Farm Management

Insecticide preservation central to WA RLEM strategy

RLEM feeding can lead to distortion or shrivelling of plant leaves and affected seedlings may die where there are high populations present.

A resistance management strategy targetted at Western Australian growers aims to conserve the effectiveness of the limited insecticide options available for controlling redlegged earth mites in grain crops and pastures.

It is one of two regionally relevant strategies developed by the National Insecticide Resistance Management (NIRM), working group of the Grains Pest Advisory Committee (GPAC), and endorsed by CropLife Australia.

GPAC is a Grains Research and Development Corporation (GRDC)-funded project which provides strategic advice on pest issues.

RLEM (Halotydeus destructor) is a major threat to a variety of Australian crops and pastures, with canola, lupins, and legume seedlings the most susceptible to attack.

Western Australian Department of Agriculture and Food (DAFWA) entomologist Svetlana Micic said high levels of resistance to synthetic pyrethroids (SPs), including bifenthrin and alpha-cypermethrin, were becoming more common across the WA grainbelt.

“In addition, localised resistance to organophosphates (OPs), including omethoate and chlorpyrifos, has been discovered on multiple WA properties,” Ms Micic said.

NIRM chairman and entomologist Paul Umina, of cesar, said growers needed to understand how to minimise the development of resistance, and encouraged them to adopt the recommendations of the Resistance Management Strategy which would help guide their selection of control options.

He said the rotation of different chemical groups was central to the strategy and would minimise the selection pressure for resistance to the same insecticide group across consecutive generations of RLEM.

“Do not use the same chemical group across successive spray windows (on multiple generations of RLEM) as this will select for resistance to that chemical group,” Dr Umina said.

“In addition it is recommended that co-formulations or chemical mixtures are best reserved for situations where damaging levels of RLEM and other pest species are present, and a single active ingredient is unlikely to provide adequate control.”

Dr Umina said growers should at all costs avoid the practice of ‘insurance’ sprays and advised that using the broadest range of integrated pest management (IPM) strategies was the best way to avoid future spray failures, and prevent or delay the development of insecticide resistance.

Growers who find RLEM that survive registered rates of insecticide treatments in 2018 can arrange for resistance testing to be conducted by contacting Ms Micic on, 08 9892 8591, or 0427 772 051.

The Resistance Management Strategy for the Redlegged Earth Mite in Australian grains and pastures – western region – is available as a GRDC Fact Sheet at

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