Aphid activity update
Bluegreen aphids on lucerne
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Dalyup
Quenten Knight (Agronomy Focus) has reported a heavy infestation of bluegreen aphids causing widespread damage to a well-established lucerne crop at Dalyup. Quenten noted that there was a high population of beneficial insects in the crop. The lucerne crop will be heavily grazed to manage the aphid infestation.
Bluegreen aphids are most prominent during spring and can attack lupins, lucerne, chickpeas, faba beans, medics and clovers. Heavy infestations on the upper part of the plant can cause leaves to deform and plants to wilt and turn yellow.
Bluegreen aphid adults grow up to 3 mm long, are oval shaped, with long legs and antennae. They have 2 large cornicles that extend beyond the base of the abdomen. Both the winged and wingless forms are a matte bluish-green colour.
For more information refer to Cesar Australia’s Bluegreen aphid PestNote.
Canola aphids
Cabbage and turnip aphids
- Geraldton
- Northam
- South Stirlings
- Munglinup
There have been recent reports of cabbage aphid infestations in moisture stressed late flowering and early podding canola crops at Geraldton, Northam, Munglinup and South Stirlings.
Joel Kidd, Department of Primary Industries and Regional Development (DPIRD) Technical Officer has found cabbage aphids on racemes on 55% of plants inspected in a podding canola crop at Munglinup. In the same crop, Joel found green peach aphid (GPA) on the underside of leaves in 85% of plants inspected.
Daniel Malecki-Lee, DPIRD Technical Officer has found both cabbage aphids and turnip aphids on 30% of plants inspected in a late flowering/early podding canola near South Stirlings.
Back Paddock users have reported cabbage aphids in canola crops near Geraldton.
Amber Balfour-Cunningham, UWA Research Scientist found evidence of fungus and mummies on cabbage aphids in her late flowering/early podding canola trial at Northam. Amber observed that the cabbage aphids that had been present on canola racemes in previous weeks were now gone, even those found on plants at the edge of the crop.
It is common for multiple aphid species to colonise canola at the same time.
Cabbage and turnip aphids can cause significant yield loss to canola in spring through feeding damage, especially in areas where plants are already moisture stressed and aborting flowers or pods given the plant limitations. Aphid infestations in moisture-stressed canola crops that are in the fully podded stage can result in lower seed production. It can also result in the development of shrivelled seed due to aphids preventing seed fill.
Green peach aphid
- Binnu
- Tenindewa
- Geraldton
- Carnamah
Bill Campbell (Bill Campbell Consulting) reports high numbers of green peach aphid (GPA) on the undersides of leaves throughout a late flowering/pod ripening canola crop at Binnu. The crop is moisture stressed and leaf drop will not occur for a while.
Surya Dhakal, DPIRD Technical Officer has found GPA on the undersides of leaves in 85% of plants inspected in podding canola at Tenindewa, and on 70% of plants in podding canola at Carnamah.
Back Paddock users have also reported finding GPA in canola near Geraldton.
GPA feed on the underside of leaves and are not known to cause flower abortion.
DPIRD field trials in Geraldton have shown that GPA feeding damage to flowering canola did not cause yield loss. When aphids were introduced onto plants at the 8-10 leaf stage, and reached populations of 2,000 or more per leaf, in the absence of virus, they did not cause yield loss. For further information refer to DPIRD’s Canola yield loss to green peach aphid, Geraldton 2016 trial report.
DPIRD field trials at Katanning have shown that if GPA colonise canola at the seedling stage and are not controlled leading to more than 600 aphids on leaves by 10% flowering canola, plants will incur a yield loss. For further information on this trial refer to the GRDC Update Paper Yield loss to canola from green peach aphid.
Management of aphids
Seasonal conditions have been conducive for aphid numbers to build up and cause significant stress to already stressed plants. This can seriously reduce yields.
Threshold for control
Lupins
Failure to control aphid feeding damage can result in yield losses of up to 90% in susceptible varieties and up to 30% in varieties with intermediate resistance (in the absence of virus infection). Controlling aphids when they reach the threshold, which is 30% of flowering buds with 30 or more aphids, will give a yield response.
Canola
If more than 20% of canola 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 increases if canola crops are already under some degree of moisture stress or are experiencing poor finishing rains. If spraying is required, a border spray may suffice for cabbage aphids, which are most commonly found within 20 to 30 metres of the crop edge.
For a list of insecticides registered for use on aphids, see DPIRD’s 2024 Winter Spring Insecticide Guide.
Remember that naturally occurring parasitoids and predators such as hoverflies, wasps, lacewings and ladybird beetles will also increase with warming weather. These predators can keep aphid populations below threshold levels, and unnecessary spraying of 'anti-feed' synthetic pyrethroid sprays will only counteract their benefits.
When spraying, consider spray options that are soft on predators (for example, pirimicarb). Growers need to check canola crops for fungal infections and parasitism in aphids before deciding whether to invest in an insecticide spray. For more information, refer to the department’s Know what beneficials look like in your crop and Cesar Australia’s Beneficial’s chemical toxicity table page.
To read about prior canola aphid activity this season refer to DPIRD’s 2024 PestFacts WA articles in:
- Issue 9 Turnip yellows virus and green peach aphid detected in yellow sticky traps and canola crops
- Issue 6 Canola aphid and virus update
- Issue 4 Turnip yellows virus detected in migrating cabbage aphids.
For more information on diagnosing 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 Aphids in your crops YouTube video.
More information
For more information contact Svetlana Micic, Research Scientist in Albany on +61 8 9892 8591 or Dusty Severtson, Research Scientist in Northam on +61 8 9690 2160.
Article author: Bec Severtson (DPIRD Northam).