A way of disposing of softand stone-fruit waste without attracting the invasive spotted-wing drosophila (SWD) has been developed by an industry-led research team.
Dr Michelle Fountain, an entomologist at East Malling Research, revealed the process at the Kent research station's soft-fruit technical day last month.
She explained that the pest, small numbers of which were found in English soft-fruit crops for the first time this season, is also attracted to and infests fruit waste.
Developing ways to safely dispose of unwanted fruit has been one of the main aims of the industry's response to the SWD threat. Fountain said growers' fruit waste was collected from the fields and put in containers kept in sealed pallet bins to ensure that the conditions inside were anaerobic.
"Analysis showed that no SWD adults were found when the fruit had been inside the pallet bin for a day," she said. "No live eggs, larvae - which withstand hours without oxygen - or pupae were detected after 13 days."
Stored fruit waste separates into two layers, with 90 per cent turning into a clear liquid and the rest forming a surface crust of skins and stalks, she explained. Liquid "rapidly soaked into the soil", but disposal of the crust is more difficult.
Analysis 11 days after the waste had been disposed onto land showed that crust on the soil surface was still attracting SWD. However, there was no SWD present where the waste had been incorporated 10cm into the soil. Similar results were recorded for both soft and stone fruit, Fountain added.
Researchers will continue to develop the method, which will be used to help form a nationwide SWD-control strategy.
Fruit fly: Higher populations in woodlands
Populations of spotted-wing drosophila were higher in woodlands surrounding fruit farms than on the farms themselves, a nationwide, industry-led monitoring programme found this season.
The pest, found in woodlands in most weeks, first emerged in areas with the highest number of elderberry and blackberry bushes. Researchers also tested the efficacy of seven active ingredients for their ability to protect strawberry crops from the pest. Spinosad (Tracer) and chlorpyrifos did well in the trial, giving up to 13 days' protection.
Pyrethroids "worked well for the first couple of days but not after that", said entomologist Michelle Fountain. She warned that there is "an urgent need" for more insecticide approvals, particularly for cherry and blueberry crops.