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Discuss the pests affecting beans, their symptoms and how they can be controlled

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1.Bean fly (Melanognomzaspencerellaphaseoli)
-Also called bean stem maggot
-A major seedling pest in the tropics and sub tropics
-Has a wide host range. Most hosts are in the genera Phaseolus, Glycine and Vicia
--also has alternative hosts which are normally under leguminous plants
-Most severe damage occur during dry season and can results in 100% plant loss
-The larvae is the one causing damage to seedlings

Symptoms:
i. Brown tumorous growth around the injury point (the point just above the soil level)
ii. Leaves turn yellow
iii. Plants are stunted and die
iv. The suvirving plants may produce pods which are small and containing few small seeds

Control:
i. Use of insecticides
-Applying appropriate insecticide such as carbofuran in the planting furrow or holes before planting.
-Treating seeds with appropriate insecticides before planting
-Use of foliar spray after seedling emergence
ii. Cultural control methods
-Combination of methods control such as early planting, eliminating of alternative host plants, destruction of crop residues and volunteer crops, crop rotation with non -host plants, and soil earthing up to encourage adventitious root formation.
iii. Biological control
- Has not been widely used
-Use of resistant varieties if available. No stable stand in east Africa germ plasm.

2.Bean Aphids (Aphis fabae)
-These are black soft bodied insects normally found in clusters around the growing points of stems, leaves and flowers.
-They are sucking insects and when present in large numbers cause damage by depleting plant sap and nutrients.
-The attack is common during dry spell.
-They also act as vectors of certain viruses.
-Aphids have wide hot range affecting both cropped legumes and wild legumes.

Symptoms:
i. Yellowing of leaves
ii. Leaves are distorted
iii. In severe cases the leaves dry and the whole plant wilt
iv. Formed pods are small with few seeds resulting in decline in yield

Control:
i. Spray with insecticides

Titany answered the question on August 16, 2021 at 11:20

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Discuss the pests affecting beans, their symptoms and how they can be controlled

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