Main aphids in Africa: Black bean aphid ([i]Aphis fabae[/i]), Cabbage aphid ([i]Brevycoryne brassicae/Myzus persicae[/i]), Groundnut aphid ([i]A.craccivora[/i]), Cotton aphid ([i]A.gossypii[/i]), Russian wheat aphid ([i]Diuraphis noxia[/i]), Cypress aphid ([i]Cinara cupressi[/i])
Several species of aphids attack brassicas in East Africa:
The cabbage aphid (Brevicoryne brassicae)
The false cabbage aphid (Lipaphis erysimi)
The green peach aphid (Myzus persicae)
In particular the cabbage aphid is a major pest in the region. Cool, dry weather is most favourable for aphid development. Large numbers of aphids may kill small plants. Their feeding can distort leaves of older plants and causes leaf curl.
Often, the most serious problem associated with aphids is virus transmission. The cabbage aphid and the false cabbage aphid are vectors of virus diseases such as cabbage black ring spot, cabbage ring necrosis, and mosaic diseases of cauliflower, radish and turnip.
- Aphid colonies in the heads of cabbage are almost impossible to remove before marketing. Natural enemies can provide control, but they usually do not build up fast enough to keep heavy aphid populations below damaging levels. Extensive use of broad-spectrum insecticides like pyrethroids might induce resistance development in aphids and will eliminate natural enemies. For more information on Natural enemies click here.
- Insecticidal soaps provide control, and spot sprays of pyrethrum or neem can prevent build up of large populations.