ornamentals. The status of this whitefly in field grown crops in the region is not clear. 

The cabbage whitefly (Aleyrodes proletella) is a pest of Brassicas but rarely reaches levels that require intervention. 

The citrus woolly whitefly (Aleurothrixus floccosus) is found mainly on citrus plants, but also attacks coffee (arabica), guava, eggplant, aubergine, mango, and several wild plants. 

The spiralling whitefly (Aleurodicus dispersus) feed on many plants. In West Africa, it has been observed causing damage on many food crops, including cassava, soybean, pigeon pea, citrus, papaya and others. This whitefly has also been recently found in East Africa. 
 Symptoms

Feeding of whiteflies causes yellowing of infested leaves. Whiteflies excrete honeydew, a clear, sugary liquid. This honeydew covers the lower leaves and supports the growth of black sooty mould, which may coat the entire plant. Where plant viruses are transmitted plants show the typical symptoms of the virus diseases. Presence of whiteflies can also be recognised by a cloud of tiny whiteflies flying up when the plants are shaken. The whiteflies resettle soon on the plants. 

Affected plant stages

Seedling, vegetative growing and flowering stage 

Affected plant parts

Leaves. 

Symptoms by affected plant part

Leaves: honeydew or sooty mould.

3. Biology and Ecology of Whiteflies

Eggs of spiralling whitefly
(c) A.M.Varela, icipe

Eggs are tiny (about 0.2 mm long) and pear-shaped. They stand upright on the leaves, being anchored at the broad end by a short stalk inserted into the leaf. They are laid usually in arcs or circles, on the undersides of young leaves. Eggs are whitish in colour when first laid, but gradually turn brown. Some whiteflies deposit large quantity of wax around the eggs in the form of a loose spiral like a fingerprint. Hatching occurs after 5 to 10 days at 30degC depending on species, temperature and humidity.

On hatching, the first instar or crawler is flat, oval, very small (barely visible even with a hand lens) greenish-white in colour. It is the only mobile immature stage. It moves to a suitable feeding location on the lower leaf surface where it settles. It moults, loosing the legs and antennae, and cannot move throughout the remaining immature stages. They pass through two additional feeding stages, known as nymphs. The nymphs are usually oval or oval-elongate in shape, and are simple in appearance like small scale insects. Nymphs of many species produce waxy secretions around the margins and the dorsal surface of their body. 

The last (fourth) immature stage is known as puparium. In this stage the metamorphosis to adult occurs. The red eyes of the adult developing inside are visible through the skin (integument). As the other larval instars it is greenish in colour and is scale-like, but becomes more bulky shortly before the adult emerge. They are usually found on mature leaves. The adult emerges about 6 days after pupation. It usually emerges through a T-shaped split in the dorsal surface of the pupal case.

The total nymphal (immature) period last 2 to 4 weeks depending to temperature. Large populations may develop within 3 weeks under optimum conditions, and the lower leaf surfaces may be almost covered by immature stages. 

Tobacco whitefly Bemisia tabaci adult (bottom right) about 1 mm long, beside two Trialeurodes vaporariorum adults.
(c) Ian D. Bedford. Reproduced from Crop Protection Compendium, 2004 Edition. (c) CAB International Publishing. Wallingford, UK.

Adults are small (1 to 3 mm long), with two pairs of wings that are held roof-like over the body. They resemble very small moths. Their body is pale yellow. The body and wings are covered with a powdery, waxy coating. Whiteflies are mostly white, but can also be yellowish and some species have dark or mottled wings. They have sucking mouthparts. They are often found clustered in groups on the underside of young leaves and readily fly away when disturbed. A female may live for 60 days; life of the male is generally much shorter (9 to 17 days). 

Means of movement and dispersal

Whiteflies adults do not fly very efficiently, but once airborne can be transported long distances by the wind. All stages of the pest, but particularly the immature stages (which are small and easily overlooked) are likely to be carried on plant materials.

Whitefly life stages
(c) A.M. Varela, icipe