Cowpea aphids

Be on the lookout for cowpea aphids in pulse crops; early infestations have been recorded

 

Cowpea aphid adult and nymph (Source: cesar)

 

Where have they been reported?

Cowpea aphids have been identified on volunteer faba beans in paddocks (near Shepparton in the Victoria’s Northern Country, and near Rupanyup in the Victorian Wimmera), and in emerging vetch crops in the Wimmera. In most cases, the aphids were winged, indicating that they have flown in from near or possibly distant autumn hosts. The presence of cowpea aphid in the Wimmera crops is particularly interesting given the extensive period of dryness and lack of local ‘green bridge’ on which aphids breed.

About the pest

The cowpea aphid (Aphis craccivora) is a widespread and common pest of legume and pulse crops in many parts of Australia. They have a wide range of host plants and can tolerate warm, dry weather conditions that cause many other aphid species to suffer. For detailed information on cowpea aphids, including their occurrence, lifecycle, behaviour, damage symptoms and management strategies, go to cowpea aphids.

Our advice

Although cowpea aphids are most prominent in spring, they are often active during autumn, as is clear from this year, and will persist through winter. We suggest regular monitoring of vulnerable crops in regions where there may have been an early build up. Cowpea aphids will not cause significant feeding damage to (or successfully colonise) canola plants; the likelihood of virus transmission is unknown. Thus, sprays in this crop to prevent feeding damage from cowpea aphids are not warranted.

The early appearance in the Wimmera region suggests they may appear on many legumes following an extensive migration. The presence of cowpea aphid in crops later in the season during bud formation to late flowering may also be important. Aphid numbers fluctuate greatly with weather conditions and are difficult to predict.

 

Sources of field reports of cowpea aphid

Ben Cordes – Agronomist, Tylers Hardware & Rural Supplies (Victorian Wimmera)

Bruce Larcombe – Agronomist, IK Caldwell (North East Victoria)