Researchers detail ongoing work to combat fruit fly pest

Spotted-wing drosophila (SWD) "is now widespread geographically" in England, while an extensive monitor trap programme this year failed to prevent the fruit fly laying eggs in fruit, the soft-fruit day heard.

Drosophila: work being carried out to find a suitable predatory mite - image: G Steck
Drosophila: work being carried out to find a suitable predatory mite - image: G Steck

The fight against the pest is proceeding on several fronts, said Dr Michelle Fountain of East Malling Research (EMR). Having tested the efficacy of insecticides on strawberries last year, EMR researchers have this year looked at controls on raspberries, with Chlorpyrifos giving a kill rate of close to 100 per cent in trials.

Pairings of trap design and attractant solution "is something we are still working on", she said. In trials so far: "The best trap for SWD also had a lot of by-catch."

Trap baits being developed in sachet form "wouldn't need to be changed so often", she added. "The combination of attractants and pesticides has potential."

Meanwhile, for growers: "Crop hygiene is so important. You can't just leave fruit lying around where it will be a source of the next generation of flies. In sealed bins at 18 degsC or above they will not survive beyond two days. But it can't then just be poured on the ground. It has to be incorporated into the soil or mixed with 90 per cent dry matter."

Fountain added: "Get traps in woodlands and hedgerows, and continue to monitor from February through to November when your tunnels come down."

Meanwhile, fruit can be tested for larvae by crushing with a solution of salt or sugar. This ensures spraying is targeted because some controls have only one or two permitted applications.

"Spray cherries only as they come into maturity, which will be at a different time for different varieties, otherwise you will run out of sprays." EMR's own cherry crop had to be ploughed in due to infestation, she added.

EMR entomologist Dr David Buss is working to identify a suitable predatory mite against SWD. The challenge is to breed one that is resistant to conventional pesticides, he said.


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