Lesser grain borer(Rhyzopertha dominica). Adults are 2-3 mm in length and reddish-brown in colour (shown on wheat grains). (c) Clemson University – USDA Cooperative Extension Slide Series, United States, bugwood.org
Damage to cassava chips by Larger Grain Borer (c) GTZ
A number of beetles feed on dry cassava causing post harvest losses. In Benin Republic the most common are Dinoderus sp., Carpophilus sp., the coffee bean weevil (Araecerus fasciculatus), the lesser grain borer (Rhizopertha dominica), and more recently, the larger grain borer (Prostephanus truncatus).
Infestation by these insects is heavier in the rainy season than in the dry season, is more prevalent in the humid zone than in the savannah, and is found more in large chips than in smaller ones.
Maximum infestation was found after 6 to 8 months in storage, at which time chips would fall into dust when squeezed (Bokanga, IITA, FAO).
What to do:
Use
botanicals or plant parts to protect stored cassava. There are reports
in Kenya, that the larger grain borer can be effectively repelled by
storing cassava or grains with a fairly large amount of dried lantana or
eucalyptus leaves (Personal communication, field officer of Meru
herbs). Neem is also reported to be effective.
Variegated grasshopper(Zonocerus variegatus) (c) Georg Goergen (Courtesy of EcoPort, www.ecoport.org)
Grasshoppers such as the variegated grasshopper (West to East Africa south of the Sahara), and the elegant grasshopper (Z. elegans) (Southern Africa and East Africa) are brightly coloured grasshoppers.
Adults are dark green with yellow, black and orange marking on their bodies. Nymphs are black with yellow markings on the body, legs and antenna and wing pads.
Female grasshoppers lay many eggs just below the surface of the soil in the shade under evergreen plants, usually outside cassava fields.
Eggs are laid in masses of froth, which harden to form sponge-like packets, known as egg pods, which look like tiny groundnut pods. Eggs start to hatch at the beginning of the main dry season.
Grasshoppers attack a wide range of crops mainly in the seedling stage. They feed on cassava plants, chewing leaves and stems and may cause defoliation and debark stems.
This is particularly severe in fields next to the bush when the dry season is prolonged.
What to do:
Hand pick grasshoppers. This is feasible in small plots.
Locate and dig egg-laying sites to expose and destroy the eggs before they start to hatch early in the dry season. However, egg pod destruction has to be done over a wide area in the wet season in order to be effective. This will require participation of farmers on many neighbouring farms. If only one neighbour destroys the eggs in his/her farm, the grasshoppers will later invade the farm from the neighbouring farms and bushes.
When available, use biopesticides. IITA researchers and partners have developed an environmental friendly biopesticide “Green Muscle(r)”. It is based on a naturally occurring fungus strain indigenous to Africa (Metarhizium anisopliae) which is deadly to locusts and grasshoppers but reportedly does not damage other insects, plants, animals, or people. Typically 70 to 100% mortality rates were obtained after 8 to 28 days of application ( www.iita.org). The bioinsecticide “Green Muscle(r)” is effective in grasshopper management in outbreak situations. However, it is costly and currently, it is only available in South Africa and West Africa.
Use neem extracts. Neem protects cassava from grasshopper damage. It acts as antifeedant (grasshoppers stop feeding when exposed to neem products) and affects development of the grasshoppers (Nicol et al, 1995; Olaoifa and Adenuga, 1988). In Nigeria, the following neem products have given good control of Z. variegatus on cassava: 1.) Emulsifiable concentrate of neem oil at 0.5% to 2% applied at 8-day intervals or at 3-4% at 10-day intervals, 2.) Aqueous neem kernel water extracts (NSKE) at 7-10% applied every 12 days and aqueous neem leaf water extracts (NLWE) 50% applied every 6 days. Aqueous extracts from neem leaves were less effective than neem seed extracts (Olaoifa and Adenuga, 1988).
Ng’ombe akindungwa na nyuki wengi huduma ya kwanza ni gani vet akiwa hapatikani haraka?
English Translation: Which first aid should I give a cow that has been stung by bees if the Vet is not available?
From: Kelly, County: Meru, Kenya
Discussion:
Kelly’s cows were attacked by a resting swarm of bees on a tree near her home when they got disturbed with throwing stones by some children. She was not at home at the time and the cows were in a zero-grazing unit. The neighbours came to help. Two cows died and the remaining one is in poor condition. The vet was not available to attend to the cows fast. When the animal is away from the bees one can look for stingers and remove them by scraping with say a fingernail. Emergency treatment by a vet is required and especially if the animal is allergic.
Dear Kelly,
It is unfortunate to lose your cows by bees attack after they were disturbed with throwing stones by children. Sorry for losing the cows. In an event an animal or animals are attacked by bees, without putting yourself in risk as bees can as well attack you, make sure you are safe and protected, and then release the animal if tethered or in an enclosure like a zero-grazing unit. The animal may run about, take care it does not run to you as an injured animal may attack you suddenly or may run into the road. When the animal is away from the bees look for stingers which the bees lose after stinging. The stingers continue to inject the venom for some time or until they are removed. If they are found on the animal, remove them by scraping them. Do not pull them out or twist them as this would squeeze out more venom into the animal. Please call a vet doctor immediately to give the animal emergency treatment because bees stings whether few or many are dangerous and more so if the animal is allergic like in the case of your cows.
Livestock and pets are likely to be stung if the bees are disturbed. Honey bees do not strike until they are provoked. Please do not tether or keep livestock in an enclosure like zero-grazing unit near bee hives and nests. Bees should not be disturbed by throwing stones at, request a bee expert to remove bees that are in unusual place, and do not use insecticides sprays on bee nests as this would arouse them. Bees’ stings are dangerous as they cause allergic reaction in animals and people. Bee stings reveal symptoms associated with local reactions, pain, swellings, cellulitis, systemic allergic reactions, urticarial rush, asthma, and anaphylactic shock and fatality. These signs may vary depending on the type and quantity of the venom, stinging site, number of stings and individual sensitivity.
Scale insect. This is not the cassava scale, but an armored scale (related species) (c) USDA ARS, Bugwood.org
It is a mussel-shaped scale with an elongated silvery-white cover and about 2-2.5 mm long. This scale may cover the stem with conspicuous white secretions, and eventually the leaves. This scale sucks from the stem and dehydrates it.
The leaves of attacked plants turn pale, wilt and drop off. Severely attacked plants are stunted and yield poorly. Scale attack can kill cassava plants, in particular plants weakened by previous insect attack and drought. Stem cuttings derived from infested stem portions normally do not sprout.
What to do:
Apply of organic matter to improve soil fertility.
Selection of clean (scale free) planting material.
Destroy infested stems.
Avoid use of pesticides in the cassava field or in neighbouring crops, which may kill natural enemies.
Two-spotted spider mite (Tetranychus urticae) . The adult female is 0.6 mm long. The male is smaller. (c) Warwick HRI, University of Warwick
Several species of red spider mites also occur on cassava, mostly on the older leaves. Adults are about 0.6 mm long. Initial symptoms are yellowish pinpricks along the main vein of mature leaves. Spider mites produce protective webbing that can be readily seen on the plant. Attacked leaves turn reddish, brown or rusty in colour. Under severe mite attack, leaves die and drop beginning with older leaves. Most damage occurs at the beginning of the dry season.
What to do:
Conserve natural enemies. Local natural enemies usually control these spider mites and no further control measures are needed.
Avoid planting next to infested fields.
Avoid use of broad-spectrum pesticides, in particular pyrethroids; this may lead to spider mite outbreaks.
Cassava green mite(Mononychellus tanajoa) and eggs. Real size 0.8 mm, egg 0.2 mm. (c) F. Haas, icipe
Damage by the cassava green mite(Mononychellus tanajoa) (c) A. M. Varela, icipe
This mite is green in colour at a young age turning yellowish as adult. Adult females attain a size of 0.8 mm. They appear as yellowish green specks to the naked eye.
They occur on the lower surface of young leaves, green stems and auxiliary buds of cassava. Damage initially appears as yellowish “pinpricks” on the surface of young leaves.
Symptoms vary from a few chlorotic spots to complete chlorosis. These symptoms are somehow similar to African cassava mosaic disease, and should not be confused.
Heavily attacked leaves are stunted and become deformed. Severe attacks cause the terminal leaves to die and drop, and the shoot tip looks like a “candle stick”. Green spider mites are major pests in dry season. Severe mite attack results in 20-80 % loss in tuber yield.
Predatory mites (mainly Typhlodromalus aripo and T. manihoti) introduced from South America, the home of the cassava green mite, have given effective control of the cassava green mites in Africa (Yaninek and Hanna, 2003).
What to do:
Whenever possible, use varieties with good tolerance to green mites (Examples from West Africa: “BEN 86052”, “MS6” and “NR8082”) (James et al, 2000).
Use clean plant material for planting.
Plant at the onset of the rains to encourage vigorous growth and thereby increase tolerance to mite attack. Cassava plants aged 2-9 months are the most vulnerable to infestation.
Practise intercropping. Cassava intercropped with pigeon pea has been reported to suffer less damage from cassava green mite than that grown on a pure stand in Nigeria. Higher tuber yields were obtained when cassava was intercropped with pigeon pea in triple and double rows than when it was alternated in a single row or in a pure stand (Ezulike and Egwuatu, 1993).
Striped mealybug(Ferrisia virgata) (c) F. Haas, icipe
It is a whitish mealybug with two longitudinal dark stripes, long glassy wax threads and two long tails. It attains a length of 4 mm. The stripped mealybug occurs on the underside of leaves near the petioles and on the stems.
It sucks sap but does not inject any toxin into plants. Severely attacked plants show general symptoms of weakening but do not show distortion.
It is a minor pest of cassava, and no control is usually required as is controlled naturally by natural enemies.
Red-Billed Quelae Bird is one of the most dangerous of all agricultural pests in Africa, and causes food shortages in many countries. The flock breeds at times of abundant rainfall and young are ready to move with the nomadic flock within six weeks,often coinciding with the ripening of grain crops. A nesting colony of Red-billed quelea can extend over hundreds of acres, and a single flock may number millions of birds, moving together in a synchronized fashion. Recent discussions about quelea bird pest control have started to turn towards prediction of breeding based on weather patterns (c) Courtesy EcoPort (http://www.ecoport.org) : C.Elliott.
Red-Billed Quelae Bird Nest The nest is made in the form of a pouch with a roof and an entrance near the top. The male is responsible for the construction which is completed by a remarkable technique of weaving strips of grass back and forth to form a mesh-like structure. This is why the quelea bird is called a ‘weaver bird’. If the nest is accepted by a female, she will enter and in due course produce a clutch of three eggs. (c) Courtesy EcoPort (http://www.ecoport.org) : C.Elliott
Wild Rat (c) Reg Mckenna, wikipedia
Free-range pig keeping (c) S. Gikonyo, Kenya
Angora and Galla goats (c) Anne Bruntse, BioVision
Birds, rodents, monkeys, pigs and domestic animals (cattle, goat and sheep) are common vertebrate pests of cassava.
Measures that help to manage damage by these pests include:
What to do:
Fence farms and set traps in the fence.
Cover exposed roots with soil.
Weed your cassava farm to discourage rodents pests.
Harvest roots as soon as they are mature (James et al., 2000).
Larger grain borer(Prostephanus truncatus). The adult beetle is 3-4.5 mm long. (c) NRI/MAFF. Reproduced from the Crop Protection Compendium, 2004 Edition. (c) CAB International, Wallingford, UK, 2004
The larger grain borer has been found infesting cassava chips in storage particularly during the rainy season in West Africa. This beetle is currently the most serious pest of dried cassava in storage. Weight losses as high as 70% after 4 months of storage have been reported elsewhere.
What to do:
Use botanicals or plant parts to protect stored cassava. There are reports in Kenya, that the larger grain borer can be effectively repelled by storing cassava or grains with a fairly large amount of dried lantana or eucalyptus leaves (Personal communication, field officer of Meru herbs). Neem is also reported to be effective.
The cassava mealybug is pinkish in colour. Its body is surrounded by very short filaments, and covered with a fine coating of wax. Adults are 0.5 – 1.4mm long. (c) G. Goergen (Courtesy of EcoPort, www.ecoport.org)
Parasitic wasp of mealybugs (c) A.M. Varela, icipe
Mealybug infestation on lower leaf surface of cassava plant (c) A.A. Seif
The cassava mealybug is pinkish in colour. Its body is surrounded by very short filaments, and covered with a fine coating of wax. Adults are 0.5-1.4 mm long. This mealybug does not have males. Females live for about 20 days and lay 400 eggs in average.
The lifecycle from egg to adult is completed in about 1 month at 27°C. It reproduces throughout the year and it reaches peak densities during the dry season. Mealybugs are dispersed by wind and through planting material.
The cassava mealybug strongly prefers cassava and other Manihot species; other host crops and wild hosts are only marginally infested. It sucks sap at cassava shoot tips, on the lower surface of leaves, and on stems.
During feeding the mealybug injects a toxin into the cassava plant causing deformation of terminal shoots, which become stunted, resulting in compression of terminal leaves into “bunchy tops”. The length of internodes is reduced, and stems are distorted.
When attack is severe plants die, starting at the plant tip, where most mealybugs are found.
Mealybug attack results in leaf loss and poor quality planting material (stem cuttings) due to dieback and weakening of stems used for crop propagation. Tuber losses have been estimated up to 80%.
The pest-induced defoliation reduces availability of healthy leaves, which are consumed as leafy vegetables in most of West and Central Africa. After the pest cripples plant growth, weed and erosion sometimes lead to total destruction of the crops.
In general, yield losses depend upon age of plant when attacked, length of dry season, severity of attack and general conditions of the plant. Mealybug damage is more severe in the dry than in the wet season.
The cassava mealybug was accidentally introduced to Africa from South America. After the first reports in the 1970s, the insect became the major cassava pest within a few years and spread rapidly through most of the African cassava belt.
The outbreak led to famine in several countries where cassava is a staple crop and particularly important in times of drought. In an attempt to control this pest natural enemies, mainly parasitic wasps and ladybird beetles, were introduced from South America.
The most effective has been the parasitic wasp (Apoanagyrus (=Epidinocarsis) lopezi), which has kept this mealybug at low levels, resulting on significant reduction of yield losses in most areas in Africa (Neuenschwander, 2003).
What to do:
Plant early in the rainy season to allow the cassava plants a good growth before the dry season. Strong plants are more likely to withstand pest attacks.
Use soil amendments and mulch to avoid moisture stress in sandy or poor soils. Mealybug numbers are higher on cassava grown on poor, sandy soils, and may cause damage in spite of the presence of natural enemies.
Avoid using infested plant material. Before planting cutting can be treated with hot water [by immersing them in heated water (mixing equal volumes of boiling and cold water) for 5-10 minutes just before planting] to kill all insects/mites and to avoid transfer into the newly planted field.
Avoid using pesticides on crops surrounding cassava fields. Although, no pesticides are used on cassava in Africa, insecticide drift from neighbouring fields may affect natural enemies that keep mealybugs and other pests under control.
Use of manure or other fertilisers can result in a reduction in the mealybug population because improved nutrition results in the production of larger parasitoid wasps with higher fertility levels. Mulch and fertilizer use also enhances the antibiotic properties of cassava against mealybug infestation.
