Posted: Thursday, January 31, 2013 12:00 PM
Courtesy of Tim Smith, WSU
Little cherry disease cherries, left, are half the size of normal cherries, right. This sample is from the Wenatchee, Wash., area, summer 2011.
Virus once wiped out British Columbia cherry orchards
By DAN WHEAT
WENATCHEE, Wash. -- It's by no means epidemic, but the incidence of little cherry disease has increased the last three years in the Wenatchee vicinity, a Washington State University research scientist says.
Growers need to watch for it and remove infected trees to keep it under control, Tim Smith, WSU Extension tree fruit specialist, told growers at the North Central Washington Stone Fruit Day.
Cool, wet, spring weather in 2010 and 2011 and mixed spring weather in 2012 contributed to the increase, Smith said.
Three or four, 2- to 5-acre orchards were lost to the disease last year, which is negligible commercially. If not addressed the virus "would take out the whole industry," Smith said.
In 1933, the virus all but wiped out the British Columbia cherry industry, he said. Some 60,000 trees, 90 percent of the total, had to be removed. British Columbia experienced another serious episode in the 1970s.
Fruit can be flat on one side, late to ripen and small, Smith said. It usually is still pink when good cherries are to a full ripe red. But the telltale sign is a bitter, acidic taste. Cherries with the virus have little sugar, Smith said.
There's no danger of it being packed for sales because it's too small and bitter to pass packing shed inspections, he said.
In 2010, Smith confirmed 10 out of 10 suspected orchards as having the disease. In 2011, he confirmed 8 out of 8, but in 2012 only 3 of 6 had it.
"I think people got spooked from the prior two years and thought they had it when they didn't," he said.
Irregular ripening with a checkerboard of green, straw (yellowish-pink) and red fruit in the same cluster is likely Western X disease, not little cherry, he said.
"It's not a good one to have either and you'll probably end up pulling the tree," he said.
Most often little cherry disease is not just a limb or two on a tree here or there but larger portions if not entire trees with two to five or six trees in an area having it, he said.
It is spread by mealy bugs and roots of different trees grafting into each other, he said.
There is no cure so the only remedy is tree removal and then probably waiting a year before replanting since replanting too soon can result in the new trees getting it, he said.