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Life cycle of the Spotted Wing Drosophila
The spotted wing drosophila destroys fruit because the female lays her eggs in the fruit itself, which cannot be sold fresh if it has fruit fly larvae in it. Most of that fruit is used for juice, fetching a much lower price for the grower.
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Washington State University
Vinegar Fly hard at work, destroying fruit crops
The Spotted Wing Drosophila doesn't just feed on fruit; the female also lays eggs in the fruit itself. Then the eggs hatch into larvae, the fruit softens and can no longer be sold as fresh fruit.
A tiny but massively destructive bug will be the focus this year when hundreds of berry growers meet at the Pacific Agriculture Show in January.
The Spotted Wing Drosophila, or vinegar fruit fly, was discovered in BC in 2009. Since then this pint-sized pest has spread throughout the Lower Mainland.
“This has been the worst year ever in the Fraser Valley for this pest,” says conference organizer Mark Sweeney. “It has been a tough year with big challenges.”
Sweeney is co-organizer of the Horiculture Growers’ Short Course, which is the conference portion of the Pacific Ag Show. He is also an Industry Specialist in the Fruits and Nuts division at the BC Ministry of Agriculture.
Sweeney says it’s difficult to quantify the losses, but reports from growers show massive losses over the past growing season.
“It’s hard to get a handle on the dollar value of the losses, because it’s not like the fruit is simply thrown out,” he says. “What happens is the fruit gets downgraded, from fresh to frozen, and from frozen down to juice, depending on the damage. In dollar terms you might get 80 cents to a dollar a pound for fresh, and only 20 cents for juice, so you can see it can have a dramatic impact.
“This year we had more downgrading of berries than ever before.”
A panel of growers and researchers will be examining ways to do battle with the fruit fly invasion.
A series of seminars at the Ag Show will examine management methods to reduce the damage, but at this point, Sweeney says there is no magic bullet that can seriously reduce the spread of the Spotted Wing Drosophila.
“There is a lot of research going on around the world, and the troubling thing is at this point there is no breakthrough,” Sweeney says. “In the long-term the question is whether there is a method of ‘bio-control’ for this fly, which might be a parasite or might be a natural predator, but at this point there is nothing like that out there.”
The Spotted Wing Drosophila originally came from Asia, and spread throughout the world mainly due to global fruit exports. It was first spotted in BC in 2009.
Almost all berries and fruits are vulnerable to the vinegar fly. That includes rasperries, strawberries, cherries and blackberries, but in BC the biggest worry is the blueberry crop. Last year, BC’s growers exported $168 million in blueberries, and sold much more locally.
The vinegar fly lays its eggs in the berry, which hatch inside as larvae. While not harmful to humans, this causes the fruit to soften. Sweeney says fruit cannot be sold fresh if it has larvae, and often these fruits are turned into juice.
Right now, without a bio-control method in sight, growers are being advised to spray their ripening blueberries and strawberries once a week during harvest. However, Sweeney says that brings its own challenges.
“On the management side there is more spraying required, but this means tractors are going through the fields at harvest time,” he says. “As you can imagine, this not only means more work and more cost, but it can also cause some damage.”
The schedule and speakers for the conference at the Pacific Agriculture Show has not yet been finalized, but Sweeney confirms it will be the major focus this year on the fruit and berry part of the program.
The 2014 Pacific Agriculture Show runs this year from January 30 to Feb. 1.
