Researchers seeking biological weapon By Judie Steeves E


fforts are underway to find a parasitoid that could help manage infestations of the Spotted Wing Drosophila, 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.


Ripcord have received emergency registration against SWD until the end of October, but should only be applied when flies are present and fruit is at the susceptible stage. All are toxic to bees. Growers can contact their field service representatives or crop consultant regarding control, once adult flies are detected. As well, a post-harvest cleanup spray is strongly recommended and also will help control populations of cherry fruit fly for next season. Since SWD will infest berries, cherries, apricots, peaches, nectarines, plums and grapes, as well as wild fruits such as Oregon grape, saskatoon, elderberry and pin cherries, it’s important to control adults in all the areas any of those are grown, commercially or wild.


“It’s here and it’s widespread and we will have to change our management practices,” commented Leaming. Lots of data is being collected throughout the valley for study over the winter, so that a management plan can be put together for next year. Agriculture ministry entomologist Susanna Acheampong agrees that sanitation is critical. She says there will be meetings for growers in the fall and there may need to be more products certified to work on this pest. There is research underway into a product similar to GF-120, but for SWD, but no one knows how long it will


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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 removed from the orchard or vineyard and destroyed by burying, tightly bagging it, or freezing it. Fitzpatrick said it's also important that all fruit be picked, to help reduce feed and host fruit for breeding. Unfortunately, she said, often there are alternate hosts nearby such as wild cherries, saskatoons or Oregon grape. Contech traps or vinegar traps are being used to monitor adult SWD populations, but a formula for yeast, sugar and water also works, said Fitzpatrick.


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 predatory mites as well. 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 is not likely to go away.


For details about management of SWD, go to: www.agf.gov.bc.ca/cropprot/swd.htm


be before it’s available.


Kelowna cherry grower Christine Dendy notes the most frustrating thing is that all growers’ efforts to reduce the use of toxic sprays has been to no use, now that they have to be applied to combat SWD.


She is concerned that small growers and grape growers realize this new pest is here in B.C., that it overwinters here and that it must be controlled by everyone cooperating.


In her operation, she says they instituted super-sanitation in the packinghouse, which helped keep them clean of SWD. They sprayed cull piles and buried fruit; clean-picked trees so no fruit was left in the orchard after


harvest. They controlled them in wild hosts such as saskatoons and Oregon grape by spraying the margins of the property and they used a food-safe pyrethroid around the packinghouse and fruitstand at night. Employees were included, to ensure their leftovers from snacks and lunches were properly disposed of.


The one bright spot in the whole scenario is that there was only one capture of an adult SWD by mid-August in the Creston area, for some reason, notes Acheampong, contrary to the story everywhere else in the Okanagan and Similkameen Valleys.


CERTIFIED ORGANIC AMBROSIA APPLE ORCHARD


on 5.47 acres of BENCHLAND


in the Similkameen Valley (45 minutes from Penticton)


WA Dawson, Orchardist Cawston, BC


wadawson@nethop.net 250-499-2873


British Columbia FRUIT GROWER • Fall 2010


FOR SALE


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