Green light for RLEM pesticide resistance test

Through a GRDC investment, cesar is screening RLEM populations across SA, Vic, Tas and southern NSW.

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.

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

Earlier this year, resistance was confirmed in multiple RLEM populations from SA to both synthetic pyrethroids and organophosphates.

This was the first detection outside of WA, where many RLEM populations have shown high levels of insecticide resistance for more than a decade.  

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

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 for SA, Tas, Vic and southern NSW has been developed.

The RMS for the Redlegged Earth Mites in Australian Grains and Pastures, developed through the National Insecticide Resistance Managementworking group and endorsed by CropLife Australia, has been published by the GRDC on its website.