Spotted wing drosophila is a diminutive but prolific fruit fly pest with a penchant for fresh and ripening fruit.
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It lays its egg within soft fruit, causing it to decompose and resulting in an estimated $623 million loss in the B.C. soft and thin-skinned fruit export market. Most fruit fly research is in British Columbia, but the threat exists in Ontario too.
Why it matters: Parasitic wasps could offer tender fruit growers a biological option for controlling fruit flies, reducing the need for insecticides.
In 2011 OMAFRA began monitoring drosophila traps in tomato sites. The highest pressures were found in Essex, Kent and Norfolk but the flies weren’t yet infesting the fruit.
Growers use insecticide to minimize the impact, but new research suggests the parasitoid samba and ronin wasps are potential biological controls.
In 2018, Agriculture and Agri-Food Canada research scientist Paul Abram and the Agassiz Research and Development Centre in British Columbia planned to introduce the wasps to B.C., only to discover they had already arrived in the Fraser Valley. By 2020, they were common along the southern coast.
“The fact that it has come to B.C. on its own gives us the opportunity to see how it interacts in the reality of Canadian nature,” Abram said in an AAFC statement.
“Is it only attacking the pest, or does it have a broader impact?”
In 2020, both types of wasp killed 13 to 53 per cent of drosophila larvae in natural habitats on 13 species of crop and non-crop fruiting plants, with no perceived negative impact on the wider ecosystem.
Abram hopes to develop a formal consultation and documentation process for introduction of biological control agents within Canada.
His research and collaboration with American colleagues has led to published recommendations for sampling and identifying the wasps while developing instructions to identify emerging parasitoids that attack the fruit fly pest.
In 2022 Michigan State University launched a research program that saw the mass-rearing and release of samba wasps on nine farms from South Haven to Travers City, Michigan, with plans to add another 20 sites in 2023.
If the parasitic wasp shows resilience in the northern state, it could provide a strong base for initiating a similar program in Ontario.