A new soft fruit pest may spell the end for organic cherry growers, an entomologist from Washington State told a horticultural symposium for orchardists held in Kelowna last week.
Betsy Beers, of Washington State University, said growers were unprepared for last year’s arrival of the tiny vinegar fly, the Spotted Wing Drosophila, because they believed climatic conditions such as the dry, hot summers and cold winters here would prevent it from becoming a problem here.
The SWD seemed to spend seven or eight decades happily in Asia, then three more in Hawaii, but three years after that it was everywhere, she said.
“I’ve never seen anything like it in my career,” added Beers.
The fly’s first appearance was in late 2009 in Washington and B.C., and it also appeared in 2009 and 2010 in Italy, Russia, Spain and France, as well as on the eastern coast of the U.S., and even in Ontario late last year.
Beers said many in the B.C. industry organized rapidly last year to deal with the new pest but admitted in Washington their counterparts were a bit slower getting getting started because they really didn’t believe it would be an issue.
“This pest doesn’t respect borders, so we’re all in this together,” said Beers
And, she added, the fly seems able to establish itself everywhere and can be devastating.
“I don’t think anyone is immune from this.”
In addition to infesting orchards, Beers said the fly will attack native plants such as Oregon grape, black currant, blue elderberry, cherry laurel, mulberry, serviceberry and chokecherry.
“So, the battle will be everywhere, not just in orchards.”
Local cherry growers had only in recent years been able to vastly reduce the number of chemical sprays against the cherry fruit fly with use of a new bait called GF-120. So they are disappointed to now have this new pest in their orchards, threatening crops and requiring the use of those sprays again.
The SWD seems to be most attracted to cherries, Beers told the growers.
It does not seem too enthusiastic about wine and juice grapes, which may contain too much acid to be attractive.
But she said the fly does attack table grapes.
Unfortunately, this pest not only has a short life cycle but females can lay 219 to 563 eggs and in the summer can produce a new generation every 10 days.
By last October and November, she said traps were catching thousands of SWD, indicating a rapidly-increasing population of the pest.
She expects that pattern to continue this year, with the largest populations building up late in the year.
Contrary to local authorities, she minimized the importance of clean-up in the orchard in the fall as a factor in overwintering populations.
Growers also learned about issues such as combatting rain-splitting problems, mildew spore monitoring, cherry nutrition, early cherry varieties, and held the annual general meeting of the Okanagan-Kootenay Cherry Growers’ Association at Friday’s sessions.