Earth mites face testing times with new resistance screen

Author: Sharon Watt | Date: 29 May 2014

Close-up of red-legged earth mites on a leaf

Grain growers in the southern cropping region can now access a new testing service to determine if insecticide resistance exists within populations of redlegged earth mite (RLEM) on their properties.

A new high throughput, DNA-based test for resistance in RLEM has been developed through a Grains Research and Development Corporation-funded research project that is investigating the mechanisms responsible for resistance to synthetic pyrethroids (SPs) in this important crop pest.

This collaborative work, led by the University of Melbourne and involving cesar, CSIRO, the Department of Agriculture and Food Western Australia (DAFWA) and the University of Western Australia, has led to establishment of the test which will be used to screen RLEM populations in WA, South Australia, Victoria, New South Wales and Tasmania during the 2014 and 2015 winter cropping seasons.

Project leader, Dr Paul Umina, says identification of the gene mutation responsible for pyrethroid resistance has enabled researchers at CSIRO to devise a new cost-effective DNA test which requires fewer mite numbers per test and has greater population screening capacity than previous testing services.

“It now costs far less to carry out resistance testing with far fewer mites needed, and the laboratory tests can be undertaken on stored samples of mites at any time of the year,” Dr Umina said.

“Available to growers and advisers through a GRDC-funded program, the service provides an opportunity for growers to know what is happening in their paddocks in terms of insecticide resistance.”

Dr Umina said RLEM resistance to pyrethroids had been confirmed on 30 separate properties in WA, with a distribution that is widespread across the state’s wheat belt.

“Resistance has occurred on WA properties that are more than 1000 kilometres apart, so while we don’t anticipate uncovering resistance in other states just yet, we do know that the likelihood of resistance developing elsewhere is very strong,” Dr Umina said.

The laboratory-based DNA test is undertaken by CSIRO. To discuss suspected resistance and to facilitate collection of samples for testing, growers in SA, Victoria, NSW and Tasmania are encouraged to contact Paul Umina of the University of Melbourne (phone 03 9349 4723, email in the first instance.

“We are keen to hear from growers across the southern who experience difficulties controlling earth mites with chemicals and/or suspect insecticide resistance on their property. All resistance testing results will remain confidential, and key management recommendations will be provided to growers on a case-by-case basis,” Dr Umina said.

The resistance testing service is part of a three-year GRDC-funded investigation into resistance in RLEM, which is expected to lead to recommendations about insecticide resistance management and improved chemical control methods. A key component of the work will be the integration of field surveillance, population genetics research and mite fitness studies into an improved set of management tools.

Better understanding of RLEM biology will be used to develop recommendations for long-term management and monitoring guidelines to be implemented across the southern and western cropping regions.


Caption: Grain growers can access a new testing service to determine if insecticide resistance exists within populations of redlegged earth mites on their properties. Photo: A Weeks, cesar.

More information

For Interviews

Dr Paul Umina, the University of Melbourne
03 9349 4723 


Sharon Watt, Porter Novelli
0409 675100

GRDC Project Code UM00049

Region South, North