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Free screening service to test for insecticide resistance in the redlegged earth mite

03 June 2021

Redlegged earth mite (RLEM) is a pest affecting crops and pastures across southern Australia.  Insecticides are currently the most effective and widely used control method against RLEM, however the emergence and spread of insecticide resistance to synthetic pyrethroids (SPs) and organophosphates (OPs) in the RLEM has resulted in a need for a reassessment of management options for this pest.

Meat and Livestock Australia (MLA) is co-investing into a Grains Research and Development Corporation (GRDC) project led by Cesar Australia to reduce the significant impacts of RLEM to grain and pasture productivity through improved pest management.

The work will lead to improved biological, cultural, and chemical control strategies for RLEM, as well as resistance management recommendations to maintain effectiveness of current chemical control options.

As part of this research, Cesar Australia is running a free screening service to test for insecticide resistance in RLEM.

Producers and advisors who have noticed a chemical control failure, suspect insecticide resistance or have paddocks that continually require control of RLEM with pesticides are asked to contribute to this important research by getting in touch.

This no-cost screening service is made possible through a GRDC investment and MLA co-investment being led by Cesar Australia in collaboration with the University of Melbourne, the Western Australian Department of Primary Industries and Regional Development and CSIRO.

Associate Professor Paul Umina, director of Cesar Australia, says a major concern facing Australian grain and pasture growers is the heavy reliance on only three registered chemical classes to control RLEM – neonicotinoids as a seed dressing, and synthetic pyrethroids (SPs) and organophosphates (OPs) as foliar insecticides.

“Insecticide resistance in RLEM to both SPs and OPs had previously only been detected in Western Australian populations but since 2016 has been confirmed in multiple populations from South Australia and in Victoria,” Assoc. Prof.  Umina says.

Cesar Australia is actively screening populations from South Australia, Victoria, New South Wales and Tasmania where control failures or suspected resistance to SPs and/or OPs may be occurring.

The research team are interested in hearing from growers or advisers who have experienced recent or past chemical control failures or have paddocks that continually require control of RLEM with pesticides.

“RLEM populations from paddocks which are frequently impacted by the mites, and often require spraying, are ideal candidates for resistance testing,” Assoc. Prof. Umina says.

Cesar Australia will be undertaking field trips to collect RLEM for resistance screening, so get in touch if you would like them to collect RLEM from your area.

Although insecticide options are limited, Assoc. Prof. Umina says it is still crucial to minimise chemical use and rotate chemical groups to curb the spread of insecticide resistance.

He says the screening service will not only help detect any resistance before it becomes widespread but will also assist in identifying the best control options for growers.

“We encourage growers and advisers to make use of this service, and also refer to the National RLEM Resistance Management Strategy to help avoid control failures.”

The RLEM Resistance Management Strategy can be found on the GRDC website at, as well as the IPM Guidelines for Grains website at

For Interviews

Dr James Maino, Cesar Australia
Phone 0400 150 564

For further information about the resistance testing service

Dr Aston Arthur, Cesar Australia
Phone 0427 875 040