Aphids are active
Research agronomist Carla Milazzo (DPIRD) has reported finding cabbage and turnip aphids on roadside volunteer canola near Kendenup.
Quenten Knight (Agronomy Focus) has found low levels of winged aphids and some nymphs in 4-6 leaf canola at Beaumont. The aphid species are unknown but were found in growing buds and the underside of canola leaves.
Three aphid species commonly attack canola in Western Australia: cabbage aphid, turnip aphid and green peach aphid (GPA).
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 usually first appear as 'hotspots' along the edge of crops in the paddock. The adult aphid is dull or greyish-green. GRDC recently released a Managing cabbage aphid video.
Turnip aphids infest canola crops in a similar way to cabbage aphids, usually first appearing along crop edges. Turnip aphid colonies establish around growing tips and flowering spikes and often establish in 'hotspots' in the paddock. Aphids have a light waxy coating, which is not as pronounced as the powdery cover of the cabbage aphid. Adults are olive to greyish green, usually with dark bars on the abdomen.
Turnip and cabbage aphids are the two aphids species which commonly infest mid to late-season canola, while green peach aphids are more common early in the season.
Green peach aphids (GPA) occur on the underside of canola leaves of young plants and tend to be more evenly distributed in the paddock. The GPA varies in colour from shiny pale yellow-green to mid-green, orange or pink.
GPA is an important vector of a number of plant viruses including turnip yellows virus (TuYV), cauliflower mosaic virus (CaMV), turnip mosaic virus (TuMV) and cucumber mosaic virus (CMV), all of which damage canola.
Managing canola aphids
Crops early in the season tend to outgrow aphid damage particularly if there are good growing conditions. The cooler the weather the slower the lifecycle of the aphid and the less offspring they produce.
Identify the canola aphids in the crop early.
If you do identify GPA in your crop, monitor and only spray if seedling crops are moisture stressed and/or have high numbers of GPA on the plant so the plant is unable to outgrow GPA feeding damage.
Aphid activity will slow down if cold and wet weather conditions are experienced.
Australian GPA populations are known to have resistance to four different chemical groups – synthetic pyrethroids (for example, alpha-cypermethrin), organophosphates (for example, dimethoate), carbamates (for example, pirimicarb) and neonicotinoids. Recently evidence of the green peach aphid (Myzus persicae, GPA) developing metabolic resistance to sulfoxaflor (Transform™) has been confirmed for the first time in Australia, after a small number of aphid populations from Esperance were shown to have reduced sensitivity to the insecticide. For more information see the 2019 PestFax Issue 5 article First signs of low-level resistance evolving to Transform™ detected in isolated WA green peach aphid populations .
To limit the spread and curb the further evolution of resistance, it is critical that sulfoxaflor (Transform®) is used judiciously and as part of a sound insecticide resistance management strategy. For more information refer to GRDC’s Resistance Management Strategy for the Green Peach Aphid in Australia Grains.
Growers are asked to keep a close eye on establishing canola crops this year and to contact Dr Paul Umina (cesar) on +61 (0)3 9349 4723 if aphids survive a Transform™ application.
Pirimicarb and sulfoxaflor are currently registered for aphid control in canola crops in WA.
Yield loss from cabbage and turnip aphids, is more likely to occur when flowering spikes are colonised. If more than 20% of plants are infested with colonies of canola aphids, control measures should be considered to avoid yield losses
For more insecticide information refer to DPIRD’s 2019 Winter Spring Insecticide Guide.
For more information on identifying and managing canola aphids see DPIRD’s;
- Aphid management in canola crops page
- Diagnosing canola aphids page
- 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children
- Aphids in your crops YouTube video.
Article authors: Cindy Webster (DPIRD Narrogin) and Svetlana Micic (DPIRD Albany).