Useful insects bring balance
A NATIONAL project funded by the Grains Research and Development Corporation (GRDC) has concluded that grain growers can generally get away with one less insecticide spray during the growing season - without sacrificing yields.
The project - "Developing and promoting Integrated Pest Management (IPM) in Australian Grains" - looked at understanding insect pests and first assessing insect damage on emerging plants before deciding to spray, rather than relying on pre-emergent "insurance" sprays and applying "softer" insecticide sprays only when needed.
Entomologist Laura Fagan, who led the Western Australian component of the project, said on-farm field trials showed that monitoring - a key IPM component - could reduce the need for conventional chemical sprays without affecting yield.
"Most of the farmers involved in the project realised they can get away with one less spray in the season and still get the same outcome," she said.
"For canola, it seems that in years following heavy drought or in years with above-average rainfall and low pest pressure, the best course of action for a farmer is to not apply pesticides.
"For wheat, applying less chemical appears to be the best practice, as similar yields can be achieved without the extra cost of applying chemicals."
Darryl Hardie, national project leader and Department of Agriculture and Food (DAFWA) senior entomologist, said the project was still working to produce a conclusive answer as to whether IPM was the best insect pest management approach in all Australian farming systems.
"However, the project showed that, following a rotation of pasture, canola, then wheat, the IPM approach was equally or more effective than the 'farmer approach' with respect to grain yield," he said.
"Farmer approaches" tested in the project were based on current or conventional pest management practices within each of the local areas or regions.
Dr Hardie said that, overall, pest populations were generally higher than beneficial insect populations in a paddock, regardless of the management approach.
"But importantly, the beneficial insect-to-pest ratio in the IPM plots was always higher than the ratio in the 'farmer approach' plots.
"This means the pest population was lower with an IPM approach because the beneficial insects were more abundant in these plots, compared with the 'farmer approach' plots."
