CH 3. What is Agroforestry?

What is Agroforestry?

Credit: Biovision-Infonet

Sorghum grown under Faidherbia albida and Borassus akeassii near Banfora, Burkina Faso
(c) Marco Schmidt (Source: Wikipedia)
Trees along borders of fields
(c) B.T. Kang, IITA (1996)

1. Introduction

Agroforestry is an old practice, consisting of growing perennial trees and shrubs in association with agricultural crops, pastures and/or keeping livestock in the same field. Agroforestry aims to use agro-biodiversity in generating multiple services. Trees and shrubs provide mulching material, green manure, animal fodder, soil erosion control, shade, nutrient cycling and improved soil fertility and also socioeconomic benefits e.g. saleable products such as fruits, fuel wood and charcoal, timber for construction, craft materials, etc.

The classification of the different types of agroforestry is based on the type of environment and on the combination of the components. In the humid lowland tropics, the broadest range of homegardens and multi-level cropping are found, whereas agro-silvopastoral systems dominate in semi-arid and subhumid zones. In tropical highlands vegetation strips are common, in order to reduce erosion risk. 

Basically, there are three categories of agroforestry systems:

  • Agrosilvicultural systems: Trees with crops e.g. taungya and alley cropping
  • Silvopastoral systems: Trees with livestock/pasture e.g. trees and shrubs on pastures and multipurpose trees, fodder trees and shrubs grown on or around cropland
  • Agrosilvopastoral systems: Trees with both crops and livestock e.g. compound farming.

Next to climatic conditions and soil type, success of agroforestry depends on the right choice of species combination, management practices and the understanding and motivation for using it. An agroforestry system involves two or more plant species and/or animals (including at least one woody perennial), it has more than two outputs and has a cycle of more than one year. 

Distribution of the plant components can vary in space and time. Plant components can be mixed in different densities (see images below) and have a separate long/short cropping/fallow cycle. 

Trees along borders of fields.
(c) B.T. Kang, IITA (1996)
Alternative rows of plant components.
(c) B.T. Kang, IITA (1996)
Alternative strips or alley cropping.
(c) B.T. Kang, IITA (1996)
Random mixture of plant components.
(c) B.T. Kang, IITA (1996)

2. Ecological Aspects of Agroforestry

Agroforestry systems have the following basic principles:

  • Competition between the plants must be minimised
    This can be achieved by planting the plants in such a way that they are not using resources all at the same time. For instance, acacia trees (Faidherbia albida) loose their leaves during the millet growing season, and are suitable to feed cattle, as their pods are rich of proteins. Therefore, many African farmers grow acacia trees combining with millet and cattle.
  • Complementarity among the plants must be maximised
    Complementarity and competition depend on the root system of the crops and trees/shrubs, i.e. on the depth or shallowness of the roots. If one has deep, the other one shallow roots, they will not compete for nutrients and water, but might complement/ benefit from each other.

(Sanchez 1995)

Agroforestry has following advantages:

  • Improvement of soil fertility. Trees provide mulch when their leaves, fruits and branches fall down and decompose. This results in an increase of organic matter and recycling of nutrients from deep in the soil, and leguminous trees fix nitrogen that can benefit food crops.
  • Effects on soil moisture and microclimate. Shading and windbreak effects of trees influence microclimate and help to conserve soil moisture. Shade helps reducing the soil temperature and the amount of water that evaporates into the air. Though their roots may also deprive crops of moisture.
  • Soil conservation. Trees can conserve the soil in many ways. They cushion the impact of raindrops on the soil and reduce the amount of rain-splash erosion. Their roots bind/stabilise the soil. Planted along contours, they can interrupt the flow of water running off the surface. They can act as windbreaks protecting the soil against wind erosion
  • Improvement of biodiversity. Agroforestry systems improve diversity and quantity of animals/wildlife by offering a greater variety of habitats

Drawbacks to agroforestry: 

One is labour is required. However, it can be reduced by proper planning. Rows of trees can be planted, weeded and guarded at the same time as the food crops. Surface mulching with leaves involves less labour than digging them in. Any digging needed can be done at the same time as the land is prepared for the crops.

Trees need to be watered and protected when young. Later on they can survive on rain water alone. 
Trees can also lower yields of maize and other food crops. However, if both crop and tree products are taken into account, a higher total yield from unit of land will be achieved than in a monoculture. Though a field of maize may produce a high yield, it is not sustainable in a long run as problems associated with pests and diseases and soil exhaustion will soon lead to decline in yields and higher production costs. 

Interactions in agrosylvicultural systems.
(c) B.T. Kang, IITA (1996) after Young (1998)
Silvopastoral system.
(c) B.T. Kang, IITA (1996)

3. Selection of Trees and Shrubs Species

The multipurpose trees

Following species were found to perform well, in terms of survival, growth, and wood and foliage production, across diverse agro-ecological zones:

  • Moringa oleifera
  • Senna siamea
  • Senna spectabilis
  • Acacia auriculiformis
  • Leucaena leucocephala (except in acidic soils)
  • Some provenances of Gliricidia sepium

Fodder trees

Fodder refers to the green parts of the tree, for example leaves or sometimes flowers and pods, eaten by browsing or grazing animals. Fodder trees include species of Acacia, Leucaena, Prosopis and many others. 
One of the best fodder trees is Calliandra, having high protein content. Calliandra grows up to 4 to 6 metres, requires rainfall above 1000 mm per year and grows well in well-drained soils. Nine months after planting, fodder can be harvested. Harvesting can be done 4 to 6 times per year. 

Criteria for selection of fodder species:

  • Edible to livestock and rich in protein
  • Easy to manage
  • Drought tolerant
  • Tolerant of trampling if to be grazed
  • Able to resprout easily

4. Taungya system (shamba system)

The Taungya system combines forestry crops and agricultural crops during the first years of establishment of the forestry plantation. The main objective of taungya is wood production. 
Generally, the land belongs to the forestry departments, who allow subsistence farmers to grow their crops for two or three years. Farmers have to take care of the forestry seedlings, getting in return part or all of the agricultural produce. 

The Taungya system comes originally from Myanmar (Burma) and means hill (Taung) cultivation (ya). In East Africa it is known as Shamba system.

5. Dispersed trees on cropland

The practice of growing trees in fields while crops are grown alongside or underneath can be done either by protecting and managing the trees that are already there or by planting new trees.

There are different spacing patterns and densities of placement depending on the type of tree chosen and of crop grown, but trees are generally planted at least 8-10 m apart.

Advantages:

  • Growing trees with crops can increase crop yields due to shading and the addition of nutrients and organic matter to the soil.
  • Trees can be a breeding place for beneficial insects and other creatures that can reduce crop pest numbers.
  • Trees can provide products of commercial and subsistence value.

Disadvantages:

  • Trees can attract birds and crop pests, which can damage crops.
  • Competition with crops for water, nutrients. It is important to plant trees with deeper roots than those of the crops grown alongside.

6. Compound farming (Home gardens)

Compound farming is also known as home garden, village-forage garden, kitchen garden and household garden. In Africa, they are known as:

  • Compound farms in Southeast Nigeria, humid lowlands
  • Chagga home gardens in Mt. Kilimanjaro, Northern Tanzania, highlands
  • Ka/Fuyo gardens in Hounde region in Burkina Faso, semi-arid to sub-humid lowlands

Compound farming consists on growing trees, shrubs, vines and herbaceous plants in or around the homesteads, aiming mostly food production for household consumption. In home gardens perennial crops and annual crops are grown side by side. Home gardens are characterised by the intensive use of multi-purpose trees, shrubs, food crops and animals. Typical is also the high species diversity and the complex, layered structure (3-4 vertical canopy layers). Near the ground there is a herbaceous layer consisting of plants such as beans, pulses, root crops grasses and medicinal plants, which grow to about 1.5 metres. The middle layer (1-3 m height) consists of small trees that tolerate some amount of shade such as coffee, tea, banana, papaya or food plants such as cassava, etc. The upper layers are usually about 20 metres high and consist of trees for fruit, fuel, timber, shade and fodder. 

Animals are also usually included in the system. 
The Chagga home gardens in Tanzania are based on Arabica coffee and banana for commercial purposes.

Advantages:

  • Production of food is continuous and diverse.
  • Farmers have easy access to food, timber, fuel, fodder, spices and medicines.
  • Home gardens protect the soil and conserve water.
  • Labour can be used efficiently because home gardens are situated close to houses.
  • Produce may be sold locally and act as a financial buffer in times of need.

Disadvantages:

  • The high diversity of plants in a home garden can provide a habitat for species that could become pests or introduce diseases.

7. Alley cropping

Alley cropping is also known as alley farming or hedgerow intercropping. It consists in growing food crops between hedgerows of shrubs and trees, specially leguminous species. The arrangement of the components is uniform (not mixed), consisting of strips with different widths. 
During growing of the crops, the hedges get pruned regularly, to avoid shading of the crops and to provide biomass, enhancing the nutrient status and physical properties of the soil. 

Alley cropping is developed to improve or maintain crop yields by improving soil fertility and micro-climate through the cycling of nutrients, mulching and weed control. This can be reached by using specific tree species that produce foliage and fix nitrogen, enriching the soil. By planting deep-rooted trees and shrubs that grow quickly in hedgerows, essential plant nutrients are recycled to the benefit of crops planted in alleys between the hedgerows. Furthermore, a good mixture of trees and shrubs can provide animal fodder, protection against soil erosion, shade and windbreaks, fuel wood and construction material. 

Alley cropping is mostly used in humid or subhumid tropical areas on fragile soils and seems to work best where farmers need to intensify crop production but have soil fertility problems.

The technique of alley cropping requires careful planning and management. It is preferable that the species used have a light open crown that lets sunlight pass through onto the crops that are being grown. It is also possible to prune species with a denser crown. The trees used must also be capable of rapid resprouting after coppicing.

Alley cropping management cycle

1. The trees are planted in lines and crop grown between the rows.
2. When the shade from the trees begins to interfere with the crops they are coppiced or pollarded.
3. The coppiced branches are placed between the rows. Leaves will fall to the ground adding organic matter to the soil when they breakdown. Branches and twigs can be gathered for fuel or other purposes.
4. Trees resprout.
5. The cycle is repeated.

Advantages of alley cropping:

  • Improvement of soil fertility and structure and micro-climate conditions, thereby benefiting crops.
  • A longer cropping period and higher land use intensity.
  • Trees used can provide products of commercial and subsistence value.

Disadvantages of alley cropping:

  • The technique will take some years to establish, so farmers will have to wait for the benefits.
  • Farmers may not have the capital available for the investment in trees.
  • Alley cropping requires considerable labour and management – results will be poor if planting and pruning schedules are not carried out properly.
  • Competition with crops for water and nutrients. It is important to plant trees with deeper roots than those of the crops grown alongside.

8. Improved Fallows

Fallows are defined as following:
1) Allowing crop land to lie idle, either tilled or untilled, during the whole or greater portion of a growing season. Tillage is usually practised to control weeds and encourage the storage of moisture in the soil.
2) Land rested from deliberate cropping, not necessarily without cultivation or grazing but without sowing.
3) State of land left without a crop or weed growth for extended period, often to accumulate moisture.

Improved fallow is the replacement or enhancement of natural fallow vegetation by the introduction of selected trees or shrubs. The purpose of improved fallow is to shorten the fallow period and/or increase the yield of subsequent crops. This is done by planting trees or shrubs which can help to restore nutrients to the soil and to suppress weeds as well as providing useful by-products. The trees therefore enrich the fallow both biologically and economically.

In this practice the cropping period usually alternates with the tree-growing period. However, it is possible to keep some trees during the cropping period and many farmers have combined the method of improved fallow with alley cropping.

By planting soil enriching species, the minimum fallow period can be shortened from 15 to 20 years to about 8 to 10 years. However in Kenya, Sesbania is grown in a 3 year rotation and Tephrosia in a 1 year rotation.

Advantages:

  • The time required for soil enrichment can be shortened; the tree canopy and fast growing species can suppress weeds.
  • Soil erosion is minimised.
  • The use of a wide variety of species can reduce pests, weeds and diseases.
  • This method is relatively inexpensive to establish and maintain.
  • The wood can be used or sold at the end of the fallow period.

Disadvantages:

  • The planting of seedlings and tree cutting must be done during the same period of crop planting – labour may be a limiting factor at this time.
  • The fallow will need protection from browsing animals.

9. Contour vegetation strips

Contour vegetation strips are living barriers of trees and shrubs which are planted along the contour lines of a slope, in order to control water and soil erosion. These lines of vegetation can also provide useful products such as food, fuel, building poles, fodder or gum.
There are many factors to consider when building contour strips as bad design can lead to even more severe erosion. The effectiveness of the vegetation strips depends on the type of trees planted, the spacing of the trees and the width of the strip, the steepness of the slope, the amount of rainfall and the soil type.

Advantages:

  • Strips can provide additional nutrients and organic matter into the soil. This can be increased by using nitrogen-fixing plants.
  • Excess vegetation can provide food for animals. These can be allowed to browse through the strip to feed on crop remains after harvesting.

Disadvantages:

  • Contour strips take up land which could be used for crops.

10. Planting on terraces

Terraces are normally used as soil and water conservation measures on slopes. They provide flat areas of land that can be planted with crops. 
Building terraces involves digging ditches and making ridges. Along the contours of a slope, grasses, trees and shrubs can be planted on the ridges, helping to stabilise the ground, providing leaf mulch, protecting crops from wind and providing other useful products such as food, fuel, building poles or fodder.

Trees can be planted on the ridge of the terrace or at the back of the terrace. If the tree is planted at back of the terrace it will get all of its water requirements. If a tree is planted on the ridge of the terrace, it will be on drier ground but the leaves will spread around more evenly and provide more nutrients for crops. Trees can be planted in both locations if the terrace is wide enough.
The type of tree or hedge used will depend on the site it is planted on and on the kind of products or services you wish it to provide. If the aim of the terrace is to stabilise the soil, trees and shrubs with strong roots systems should be planted. These will be able to withstand the movements of soil and water.

Advantages:

  • Stabilisation of the slope, which results in soil and water conservation and a better environment for crops to grow in.
  • Shelter from wind.
  • Pest control by providing a breeding place for beneficial insects.
  • Increased area of land that can be cropped.
  • Useful by-products such as food, fuel, building poles or fodder.

Disadvantages:

  • As the structure of the land is changed quite dramatically, land tenure rights may first need to be established or secured.
  • Building terraces require adequate skills and material, labour and capital and also the capacity to maintain the structures for years to come.

11. Information Source Links

  • Franzel, S. and Scherr, S.J. (eds) (2002). Trees on the farm. Assessing the Adoption Potential of Agroforestry Practices in Africa. ICRAF/CABI Publishing. ISBN 0 85199 561 6.
  • Garrity, D., Okono, A., Grayson, M. and Parrott, S. (eds.) (2006). World Agroforestry into the Future. Nairobi: World Agroforestry Centre.
  • HDRA (2001). Agroforestry in the tropics. HDRA – the organic organisation, UK. www.gardenorganic.org.uk
  • Huxley, P. and van Houten, H. (1997). Glossary for agroforestry. ICRAF Nairobi, Kenya. ISBN 929059 124 2
  • International Institute of Rural Reconstruction (IIRR). Sustainable Agriculture Extension Manual. Available at www.betuco.be/
  • Kang, B.T. (1996). Sustainable agroforestry systems for the tropics: concepts and examples. IITA Research Guide 26. www.iita.org
  • Robert, B., Caine, C, Cooper, D., Cousins, B., and Roberts, S. (1998). People’s Farming Workbook. Environmental and Development Agency. David Philip Publishers, South Africa. ISBN: 0 86486 431 0
  • Rocheleau, D., Weber, F. and Field-Juma, A. (1988). Agroforestry in dryland Africa. ICRAF, Nairobi, Kenya. ISBN 92 9059 049 1
  • Sanchez, P.A. (1995). Science in agroforestry. In: Agroforestry systems, Vol.30, Numbers 1-2, 5-55.
  • Schroth, G. and Sinclair, F.L. (Eds) (2003). Trees, Crops and Soil Fertility: Concepts and Research Methods. CAB International.
  • Young, A. (1990). Agroforestry for soil conservation. Nairobi: ICRAF. CAB International.

Fruit flies

Credit: Biovision-Infonet

Melon fly (Bactrocera cucurbitae)
(c) Courtesy EcoPort (http://www.ecoport.org): Scott Bauer
Natal fruit fly (Ceratitis rosa), wing length 4-6 mm.
(c) Courtesy EcoPort (http://www.ecoport.org): Georg Goergen
Mango Fruit fly (Ceratitis cosyra)The body and wing color is yellowish, with black spots. Adult mediterrenean fruit flies are 4-6 mm long,The wings are spotted or banded with yellow and brown margins.
(c) R. C. Copeland, icipe

1. Geographical Distribution in Africa

Geographical Distribution of the Fruit fly in Africa (red marked), updated on 10 July 2019, Source CABI.

Fruit flies (diverse species) have been recorded in all African countries. The Mediterranean fruit fly is the most widely distributed.

General Information on Pest and Damage

Fruit flies cause direct damage by puncturing the fruit skin to lay eggs. During egg laying bacteria from the intestinal flora of the fly are introduced into the fruit. These bacteria cause rotting of the tissues surrounding the egg. When the eggs hatch, the maggots feed on the fruit flesh making galleries. These provide entry for pathogens and increase the fruit decay, making fruits unsuitable for human consumption. Generally the fruit falls to the ground as, or just before the maggots pupate. In fruits for export, fruit flies cause indirect losses resulting from quarantine restrictions that are imposed by importing countries to prevent entry of fruit flies. Nearly all fruit fly species are quarantine pests. 

Major species of fruit flies attacking crops in Africa: 

  • African invader fly (Bactrocera invadens)
  • Melon fly (Bactrocera cucurbitae)
  • Pumpkin fly (Dacus bivittatus)
  • Jointed pumpkin fly (Dacus vertebratus)
  • Mediterranean fruit fly or medfly (Ceratitis capitata)
  • Natal fruit fly (Ceratitis rosa)
  • Mango fruit fly or Marula fruit fly (Ceratitis cosyra)

Host Range

Fruit flies attack soft, fleshy fruits of a wide variety of fruit and vegetable crops. 
The Mediterranean fruit fly Ceratitis capitata feeds and causes damage to a very wide range of crops. 
Major host plants of Ceratitis cosyra include mango, guava, sour orange, marula, wild custard apple and wild apricot.
Ceratitis rosa is recorded from over 100 plant species. In Africa it attacks mango, papaya, guava and custard apple. It is also a common pest of arabica coffee in eastern Africa. 
Ceratitis fasciventris is a major pest of mango, guava and coffee in eastern and western Africa. 
Bactrocera invadens, a new species recently introduced into East Africa, attacks primarily mango, although it has been reared from several other plants (e.g. tomato, banana, guava, marula, avocado). 
Bactrocera cucurbitae, Dacus bivitattus, D. ciliatus and D. frontalis are pests mainly of cucurbit crops. 

Mediterranean fruit fly (Ceratitis capitata). Adult mediterrenean fruit flies are 4-7 mm long, brightly coloured, usually in brown-yellow patterns. The wings are spotted or banded with yellow and brown margins.
(c) Scott Bauer, USDA Agricultural Research Service, www.insectimages.org
Fruit fly maggots in watermelon fruit. They are about 1cm long
(c) A. M. Varela, icipe
Egg laying marks by fruit flies on an orange fruit
(c) A.A Seif, icipe
Fruit fly (Bactrocera invadens) attack on green banana
(c) M. K. Billah, icipe
Mango fruit fly (Ceratitis cosyra) damage symptoms on mango
(c) M. K. Billah. icipe

Symptoms

Damage symptoms vary from fruit to fruit. Attacked fruit usually shows punctures (made by females while laying eggs). Around these a necrosis may occur. Small holes on the fruits are visible when the maggot leaves the fruit. The affected part of the fruit becomes soft and colours prematurely.

Internal fruit fly damage symptoms on courgette
(c) M. K. Billah, icipe
Internal fruit fly damage symptoms on mango
(c) M. K. Billah, icipe

Affected plant stages

Fruiting stage. 
 

Affected plant parts

Fruits/pods. 

Symptoms by affected plant part

Fruits/pods: internal feeding; lesions; abnormal exudates; visible mould; discolouration; odour.

3. Biology and Ecology of Fruit Flies

The morphology of the various fruit fly species is similar. 

Eggs of fruits flies are small, white, and slender. They are laid under the skin of fruits in groups of 3 to 8 eggs, depending on the species. The flies lay eggs on mature green and ripening fruit. Some species may lay eggs in unripe fruitlets. Eggs hatch within 1 to 2 days. 

The larvae are whitish maggots. They feed on the fruit flesh causing the fruit to rot. After 4 to 17 days the maggots leave the fruit, making holes in the skin, and drop to pupate in the soil. 

Pupa of the Mediterranean fruit fly (Ceratitis capitata) in the soil.
(c) A. M. Varela, icipe

The pupae are white, brown or black and 4 to 12 mm long. They are found in the soil 2 to 5 cm beneath the host plant. The flies emerge from the pupae 10 to 20 days after pupation depending on climatic conditions. 

Fruit Fly (Ceratitis fasciventris).  Adult Ceratitis fasciventris are 4.5-6 mm long, brightly coloured, usually in brown-yellow patterns. The wings are spotted or banded with yellow and brown margins.
(c) R. C. Copeland, icipe

Adult fruit flies are 4 to 7 mm long, brightly coloured, usually in brown-yellow patterns. The wings are spotted or banded with yellow and brown margins.

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 Fruit flies.

5. Cultural practices

Orchard sanitation

Poorly managed or abandoned orchards can result in build up of fruit fly populations. Remove fruits with dimples and oozing clear sap. This method, although laborious, is more effective than picking rotten fruits from the ground, as the maggots may have left the fruits to pupate. To be effective this has to be done regularly (twice a week for the entire season). Kill the maggots by burning, burying or trying collected fruits in black plastic bags and exposing them to the heat of the sun for a few hours to kill the maggots. Alternatively, feed fruits to pigs or poultry. When burying fruits, ensure that the fruits are buried at least 50 cm (about two feet) deep to prevent emerging adult flies from reaching the soil surface.
 

Destruction of fallen fruits infested by fruit flies by putting them in black plastic bags, tying the bags and exposing them to the sun.
(c) M. K. Billah, icipe

Early harvesting

Harvesting crops early when mature green helps protect some crops from fruit fly damage. Fruit flies cannot develop in certain fruits such as papaya, banana and sapodilla when they are green. Only ripe fruits are good hosts. However, in other crops, such as mango this practice is not effective as some fruit fly species like Bactrocera invadens and Ceratitis cosyra are capable of infesting even immature or green mangoes.

6. Biological pest control

Natural enemies

Several natural enemies can contribute to the suppression of fruit flies. Major natural enemies are parasitic wasps (parasites the maggots of fruit flies) and predators such as rove beetles, weaver ants, spiders and birds and bats. In particular weaver ants have been shown to be very efficient in protecting fruit trees from pests, including fruit flies. These ants pray on fruit flies, but most important their presence and foraging activity hinders the fruit flies from laying eggs, resulting in reduced fruit fly damage, as shown in mango orchards in Benin (Van Mele et al., 2007). 

Although natural enemies alone do not give satisfactory control of fruit flies, efforts should be made to protect them, and to complement their effect on fruit flies with other management options. 

Parasitoids 
Tiny wasps (e.g. Bracon spp.) parasitise the maggots of fruit flies. Eggs and larvae of these parasitoids are found inside the bodies of the maggots. The parasitoid larvae are tiny, cream-coloured grubs that feed in or on other insects. Adult wasps feed on nectar, honeydew or pollen before laying eggs. Dill, parsley, yarrow, zinnia, clover, alfalfa, parsley, cosmos, sunflower, and marigold are flowering crops that attract the native braconid populations and provide good habitats for them.
 

Braconid wasp
(c) Scott Bauer, USDA Agricultural Research Service, Bugwood.org

The image shows a braconid wasp parasiting a caterpillar. 

For more information on natural enemies click here.

7. Biopesticides and physical methods

Pyrethrum

To control fruitflies, a spray with a pyrethrum solution can be used. It will kill bees if they are sprayed directly, but it does not leave poisonous residues. The best time to use it is in the evenings (after 6 pm) most of the bees are back in their hives. 
There is a product commercially available called Flower-DS(r) (available at the Hygrotech Company, contact-addresses below). This product is made of natural pyrethrum and is acceptable in organic certified systems. Artificial pyrethroids will work as well if you are not concerned about organic certification, but they are stronger and will leave residues on the fruits and leaves, which are poisonous to other animals, to useful insects and to humans.

  • Precautions: Be careful to spray late in the evening. Follow the spraying instructions. Wear masks and skin protection. All insect poisons are also poisonous to humans even if coming from natural sources.
  • Frequency of spraying: Start shortly after beginning of flowering, and repeat approx every 5 days or according to counts.
  • Please check the insect trap information to count your fly population. If no flies are trapped – there is no need to spray.

Neem

Frequent applications of neem can keep fruit fly attack to a minimum.
For more information on neem click here.

Fruit fly trap (Lynfield or bucket trap)

The Lynfield trap is cheap and easy to make. It is made of a cylindrical plastic container with 4 holes evenly spaced on its sides, a lid, a wire hanger and a bait basket (if it is to be used with a dry attractant). Similar traps can be made locally using ‘Kimbo’ or ‘Blue Band’ tubs or similar plastic containers or plastic bottles. 

They can be used with either specific attractants such as methyl eugenol or food baits such as protein hydrolysates or yeast or a peace of fruit (banana, mango). Also vinegar is a very good attractant. (Methyl eugenol attracts males of Bactrocera species and of a few Dacus species). Food baits attract both males and female fruit flies, they are not species specific, and also attract other insects, including natural enemies. 

Several types of commercial fruit fly baits exist but are not locally available or registered. 

Use food baits that attract a whole range of fruit fly species in the orchard such as protein hydrolysate (Nulure(r), Buminal(r), Solbait(r)). An alternative is waste brewers’ yeast at a rate of 45 ml per litre water. Use about 250 ml of the mixture in each trap. Add one tablespoonful of borax (di-sodium tetraborate) to each trap to prevent rotting of the flies caught.

A simple fruit fly trap is made as follows: 

  • Take a plastic bottle
  • As bait, use 1/2 cup vinegar, mix with water
  • Add 4-6 drops liquid dish soap (it heavies down the wings and the fruit flies drown), do not stir
  • Then take a pen or pencil and poke 4 to 5 holes in the plastic, just big enough for a fruit fly to fit into, about 7mm. Once a fruit fly crawls in, it cannot get out. You would think they would just fly back out through the holes, but they will not! If you see fruit flies crawling around on the surface of your plastic container but not going inside, make the holes larger
  • Hang the bottle in an area where you have seen most fruit flies. Depending on the amount of fruit flies you have, you can expect to start seeing the bottle fill up within just a few hours.
Fruit fly trap
(c) A.M. Varela and A.A. Seif, icipe
Homemade fruit fly trap
(c) A.M.Varela, icipe

The trap is filled with bait and hanged on the tree about 2 to 4 m above the ground within the canopy layer, in a semi-shaded spots, preferably in the upwind part of the canopy. The trap should be hanged in such a manner that branches and leaves are nearby, but not touching the trap. Traps should be hanged 10 to 50m apart, depending on the bait used. Collect catches weekly and sieve them. 

Fruit bagging

Bagging prevents fruit flies from laying eggs on the fruits. In addition, the bag provides physical protection from mechanical injuries (scars and scratches). Although laborious, it is cheap, safe, and gives a more reliable estimate of the projected harvest. Bagging not only protects fruit from fruit fly damage but protect the fruit from physical damage improving the market appearance of fruits. However, it is only practicable on small trees. 

How to make a bag? 

Cut old newspapers measuring 15 x 22 cm or 12.5 x 27.5 cm for mango and for fruits of similar size. Double the layers, as single layers break apart easily. Fold and sew or staple the sides and bottom of the sheets to make a rectangular bag. 

How to bag a fruit? 

Blow in the bag to inflate it. Remove some of the fruits, leaving one on each cluster. Insert one fruit per bag then close the bag using coconut midrib or firmly tie top end of bag with string or wire. Push the bottom of the bag upwards to prevent fruit from touching the bag. Use a ladder to reach as many fruits as possible. Secure the ladder firmly on the ground and for bigger and higher fruits trees, secure or tie the ladder firmly on big branches. 

Mango fruit bagging in an orchard in Kenya to prevent infestation by fruit flies.
(c) M. K. Billah, icipe

Reminders 
Bagging works well with melon, bitter gourd, mango, guava, star fruit, and banana. Whole banana bunches may be bagged inside banana leaves. Start bagging the mango fruit 55 to 60 days from flower bloom or when the fruits are about the size of a chicken egg. 

When using plastic bags, open the bottom or cut a few small holes to allow moisture to dry up. Moisture trapped in the plastic bags damages and/or promotes fungal and bacterial growth that can cause diseases. Plastic also overheats the fruit. Bags made of dried plant leaves are good alternatives to plastic. 

Remove the bags during harvest and dispose of them properly. 

8. Information Source Links

  • Secretariat of the Pacific Community, (2001). Fruit fly control methods for Pacific Island Countries and Territories. Pest Advisory Leaflet No. 40. Plant Protection Service, Secretariat of the Pacific Community. www.researchgate.net
  • CABI. (2005): Crop Protection Compendium, 2005 Edition. (c) CAB International Publishing. Wallingford, UK. www.cabi.org
  • ICIPE (2006). A Field Guide to the Management of Economically Important Tephritid Fruit Flies in Africa. S. Ekesi and M. K. Billah (editors). ISBN: 92-9064-179-7.
  • ICIPE (2006): A Guide to IPM in Mango Production in Kenya. By Ana Milena Varela, Abdurabi Seif and Brigitte Nyambo. www.icipe.org
  • Organisation for Non-Chemical Pest Management in the Tropics (OISAT) www.oisat.org
  • Van Mele, P., Vayssieres, JF., Van Tellingen, E. and Vrolijks, J. (2007). Effects of an African Weaver Ant, Oeocphylla longinoda, in Controlling Mango Fruit Flies (Diptera: Tephritidae) in Benin. Journal of Economic Entomology. 100(3): 695-701.

9. Contact Links

For information on small scale farming techniques, seeds, equipment and insecticides (e.g. pyrethrum solution).
HYGROTECH EAST AFRICA, LTD
Region :KENYA / TANZANIA
Address :P.O.Box 41446, Nairobi, Tigoni Centre, Limuru Road, KENYA
Phone :+254 (0) 20 205 3916/  0722 205 148
E-Mail: info@hygrotech.co.ke


 

Resource Links

Credit: Biovision-Infonet

Information Source Links

  • AIC, Ministry of Agriculture, Nairobi Kenya (2003). Fruits and Vegetables Technical Handbook
  • CAB International 2000 and 2005. Crop Protection Compendium. Wallingford, UK. www.cabi.org
  • Griesbach, J. (1992). A guide to propagation and cultivation of fruit trees in Kenya. Schriftreihe der GTZ, No. 230. Eschborn, Germany. ISBN: 3-88085-482-3.
  • Griesbach, J. (2003). Mango Growing in Kenya. World Agroforestry Centre (ICRAF). ISBN 92 9059 149 8. www.worldagroforestry.org
  • Institute for Tropical and Subtropical Crops (ARC-LNR) (1998). The Cultivation of Mangoes. Compiled and edited by E.A. de Villiers. ISBN: 0-620-22320-0
  • Mango organic cultivation guide, 2001, Naturland. Available online www.naturland.de
  • Neuenschwander, P. (2003). Biological control of cassava and mango mealybugs. In Biological Control in IPM Systems in Africa. Neuenschwander, P., Borgemeister, C and Langewald. J. (Editors). CABI Publishing in association with the ACP-EU Technical Centre for Agricultural and Rural Cooperation (CTA) and the Swiss Agency for Development and Cooperation (SDC). pp. 45-59. ISBN: 0-85199-639-6.
  • Nutrition Data. www.nutritiondata.com.
  • OISAT (Online Information Service for Non-Chemical Pest Management in the Tropics). www.oisat.org
  • Tandon PL, Lal B. (1978). The mango coccid Rastrococcus iceryoides Green (Homoptera: Coccidae) and its natural enemies. Current Science, 47(13):467-468.
  • Varela, A.M., Seif, A., Nyambo, B. (2006). A Guide to IPM in Mango Production in Kenya. ICIPE. Modern Lithographic Ltd., Nairobi, Kenya. www.icipe.org

Stem-end rot

Stem-end rot (Dothiorella dominicana, Botryodiplodia theobromae, Phomopsis mangiferae)

Credit: Biovision-Infonet

Mango stem end rot (Dothiorella dominicana, Botryodiplodia theobromae, and/or Phomopsis mangiferae)
(c) A. M. Varela & A.A. Seif, icipe

Symptoms consist of a dark-brown, firm decay starting at the stem-end of the fruit and developing rapidly to involve the whole fruit. The fungi survive on dead twigs and branches where they produce large numbers of spores. During wet weather, these spores are spread to adjacent fruits where infection occurs. The rot generally does not develop until the fruits begin to ripen.

Chemical sprays are neither recommended nor necessary.

What to do:

  • Prune dead twigs and branches.
  • Avoid harvesting immature fruits.
  • Cool fruits immediately after harvesting.
  • Store fruits in well-ventilated containers.

Malformation

Malformation (Fusarium subglutinans)

Credit: Biovision-Infonet

The fungus produces compounds that have hormonal effect on the plant. The fungus is easily spread by grafting and infected nursery trees. In the orchard the disease spreads slowly despite of masses of spores produced on the panicles.

Symptoms consist of affected flowers taking on, to a greater or lesser extent, the appearance of a cauliflower head. The axes of the panicles are shorter and thicker than normal, branch more often, and a profusion of enlarged flowers is produced. The affected panicles retain their green colour, are sterile and produce no fruits. In the nursery, vegetative malformation can occur. Eriophid mites are believed to be vectors of the disease and their damage symptoms are similar to those caused by F. subglutinans. Symptoms consist of buds producing short shoots and small brittle leaves creating a compact “witches broom” appearance.

What to do:

  • Remove affected parts. These could either be burned or placed in plastic garbage bags and exposed to the sun for a day or two to be burned.

Bacterial black spot

Bacterial black spot (Xanthomonas campestris pv. mangiferaeindicae)

Credit: Biovision-Infonet

Bacterial black spot (Xanthomonas campestris pv. mangiferaeindica) on mango leaves
(c) Courtesy EcoPort (http://www.ecoport.org): Jurgen Kranz
Bacterial black spot (Xanthomonas campestris pv. mangiferaeindica) symptoms on a mango fruit. Note star-like cracks on the fruit
(c) A.A.Seif, icipe

Bacterial black spot is rain related and is spread through rain splash within an orchard. Long-distance spread is by infected planting material. Important factors in infection are very small wounds that are easily caused by wind and wet weather. On leaves, spots are angular, dark, shiny in appearance and delimited by veins.

Fruit spots start off as water soaked and then become raised and black. Later they crack open in the centre in form of a star. In wet weather, these spots exude gum. Fruit becomes more susceptible with age.

What to do:

  • Consider which cultivars are appropriate to grow in wet, humid areas. “Heidi”, “Kensington”, “Sensation” and “Tommy Atkins” are tolerant to bacterial black spot. Keitt and Kent are highly susceptible to the disease. No varieties are immune.
  • Prune off diseased twigs and establish windbreaks around the orchard.
  • Copper sprays are the only method of combating the disease and are not always successful when disease pressure is high. 1 or 2 post-harvest copper sprays to cover the post-harvest flush and tail end of the rain season are effective in reducing inoculum (disease) pressure for the following season.
  • Monitor for the disease weekly.

Powdery mildew

Powdery mildew (Oidium mangifera)

Credit: Biovision-Infonet

Mango panicle affected by powdery mildew. Note white powdery growth and low fruit set.
A.M. Varela, A. A. Seif, icipe
Powdery mildew (Oidium mangifera) on young mango leaves
(c) A. M. Varela & A.A. Seif, icipe
Powdery mildew on young mango leaves
(c) A.A. Seif
Powdery mildew on mango panicle
(c) A.A. Seif

It appears as a white, powdery growth on leaves, flowers and young fruit. Infected leaves curl and flowers fail to open and drop from the tree without forming a fruit. The disease is spread by wind and can spread very rapidly. It is more prevalent in dry weather when humidity is high and nights are cool. The fungus survives from season to season in dormant buds. The flowering stage is the most critical stage for infection.

What to do:

  • Consider appropriate cultivars that grow in cool, dry areas. Alphonse, “Kent” and “Zill” are highly susceptible to mildew. “Haden” and “Keitt” are moderately susceptible and Sensation and Tommy Atkins are tolerant.
  • Monitor for the disease weekly.
  • Spray a solution of: baking powder (6 teaspoonfuls), white oil (3 teaspoonfuls) and white bar soap foam in 15 litres of water. This solution has been shown to control powdery mildew.
  • Sulphur based fungicides can effectively control powdery mildew if appropriately used.

Anthracnose

Anthracnose (Colletotrichum gloeosporiodes)

Credit: Biovision-Infonet

Anthracnose on ripe mango fruit
(c) A.A. Seif & A.M. Varela, icipe 

(Colletotrichum gloeosporioides). Anthracnose initially appears as small black spots. On leaves, the spots can grow to form an irregular patch. On young fruit, pin-sized, brown or black, sunken spots develop.

Anthracnose tear stain symptoms on a mango fruit
(c) A.A. Seif

The most serious and widespread fungus is anthracnose. Anthracnose initially appears as small black spots. On leaves, the spots can grow to form an irregular patch. On young fruit, pin-sized, brown or black, sunken spots develop. Sometimes, a “tear stain” pattern develops on fruit. It is an important problem after harvesting the fruit, especially during transport and storage, where fruit can develop round, blackish sunken spots. The fungus is spread by rain splash and survives from season to season on dead leaves and twigs. Rainy weather during blooming and early fruit set will favour the development of anthracnose.What to do:

  • Use tolerant varieties. “Tommy Atkins” is less susceptible to anthracnose than “Haden”, “Sensation” and “Zill”.
  • Cut-out dead branches and twigs and dead leaves. Completely remove them from the mango orchard.
  • Monitor for the disease weekly.

CH. 1 Information on Diseases

Biological methods of plant protection

The most usual diseases with mango trees are fungus and bacterial diseases. The first important preventative measure is make sure that the propagation segments are healthy. The scions that were raised in tree nurseries and whose origins are maybe unclear, should be carefully examined. They shall not have been treated with any synthetic or chemical agents.

Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most wide-spread disease among mangoes. The varieties vary in susceptibility. Colletotrichum gloeosporioides causes anthracnose on fruits, and drop of flowers on young branches. Anthracnose always appears as a result of scurvy (Elsinoe mangiferae). Fruits stricken with anthracnose can be plunged into a hot water bath (3- 5 min. at 55degC), in order to kill off the fungus. Preventative measures are nevertheless preferable, to preclude injuries and an infection with scurvy, because anthracnose can usually only take a hold on damaged fruits that are also affected by scurvy. A case of scurvy can usually be prevented by removing all dead plant material (branches, leaves and fruit). In exceptional cases, the fungus can be brought under control again with copper strays.

While anthracnose generally attacks ripe fruits (and blossoms), a bacterial infection from Erwinia sp. can also affect young fruit. The symptoms are very similar to the flecks caused to the leaves and fruit by anthracnose. The bacteria usually survive in the ground – a heavy rainfall will then splash the spores against the lower leaves and fruits. Covering the ground can therefore help to protect against this. Active life in the soil will also help to prevent an explosive growth of bacteria. Sites where it can rain inside the blossoms can also be a problem.

Young fruit and also blossoms can be damaged by powdery mildew (Oidium mangiferae). This fungus grows during warm weather with high humidity. It attacks flowers and young fruits. A case of powdery mildew can dramatically affect the harvest. An open, well-ventilated orchard can prevent mildew. In acute cases, mildew can also be brought under control with sulphur. When carrying this out, there should be no wind blowing, and the leaves should still be moist with dew.

The leaf spot disease (Cercospora mangiferae) on mangoes is visible as dented spots on leaves and fruit. The same applies for this fungus, an open and quick-drying tree population is the best protection against infection. Fruit infected with Cercospora can no longer be sold, furthermore, both the leaf spot disease and scurvy prepare the way for anthracnose. In exceptional cases, the leaf spot disease can be brought under control copper sprays.

CH 1. Information on pests

Credit: Biovision-Infonet

Information on Pests

Biological methods of plant protection

The worst pests for mangoes include fruit flies, cotton scales, mealybugs, cicadas and black flies (create honey dew). They can cause a lot of damage. Yet they all have natural enemies, such as e.g. ladybird larvae, wasps, spiders and parasitic  fungi (e.g. with cicadas and black flies).

An ecological plantation with a variety of crops and a sufficient amount of vegetation cover will provide enough natural enemies to combat the pests that measures against them unnecessary. Cicadas are averse to open, well ventilated soil, also drain the soil well to avoid wet patches.

In emergencies, the following methods should help:

Scale insects can be regulated with a ‘winter-spraying’, i.e. with paraffin oil (white oil) shortly before the larvae hatch from their eggs. The paraffin oil is sprayed on as a 3 % water emulsion.

Plant spraying mixtures made of stinging nettles or neem can be used against cicadas. The worst damage occurs during blossoming, so the plantation should be checked regularly around this time in order to make up the brew and spray it early enough.

Mealybugs lay their eggs on the ground next to the trunk. By wrapping smooth plastic bands around the trunk, the larvae can be prevented from infesting too large an area. Should they infest the tree, a solution of 1% soft soap (potassium soap) is quite effective.

Black fly can be kept under control by useful insects. A variety of prospatella species can be of use here. This requires a good functioning control system, because the useful larvae need to be made available for release in time. Where this is not possible, spraying white oil shortly before the pests hatch, as such as with scale insects can be sufficient.