Green light for redlegged earth mite pesticide resistance test

A screening service to test for insecticide resistance in redlegged earth mite (RLEM) is again being made available to grain growers and their advisers in 2017, thanks to the Grains Research and Development Corporation (GRDC).

Through a GRDC investment, cesar is screening RLEM populations across South Australia, Victoria, Tasmania and southern New South Wales.

Dr James Maino from cesar says growers and advisers suspecting a chemical control failure against RLEM are encouraged to contact cesar to access the service that is available at no extra cost to growers through a national GRDC investment led by the University of Melbourne, in collaboration with cesar, the Department of Agriculture and Food Western Australia and CSIRO.

“The service will help to identify the best control options for growers, and detect any resistance before it becomes more widespread,” Dr Maino says.

Earlier in 2017, resistance was confirmed in multiple RLEM populations from SA to both synthetic pyrethroids (SPs) and organophosphates (OPs). This was the first detection outside of Western Australia where many RLEM populations have shown high levels of insecticide resistance for more than a decade.

“Further sampling will enable more detailed mapping of the extent of resistance in the southern and northern cropping regions,” Dr Maino says.

RLEM is a threat to the profitability of a range of Australian crops and pastures, with canola, lupins and legume seedlings the most susceptible to attack. Mite feeding can lead to distortion or shrivelling of leaves and affected seedlings may die at emergence when mite populations are high.

There are few options available to growers for control of RLEM and resistance to OPs and SPs will only increase the dependence on the remaining major chemical group of neonicotinoids. Although limited in options, experts say it is still crucial to minimise chemical use and rotate chemical groups to curb the spread of insecticide resistance.

To guide growers and their advisers in their efforts to control RLEM and reduce the risk of resistance occurring, a Resistance Management Strategy (RMS) for SA, Tasmania, Victoria and southern NSW has been developed (in addition to a separate strategy for WA).

The RMS for the Redlegged Earth Mites in Australian Grains and Pastures, developed through the National Insecticide Resistance Management (NIRM) working group and endorsed by CropLife Australia, has been published by the GRDC and is available for viewing and downloading on the GRDC website.

Source: GRDC