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])
Aphids (Aphis gossypii, Myzus persicae)
Aphids (cotton aphid and green peach aphid) occur in colonies initially around tender plant parts (growing points, young stems and leaves, flower buds) and on the lower leaf surface. When numerous they can be found on all above ground parts of the plant. Aphids damage plants in three ways: by sucking their sap, excreting a sticky substance (honeydew) that coats the plants, or/and by transmitting viral diseases.
Feeding by aphids causes distortion (curling, wrinkling or cupping) of young leaves, chlorotic spotting and mottling of older leaves, and may lead to stunting and wilting of plants. Growth of sooty mould on honeydew excreted by aphids reduces photosynthesis and affects fruit quality.
Aphids cause indirect damage as vectors of important viruses such as alfalfa mosaic, chilli veinal mottle, cucumber mosaic, pepper mottle, pepper severe mosaic, pepper veinal mottle, potato Y and tobacco etch virus.
- Monitor regularly the crop.
Aphids are naturally controlled by parasitic wasps; predators such as ladybird beetles, rove beetles, hoverflies, cecidomyiid flies, anthocorid bugs, spiders and lacewings; and by fungal diseases.
The parasitic wasps Aphidius spp are common in Kenya, and help to maintain aphids under control provided no broad-spectrum pesticides are used for control of aphids or other pests.
- Whenever necessary spray only affected plants (spot spraying).Use biopesticides that are not harmful to natural enemies (for instance neem, ashes, soapy water).
- Neem products have a repellent effect and have been effective in reducing numbers of aphids on peppers when applied at 10 days intervals.