Western Australia
December 8, 2015
Broadacre producers preparing pest control measures for next season have been urged to consider a more strategic response, after redlegged earth mite (RLEM) resistance to the insecticide chlorpyrifos was recently confirmed in the South West.
The discovery was made by the Department of Agriculture and Food, as part of a national research project supported by the Grains Research and Development Corporation, in co-operation with the University of Melbourne, cesar, CSIRO and the University of Western Australia.
Department research officer Svetlana Micic told a recent Crop Protection Forum that although RLEM resistance to chlorpyrifos, an organophosphate, had been discovered on just two properties it could, in time, spread to the Wheatbelt.
Ms Micic said the occurrences were an important wake-up call for landholders to prepare for resistance by implementing integrated pest management strategies to minimise the risk to broadacre pastures and crops.
“With less chemical groups to rely on, it is important not to use a blanket, ‘one size fits all’ response and to use alternative chemicals, if possible, alongside cultural control practises,” she said.
RLEM populations individually resistant to synthetic pyrethroids (SP) or to the organophosphate (OP) omethoate have previously been confirmed in broadace crops.
In 2014 RLEM populations with cross-resistance to omethoate and synthetic pyrethroids were also detected.
Ms Micic said to prolong the efficacy of all insecticide groups and minimise resistance risks, it was vital to rotate products within and between seasons.
“Every time a broad-spectrum insecticide is used to control pests, such as weevils, caterpillars and aphids, RLEM also receive a dose of this insecticide - despite not necessarily being the primary target,” she said.
“If sprays are required against a pest, for example aphids, consider using alternative controls to OP (Group 1B) or SP (Group 3A) insecticides, such as seed dressings to deter early colonisation of aphids rather than spraying.”
Ms Micic said it was imperative to prepare paddocks for the next season to lower pest numbers and reduce reliance on chemical pest control.
“Weed control over summer, both in paddocks and along fencelines, is a key activity to minimise the risk of a ‘green bridge’ carrying mites as well as other pests into the following crop,” she said.
RLEM is estimated to cost Western Australian canola growers $3 million per annum in lost production. If the pest was not controlled it is estimated the cost could rise to $50m per annum.
For more information about RLEM control options click here.
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