Cold winter would help curb SWD


This year has seen continued spread of the invasive fruit fly in our region.


By Judie Steeves A


mild winter and early spring provided ideal conditions for breeding by the invasive new pest of soft-skinned fruit, Spotted Wing Drosophila, according to agriculture ministry entomologist Susanna Acheampong.


And, if this coming winter proves to be mild, next year’s growing season could see even more prevalence of the devastating insect. Cherries are a favoured food for the Asian vinegar fly’s larva, which hatch inside ripening fruit after the adult female fly lays its eggs inside the fruit. It was first discovered in the Pacific Northwest in 2008. By the next year populations had grown so rapidly whole crops had to be abandoned in the U.S. In 2010, SWD was discovered infesting crops in both the Fraser Valley and the Okanagan.


“Cold weather is needed to kill it off over winter,” comments Acheampong.


The previous season numbers were not too high, but following last year’s mild winter the numbers were really high this summer, she says. SWD also causes damage to apricots, but because peaches are usually not ripened on the tree, that crop is not as vulnerable to attack as cherries, and apples are not affected. Even grapes, both wine grapes and table grapes, don’t seem to be on the little fly’s menu, she says, although it depends to some extent on the variety and if they are thin-skinned varieties.


On the whole, though, “They don’t seem to have a preference for grapes. They prefer cherries,” she adds.


She says she has had a lot of calls British Columbia FRUIT GROWER • Fall 2015 19


from homeowners with fruit trees complaining about SWD in their fruit. She advises them if they can’t maintain their trees to keep them free of pests they should remove the trees.


Professional pesticide applicators


are required to control such pests in Kelowna, which has a bylaw banning the use of pesticides for cosmetic purposes except by professionals. Research is underway to find an alternative to pesticides to control SWD, but no answers have been found so far.


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