There are a number of canola crops in this season, and as the weather warms up the aphid numbers are building up in some of them. The aphids that colonise canola are most commonly the cabbage and the turnip aphid. There may also be a few green peach aphid present.
The aphids colonise the terminal end of the flower spike (raceme). Early infestations can be difficult to see in amongst the buds. As the populations grow, they can expand down the stem causing the raceme to distort.
A. Cabbage aphid B. Green peach aphid. Ci and Cii. Turnip aphid (photo: DAFWA)
The threshold for aphids in canola, developed in WA, is: 20% of plants infested with aphids.
Aphid infestations are typically patchy, and often heavier on crop edges. Ensure that crop sampling covers a representative area of the crop, with a minimum of 20 plants examined at 2-3 locations within the crop.
For more information on the management of aphids and other pests in canola go to the following links.