Green peach aphid insecticide resistance causes concern
Northern region grain growers are being encouraged to put in place insecticide resistance management strategies compatible with the long-term management of green peach aphid (GPA).
Studies funded by the Grains Research and Development Corporation (GRDC) have found that the extent of insecticide resistance in GPA populations across Australia has escalated.
With widespread resistance to synthetic pyrethroids, carbamates and organophosphates existing in Australia’s mainland cropping regions, insect pest management experts say rotating chemical groups and taking advantage of biological control are essential to extend the useful life of available chemistries.
They say heavy reliance on insecticides to manage aphid populations places strong selection pressure on the insect to develop resistance, leaving growers with limited future control options.
GPA is not considered a major pest of canola or pulse crops in the northern region but is known to be present in these crops at sub-threshold levels, according to Department of Agriculture, Fisheries and Forestry (DAFF) Principal Entomologist Dr Melina Miles.
“Consequently, it is important that growers are aware of the risk of increasing the prominence of this pest through the use of insecticides to which it is resistant,” Dr Miles said.
GPA is a major pest of several horticultural commodities and can transmit more than 100 plant viruses such as beet western yellows virus (BWYV) and cucumber mosaic virus (CMV). A combination of BWYV and aphid damage early in the life of a canola crop can cause yield losses of up to 50 per cent.
Research led by science-based company cesar has been investigating GPA insecticide resistance in cropping regions over the past two years and the findings and implications for growers are outlined in a new GRDC Fact Sheet, Resistance Management for Green Peach Aphid.
Dr Paul Umina, of cesar, says resistance to synthetic pyrethroid insecticides has become significantly more common over the past 10 years. Organophosphate resistance has also been identified in many field populations across all states.
“More alarming was the discovery that more than half of all populations surveyed across Australia were resistant to the carbamate, pirimicarb,” Dr Umina said.
“At the population level, we have identified resistance to all three chemical groups – synthetic pyrethroids, carbamates and organophosphates. GPA resistance to insecticides has been known overseas for some time, however the widespread resistance to all three chemistries is something that has only been observed recently in Australia.”
Dr Umina said the levels of resistance identified were far greater than what was anticipated.
The confirmation of widespread resistance to pirimicarb was particularly concerning for pulse and oilseed growers as this chemical is widely used because it is aphid-specific and less harmful to other invertebrates, and therefore compatible with an integrated pest management (IPM) approach.
Within Australia, GPA primarily reproduce asexually to produce clones of themselves and recent studies have shown that individual clones contain resistance to multiple chemical groups. This unfortunately means that controlling these populations will be difficult with chemicals, even if rotating between different chemical groups.
Western Australian-based CSIRO research scientist Dr Owain Edwards says it is likely that GPA has developed resistance to more insecticides than any other insect species, not only in Australia but throughout the world.
Dr Edwards said that since he was involved in a GRDC-funded national survey of GPA in the mid-2000s, the increase in insecticide resistance in Australian populations had grown at a significant rate.
“With the resistance profile we now have, controlling GPA in years of high infestation can be difficult,” Dr Edwards said.
“Problem years for GPA tend to be associated with an abundant ‘green bridge’ over summer, so it is important to eliminate weeds and volunteer crops growing during the period between harvest and sowing.”
Growers are advised to implement GPA insecticide resistance management strategies, as outlined in the new Fact Sheet, including:
- Avoiding the use of cheap, broad-spectrum ‘insurance’ sprays
- Applying insecticides only after correctly identifying pest species and monitoring to determine the likelihood of crop loss
- Rotating insecticides from different chemical groups
- Considering the selection pressure on GPA of using synthetic pyrethroids, carbamates and organophosphates to control other pests early season
- Incorporating non-chemical control methods and encouraging beneficial insect activity by using ‘softer’ chemicals and biopesticides.
The Fact Sheet can be viewed and downloaded via www.grdc.com.au/GRDC-FS-GreenPeachAphid.
Caption: Studies funded by the GRDC have found that the extent of insecticide resistance in GPA populations across Australia has escalated. Photo: Andrew Weeks
Elise McKinna, DAFF Media & Communication Officer
07 3087 8576
Paul Umina, cesar
03 9349 4723
Owain Edwards, CSIRO
08 9333 6401
Sarah Jeffrey, Senior Consultant Cox Inall Communications
GRDC Project Code CES00001