Identifying aphids in canola

Distinguishing aphid species in canola is not always immediately obvious. So, what are some features to look for when identifying these aphids in the field? 

 

Green peach aphid (Myzus persicae, GPA), cabbage aphid (Brevicoryne brassicae), and turnip aphid (Lipaphis pseudobrassicae), are the three main culprits that feed on and transmit viruses in canola in south-eastern Australia. It’s important to distinguish between these species as unlike cabbage and turnip aphid, GPA has evolved resistance to major chemical groups.

It’s not uncommon for multiple species to be present in the one crop. Green peach aphid can go under the radar amongst turnip aphid or cabbage aphid which can lead to costly control failures due to incorrect insecticide selection. For example, pirimicarb will control cabbage aphid and turnip aphid but will not kill GPA (even at high rates).

Colonisation habits and appearance are two areas that can assist with identification.

Turnip aphid and cabbage aphid are known for their tendency to colonise upper leaves and form clusters on canola flowering spikes in spring. Green peach aphid, however, prefers to inhabit the lower leaves and are more sparsely distributed.

These habits aren’t always so obvious, such as in young canola, under a very high aphid pressure, or in spring-sown and early sown canola crops. This is where morphological traits can help.

Cabbage aphid colonies have a characteristic blue-grey appearance and are normally covered in a whitish powder. Turnip aphid colonies are typically olive to greyish-green and covered with a white wax, although this is not as obvious as that on the cabbage aphid. Sometimes dark bars are visible on the abdomen of the turnip aphid and cabbage aphid.

Green peach aphid varies in colour from shiny pale yellow-green, green, orange or pink. If looked at closely with a hand lens, GPA has a shimmery appearance.

Multiple aphid species on canola. Note the white film and dark marking on the abdomen of the cabbage aphid (top) and the shimmering appearance of the pink coloured green peach aphid (bottom) (Source: cesar). 

Turnip aphid adult. Note the fine white wax and olive-green colour (Source: cesar). 

 

For more information on canola aphids, visit the following PestNotes:

Green peach aphid

Cabbage aphid

Turnip aphid

 

Field reports of canola aphids

Tim Condon – Delta Agribusiness (South West Slopes, NSW)

Adam Dellwo – Elders (Riverina, NSW)

Ben Lenehan – Delta Agribusiness (Southern Tablelands/South West Slopes, NSW)