Cost of insurance sprays

31 Jul, 2012 02:00 AM

With insecticide resistance increasing in the insect population of the northern cropping region, researchers are urging growers to take a closer look at integrated pest management (IPM) and avoid ‘insurance’ sprays.

The Grains Research and Development Corporation (GRDC) has produced a new six-page publication containing the latest guidelines to reducing reliance on insecticides, limiting the opportunity for resistance and promoting populations of beneficial species.

Insecticide Resistance Management and Invertebrate Pest Identification highlights the research recommendations of GRDC-supported work led by Hugh Brier and Dr Melina Miles of the Queensland Department of Agriculture, Fisheries and Forestry (DAFF).

Dr Miles said long term reliance on broad spectrum insecticides for invertebrate pest control is not sustainable.

“Sustainable insect pest management is underpinned by correct pest identification, crop monitoring, economic thresholds and the use of selective insecticides where possible,” she said.

“Prophylactic or ‘insurance’ sprays can speed up the development of resistant pest populations.”

Dr Miles said beneficial insects could make a valuable contribution to the suppression of many key pests and implementing IPM improved economic, environment and social outcomes.

The GRDC Fact Sheet outlines four key points for implementing IPM, including: recognise your insects; know the control thresholds for your crops; monitor insect populations and select appropriate control methods.

A detailed table guides growers on what to check for and when. It outlines pest risks at the four stages of crop growth including crop establishment, vegetative stage, flowering and pod/seed set and grain fill.

Dr Miles said repeated exposure of pests to sub-lethal doses of insecticides hastens the selection for resistance in pest populations.

“Surviving pests carry genes that confer insecticide resistance and repeated insecticide applications increase the proportion of resistant individuals until the major are resistant,” she said.

“In the northern region, Helicoverpa armigera has developed resistance to most older insecticide groups.

“This means the allowable number of sprays per crop of many newer insecticides is restricted to reduce the risk of further resistance developing in this major pest.”

Dr Miles said any IPM measure that reduced the need to spray for helicoverpa also reduced the risk of it developing resistance to newer, more IPM-compatible insecticides.

Other northern grain pests with pesticide resistance issues include redbranded shield bug, bean podborer and spider mites.

* For more information on managing insecticide resistance or to download the GRDC Fact Sheet, visit



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