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])
Cotton aphid (Aphis gossypii)
Cotton aphids are about 1-3 mm long, and variable in colour from yellow to yellowish green or very dark (almost black) with two cornicles (projections) on the rear end and long antennae. They suck sap preferably from tender shoots and the underside of young leaves. Feeding by aphids may result in crinkling and cupping of leaves, defoliation, square and boll shedding and stunted growth.
Honeydew (a sugary liquid) excreted by aphids accumulates on the upper surface of leaves and sooty mould develops. Honeydew can contaminate the fibre if the bolls are open, causing problems in processing the lint.
- The cotton aphid is attacked by a range of natural enemies. The most important are ladybird beetles, hoverflies, lacewings and parasitic wasps. They usually keep aphids under control.
- Healthy cotton plants can tolerate a fairly high number of aphids.
- Avoid plant stress by giving neither too little nor too much manure. Avoid water stress and water logging.
- Intercrop cotton with maize or sorghum to create a natural balance of pests and natural enemies.
- Use yellow water or sticky traps.
- Spraying maybe necessary in the case of high aphid infestation or if the honeydew affects the lint in open bolls. If this is the case, use plant extracts such as neem leaf and seed extracts, ginger rhizome extract, and custard apple leaf extract for control of aphids.
- 3% potassium soap in acute cases; in extreme cases use nicotine extract, neem, chilli, garlic, or Lantana camara