Insecticide resistance increasing in aphids
GroundCover™ Issue: 106 | Author: Sarah Clarry
Recent GRDC-funded research has uncovered widespread resistance among green peach aphid populations to pirimicarb, synthetic pyrethroids and organophosphates in Victoria, South Australia, New South Wales, Queensland and Western Australia.
Scientists, led by the research company cesar, have been investigating green peach aphid insecticide resistance in cropping regions over the past 12 months. The confirmation of widespread resistance to pirimicarb is particularly concerning for pulse and oilseed growers because this chemical has been a fallback for aphid populations resistant to other chemical groups.
Pirimicarb is aphid-specific and less harmful to other invertebrates when applied to crops, so is compatible with an integrated pest management (IPM) approach.
In 2010, the first documented case of resistance to pirimicarb in Australia was identified in a green peach aphid population from WA.
This was the first confirmed instance of green peach aphid resistance to carbamates in Australia, although tolerance to pirimicarb was identified some years previously by state agricultural entomologists in WA and in other states.
The current research team screened 36 populations over an area spanning more than 1700 kilometres across eastern Australia and an area of 800km in WA.
Dr Paul Umina of cesar says that of the 27 populations tested in eastern Australia, 13 showed high resistance to synthetic pyrethroids, indicating resistance to this chemical group has become more common over the past five to 10 years.
Organophosphate resistance, observed in Australia for many years, has also been identified in populations across all states.
“Most alarming was the discovery that 11 populations in eastern Australia were resistant to pirimicarb,” he says.
Green peach aphid resistance to insecticides has been known overseas for some time, but the widespread resurgence of resistance to all three chemistries is something that has increased only recently.
Dr Umina says the levels of resistance identified were far greater than what was anticipated. “In some populations, aphids exhibited more than 10,000 times the resistance to synthetic pyrethroids than the control populations.”
In WA, pirimicarb resistance has been found to be widespread across vegetable-growing areas in the south west.
Department of Agriculture and Food, WA (DAFWA), PestFax coordinator Peter Mangano says grain growers have experienced significant issues with resistance in green peach aphid this season.
There have been almost 20 reported chemical control failures involving green peach aphid across the year, mostly in seedling and establishing canola crops.
Mr Mangano says green peach aphid damage has been most noticeable in isolated patches within crops where high densities of the aphids have been found on the undersides of leaves.
These patches have generally increased in size with time, resulting in thinned and stunted plant growth and in many cases bare patches within crops. Monitoring green peach aphid populations and reducing ‘insurance sprays’ will help to prolong the lifespan of insecticides used to control green peach aphid.
The next research steps will be to understand if individual aphids have resistance to all three chemistries and to explore the genetic makeup of green peach aphid populations.
Dr Umina says: “If we discover that individual aphids have resistance to organophosphates, synthetic pyrethroids and carbamates, it will mean the likely reproduction of fully resistant offspring, as green peach aphids can reproduce asexually to produce clones of themselves. This will have significant implications for the ability of growers to control green peach aphid in crops.”
The work, conducted in conjunction with CSIRO, the South Australian Research and Development Institute, the NSW Department of Primary Industries, the Department of Agriculture, Fisheries and Forestry Queensland and DAFWA, is screening other species of crop aphids as well.
Monitor and report
Growers are encouraged to keep an eye out for any control difficulties when applying chemicals as per label instructions, and to rotate insecticide classes to prevent resistance from developing further.
If you have crop aphids that survive registered rates of pesticide treatments or suspect that you have resistant green peach aphids, contact Dr Paul Umina or CSIRO’s Dr Owain Edwards.
Dr Paul Umina
03 9349 4723,
Dr Owain Edwards
08 9333 6401,
GRDC Project Code CES00001
Region North, West, South