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Cowpea aphids

Consultant, Simon Mock (Clovercrest Consulting), has reported cowpea aphids (Aphis craccivora) in a faba bean crop and several seedling lucerne crops near Bordertown, in SA. The aphids are causing minimal feeding damage, although some lucerne paddocks may be sprayed where numbers are high and crops are water-stressed. There have been reports of cowpea aphids on lentil crops, near Kaniva, in the Wimmera district of Victoria. Approximately 10-20 aphids are present per plant, although the feeding damage is reported to be low. Agronomist, Kate McCormick (John Stuchbery and Associates), also reports that cowpea aphids have been seen on several crops in the Wimmera district of Victoria.

The cowpea aphid is easily distinguished from other crop aphids. To look at, adults are shiny black and nymphs are dull grey in colour. All stages have white and black coloured legs. Winged adults move into crops where they reproduce and colonise on the growing tips of host plants. Mild winter conditions can result in the establishment of many small aphid colonies throughout a crop.

Cowpea aphids favour legume hosts and are commonly found on faba bean, lentil, medic, lucerne, clover and lupins. They tolerate warm dry weather and can cause severe damage to water stressed plants. Aphid numbers fluctuate greatly with weather conditions and are difficult to predict. They tend to arrive in pulse crops earlier than other aphid species.

Direct feeding damage from aphids occurs when clusters of about 30 or more individuals develop on individual growing tips. The degree of damage depends on the varietal susceptibility, the growth stage of the crop, the percentage of plants infested and the duration of the infestation.

For images of cowpea aphids, click here.

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