sustainability through science & innovation

Canola aphids causing havoc

With the recent warm, dry conditions, aphids have become a major problem in canola crops across many parts of Victoria and southern New South Wales. Two main species that are commonly found in canola are the cabbage aphid (Brevicoryne brassicae) and the turnip aphid (Lipaphis erysimi), which both form dense colonies around the flowering tips. A third species, the green peach aphid (Myzus persicae), also attacks canola however they are generally a pest to a lesser extent, and are usually found scattered on the undersides of leaves.

Agronomist, Chris Duff (Delta Agribusiness), has reported finding high numbers of cabbage aphids in canola crops across much of southern New South Wales. Chris says numbers have increased significantly over the past fortnight with numbers building-up earlier this year than in previous years. Chris says he has noticed aphids tend to be a greater problem in dry years, and says this season is one of the highest infestations he has seen in the past 20 years. 

Cabbage aphids have also been reported by agronomist, Tim Paramore (Tim Paramore Agronomic Services), in canola crops between Albury and Corowa, in the Riverina district of New South Wales. Tim says aphids are widespread in canola throughout this region and he has noticed a huge increase in numbers over the last week. Until recently, the aphids were only present in high numbers around the perimeters of crops, however they are now well above threshold levels well into most paddocks. Tim says that whilst most crops are close to windrowing, many growers are still considering chemical control due to the high levels of infestation. Agronomist, Jan Edwards (NSW DPI), says aphids are threatening canola crops around Young and Cowra (in the South West Slopes district), and in parts the Riverina district, New South Wales. Jan says the aphids could wreak havoc on moisture-stressed crops by sucking the sap from the stems.

Technical Specialist, Don McCaffrey (NSW DPI), says aphids are a major problem in canola crops across the South West Slopes district of New South Wales. Parts of some crops are completely covered with aphids from top to bottom and some plants have been totally destroyed. Don says this is one of the worst years he has seen for aphids on a state-wide basis, and estimates that 70% of canola crops across New South Wales will be sprayed to control aphids this season.

Researcher, Stuart McColl (cesar), reports finding aphids in several canola crops around Elmore, in the Northern Country district of Victoria. In one crop, Stuart has observed cabbage aphids, turnip aphids and green peach aphids, and says all three species appear to have increased in numbers in the past few weeks.

The three main aphid species which attack canola can be distinguished by the following:

  • Cabbage aphids grow up to 3 mm in length and have a dull grey-green coloured body. Under favourable conditions, dense colonies form, which appear bluish-grey and are covered with a fine, whitish powder.  Click here for images of cabbage aphids.
  • Turnip aphids are olive to greyish green in colour with dark bands on the abdomen. They have a light covering of wax and also form dense colonies.  Click here for images of turnip aphids.
  • Green peach aphids have an oval shape body and may be pale yellow-green, orange or pink in colour. Winged adults have a dark patch on the abdomen. Unlike the other two species, green peach aphids are usually sparsely distributed within a crop, mainly on the underside of leaves. Some populations are resistant to insecticides.  Click here for images of green peach aphids. 

In response to the serious aphid problem that has arisen this season and the lack of pirimicarb (e.g. Aphidex®, Atlas®, Pirimor®) available to growers in many regions, the APVMA has issued an emergency use permit for controlling aphids in canola crops grown in New South Wales. This permit allows the use of dimethoate to control green peach aphids and cabbage aphids, and is valid from 15th October 2008 until 31st March 2009. Importantly, the permit states a withholding period of 21 days, which applies to the time of windrowing or direct heading. Additionally, canola crops sprayed with dimethoate cannot be grazed or cut for fodder. To view a copy of the emergency use permit click here.

For further information on aphid management in canola crops, click here.

PestFacts is supported by