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Cowpea aphids

Research agronomist, Simon Craig (Birchip Cropping Group), has reported cowpea aphids attacking vetch and medics near Birchip, in the Mallee district of Victoria. Simon says 20-30 aphids could be found per stem and appeared to be causing some damage. The affected crops will be sprayed to prevent further build-up of aphid numbers. It is important to remember that in some cases the whole paddock may not require treatment, as aphid infestations often start at crop edges. If most of the infested plants are along the edges of a crop, a perimeter spray is likely to control the majority of aphids. This approach will also preserve some of the beneficial invertebrates (see below) likely to be present in the crop.

Cowpea aphids favour legume hosts and are commonly found on faba beans, lentils, medic, lucerne, clover and lupins. They tolerate warm dry weather and can cause severe damage to moisture stressed plants. Dense colonies can deform leaves and growing points, and cause visible wilting. They also produce honeydew which can lead to the formation of a black sooty mould and reduce plant growth.

The cowpea aphid is easily distinguished from other crop aphids. To look at, adults are shiny black, up to 2 mm long and may have wings. Nymphs are smaller and dull grey in colour. All stages have white and black coloured legs. They often form dense colonies on a single plant before moving onto surrounding plants.  Click here for images of cowpea aphids.

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