Goemeone Obonye with WA grain grower and stockfeed processor Ray Smith discussing grain storage issues at Ray’s farm.
By Jeff Russell, Grains Biosecurity Officer for WA
Phosphine resistance in grains pests is an increasing problem world-wide, and research carried out in Western Australia reveals that it’s likely to get worse as the climate warms, at least for some species.
Goemeone Obonye, a research student from Botswana, investigated rates of phosphine resistance in stored grain pests to test the idea that a warmer climate will speed up the development of resistance to this crucial and widely used pesticide.
Goemeone undertook the research to investigate factors associated with higher rates of resistance to phosphine as part of a Masters of Biosecurity degree at Murdoch University.
He investigated two common stored grain insects: the lesser grain borer (Rhyzopertha dominica) and red flour beetle (Tribolium castaneum).
To find out if warmer climates accelerate resistance, Gomeone analysed rates of insect resistance in grain producing areas above and below the grain export port of Kwinana in WA. He compared data from the Australian Grain Insect Resistance Database for Western Australia for the cooler and warmer areas.
If resistance rates in more northerly latitudes were higher than those in the cooler south, it suggests increasing temperature plays a role in resistance.
The results showed that for the lesser grain borer, warmer latitudes were associated with higher rates of phosphine resistance. Red flour beetle didn’t show the trend, suggesting that the effects of a warming climate on the development of phosphine resistance will be species specific.
According to Goemone, the study indicates that climate change will intensify phosphine resistance in at least some species of stored grain pests. “Warmer conditions are thought to increase phosphine resistance by speeding up breeding of insect generations and allowing further spread of pests, and this research confirms the trend for some pests,” he said.
Although the research was done on data from Western Australia, Goemone said that the findings are applicable to grain growing regions around the world, including in his home country of Botswana.
He urges growers everywhere to take care to only fumigate in sealed silos to maintain the effectiveness of this key protection against stored grain pests.