On the radar: Cowpea aphid activity on faba bean

We recently received reports of cowpea aphid (Aphis craccivora) activity in faba bean crops across the South East.

Cowpea aphids are glossy, black insects characterised by distinctive black and white legs. They usually infest a range of legume crops, including lentils, faba beans, field peas, lupins, lucerne, clover, and medics.

In spring, populations can build rapidly under warm, dry conditions and may cause significant sap-sucking damage, particularly to younger tissues and flowering shoots. Heavy infestations can result in distorted growth, honeydew deposits, and sooty mould.

Colonisation often occurs when winged aphids disperse from surrounding pastures or weeds following rainfall and weed flushes.

Regular monitoring should begin early in the season and continue through flowering, with particular attention to crop edges, weedy borders, and irrigated or sheltered areas where aphids often first appear.

Natural enemies like ladybird beetles, lacewings, hoverflies, and parasitoid wasps, which are highly active in the current spring weather, can play an important role in suppressing populations. Preserving these beneficials by avoiding unnecessary or broad-spectrum insecticide use is critical for long-term control.

If chemical intervention becomes necessary, always:

• refer to current product labels
• observe withholding periods and harvest intervals to ensure residues remain within allowable limits.

Keep in mind that many insecticides applied to target other pests (native budworm, for example), will also affect cowpea aphid populations.

Cowpea aphid on lucerne (photo by M. Ehsangar)