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pestmanagement


Biological weapon sought to fight SWD


Growers urged to not inadvertently ‘feed’ female Drosophila fly. By Judie Steeves


E


fforts are under way to find a parasitoid that could help manage infestations of the


Spotted Wing Drosophila (SWD), or a predator that could help reduce their populations, but in the meantime officials are urging growers to ensure no ripe or over-ripe fruit is composted or left in the field. That provides a food source for the female, explains Sheila Fitzpatrick, a research entomologist with the Pacific Agri-food Research Centre in Agassiz.


And, that female can lay 350 eggs in her short lifetime, if she can find enough ripe fruit in which to lay those eggs.


Eggs hatch in 12 to 72 hours, depending on temperatures, and the female can lay 20 to 30 a day, one to three eggs per fruit.


The larva go through three instars while feeding on the fruit in five to seven days, before emerging as adults, then this species of vinegar fly, similar to a fruit fly, mates and repeats the cycle.


Eggs are bullet-shaped and stuffed into holes in the fruit created by the female’s two rows of teeth on her ovipositor that act like a bread knife on fruit, explained Fitzpatrick, cutting a trench in which to lay the eggs.


The female egg-laying scars the fruit and, once the larva begin feeding, the fruit becomes soft. Infested fruit becomes a breeding site so it’s important all ripe fruit is


14 British Columbia Berry Grower • Fall 2010


removed from the field and destroyed by burying, tightly bagging it, or freezing it. Fitzpatrick said it’s also important that all fruit be picked, not left on the plant, to help reduce feed and host fruit for breeding.


Unfortunately, she said, often there are alternate hosts nearby such as wild blackberries.


JUDIE STEEVES


Contech traps are being used to monitor adult SWD populations in fields, but a formula for yeast, sugar and water also works, said Fitzpatrick.


PARC entomologist Sheila Fitzpatrick. predatory mites as well.


If flies are found, there are a number of chemicals that have been registered this year for use against SWD, although she warns they are also toxic to bees and some to


Dave Gillespie of PARC is working on finding a parasitoid against SWD, but there is a rose beetle which may help in controlling populations too. The bottom line is the SWD is here in B.C. now and it’s not likely it will go away.


For details and up-to-date data on local infestations, go to:


www.agf.gov.bc.ca/cropprot/swd.htm


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