Cabbage aphid

Description

Cabbage aphid nymphs are bright green before turning a dull grey-green colour that is up to 3 mm long and they can be winged or wingless. They are often found on the underside of leaves and as they usually invade crops from the crop edge, these plants often show the first signs of infestation.

In horticultural brassica crops, cabbage aphids form large colonies on the youngest leaves, causing them to become stunted and distorted. These colonies can also become a contamination issue at harvest. 

In canola, cabbage aphids form grey colonies covered in a thick grey covering on the flowering spikes of canola.

Control

Controlling brassica weed hosts, such as wild radish and turnip, between seasons will help reduce aphid pressure. In broadacre, sowing canola into standing stubbles also helps to reduce aphid landings.

Cabbage aphid populations peak in late winter and early spring. At this time, beneficial insects can play an important role in suppressing aphid populations, so it is important to consider beneficial insect populations when assessing aphid spray thresholds as well as the impact of the product applied.

In addition to beneficial insect numbers, consider the current growing conditions. If crops have good growing conditions at the time of infestation (i.e. good soil moisture), they are more likely to be able to compensate for aphid damage compared to moisture stressed plants.

Movento® is soft on many beneficial insects, including parasitic wasps, pirate bugs, hoverflies and lacewings. It is registered for the control of cabbage aphid in brassica vegetables (i.e. broccoli) and brassica leafy vegetables (i.e. bok choy). Confidor® is also registered for the control of grey cabbage aphid in brassicas.

References

Cesar (Viewed September 2019), ‘PestNotes, Southern : Cabbage aphid), http://cesaraustralia.com/sustainable-agriculture/pestnotes/insect/Cabbage-aphid