Cabbage, turnip and bluegreen aphids
Cabbage and turnip aphids
- Grass Valley
Entomologist Dusty Severtson (DPIRD) has recently found small numbers of cabbage aphids on the edge of a canola crop near Grass Valley. The crop was at the early flowering stage and a few isolated plants on the crop edge were infested.
Dusty has also reported finding hot spots, mostly along crop edges, in late flowering canola crops near Amelup. Parasitised mummies were also present in one crop indicating beneficial insect activity. One crop in the area had a mixture of cabbage and turnip aphids on racemes.
Growers and consultants are advised to re-check canola crops for aphids, even if they have been previously sprayed, especially if the crop has experienced frost. They also need to check canola crops for fungal infections and parasitisation in aphids before deciding to invest in an insecticide spray. For more information see the department’s Know what beneficials look like in your crop.
Cabbage aphids form dense bluish grey colonies covered with fine whitish powder on flowering heads in spring. They also establish on crowns and under leaves in the vegetative phase. Infestations are usually as ‘edge effects’ or 'hotspots' in the paddock. The adult aphid is dull or greyish-green.
Cabbage aphids can feed on canola plants, particularly if warm daytime temperatures are experienced which favour aphid reproduction and feeding damage.
If more than 20% of plants are infested with colonies of cabbage or turnip aphids, control measures should be considered to avoid yield losses. The risk of economic yield losses to aphids is increased if canola crops are already under some degree of moisture stress or experience poor finishing rains.
Growers, consultants and other field operators that would like to know how close they are to the canola aphid threshold and where across crops this is occurring can download the new CropScout app. The app is designed to assist inspection of canola for aphids relative to the spray threshold and easily record and visualise results on a map. This field intelligence can then be used to optimise spray timing and, where possible, to target sprays to pest infestations across properties or within individual crops. For more information, see the department’s CropScout page.
For a list of insecticides registered for use on aphids see the department’s 2019 Winter/Spring Insecticide Guide.
For more information on identifying and managing canola aphids refer to;
- DPIRD’s Aphid management in canola crops page
- DPIRD’s Diagnosing canola aphids page
- DPIRD’s 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children
- GRDC’s Managing cabbage aphids YouTube video.
Brent Pritchard (Farmanco) has found aphids likely to be bluegreen aphids starting to colonise lucerne seedlings in the Borden area. The crop is being monitored.
Entomologist Dusty Severtson (DPIRD) has found very high numbers of bluegreen aphids on lucerne at Amelup. They were found on the underside of leaves and were not noticeable unless plants were knocked onto a hand or container.
Bluegreen aphid adults grow up to 3 mm long, are oval shaped, with long legs and antennae. They have two large cornicles that extend beyond the base of the abdomen. Both the winged and wingless forms are a matte bluish-green colour. Nymphs are similar to adults but are smaller in size.
Bluegreen aphids are active during autumn and winter but are most prominent during spring.
Bluegreen aphids feed on the upper leaves, stems and terminal buds of host plants.
For more information refer to cesar’s Bluegreen aphid PestNote.
For more aphid information contact Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160 or Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758 or Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591.
Article authors: Cindy Webster (DPIRD Narrogin), Dusty Severtson (DPIRD Northam), Alan Lord (DPIRD South Perth).