New Pest Poses Threat To Cherries
Judie Steeves -
Kelowna Capital News Published:
February 09, 2010
A new and devastating pest of soft fruits like cherries and grapes has made its way to North America and was discovered in an East Kelowna cherry orchard last fall. Spotted wing drosophila, a vinegar fly, can destroy an entire crop of cherries in a season, despite its tiny size. And cherry growers who are members of the Okanagan Kootenay Cherry Growers’ Association voted at this week’s annual general meeting to fund a monitoring program that will include trapping, identification and fruit inspection to map the progress of this new pest in the Okanagan, Similkameen and Creston Valleys, where cherries are grown. Entomologists from the agriculture ministry and the Pacific Agri-food Research Centre in Summerland are working with counterparts in California, Oregon and Washington, where the pest was also discovered last year, to put together an emergency management strategy for the fly. Susanna Acheampong, Kelowna entomologist with the ministry, said it’s expected overwintering flies may turn up by May—if there are any—so monitoring must begin before then.Emergency registration of a pesticide to help deal with an infestation may be needed, but it’s not known yet what might work best against it.
A December pest alert from the ministry warned all growers of stone fruits like cherries, peaches and apricots, as well as dogwood, mulberry and berries, that it has been confirmed in the Fraser Valley and Kelowna. On farms where it was found in the Williamette Valley in Oregon in peaches, some growers lost up to 80 per cent of their crop, while in Northern California, about a third of the cherry crop was lost to it last year. It’s native to Asia, but can be transported in ripe fruit like berries, cherries or grapes, where the adult lays its eggs under the skin of the fruit, so the larva have an ample food supply once they hatch.The females can lay 16 eggs a day and average 384 eggs per female. The eggs hatch in two to 72 hours and the larvae mature in three to 15 days. Unlike other “fruit flies,” the spotted wing drosophila infests fruit just before harvest, rather than over-ripe or rotting fruit, which could have a devastating economic affect in the valley. Adults can be blown by the wind to infest new fruit on neighbouring farms or they can be transported by infested fruit to new regions.
Although it was discovered locally last fall, PARC entomologist Howard Thistlewood said there’s no way of knowing whether they will arrive early here, as overwintering adults or if they will come in on supermarket fruit. Okanagan Tree Fruit Co-operative field services manager Hank Markgraf said there’s the potential of five or six generations a season here.“So they can get wildly out of control in one season,” he said. Kelowna grower David H. Geen said it’s important that the ministry sit down with grower groups (including grape growers) to come up with a real plan to tackle the issue.“Look at the effort the country had to put into mad cow disease,” he commented.
