WENATCHEE, Wash. — A new test kit is available for cherry growers to determine if their trees have Little Cherry Disease.
The kit is a relatively quick and inexpensive tool for growers compared with more expensive molecular diagnosis only done in laboratories, said Elizabeth Beers, entomologist at the Washington State University Tree Fruit Research and Extension Center in Wenatchee.
Little Cherry Disease is a virus that results in small, bitter-tasting cherries that are unmarketable. The disease almost wiped out British Columbia cherries in 1933 and has been detected in Washington since the 1930s. It is believed to exist at low levels in Washington but has been noticed more in recent years, Beers said.
Agdia Inc. of Elkhart, Ind., a leading provider of test kits for plant pathogens, has just begun selling the kits. It costs about $300 for a heating block and other setup supplies and then $240 for a package of eight kits, Beers said.
Growers take leaf samples from suspect trees and, using kits, grind them, add chemicals and follow a process to get results.
About 200 acres of trees were removed in 2013 on Wenatchee’s Stemilt Hill and Wenatchee Heights, prime cherry growing areas, in efforts to stop spread of the disease, Tim Smith, WSU Extension specialist has said. About 200 to 400 acres should be removed in the Wenatchee area, he said in January. It is the only way known to stop the disease, which is believed to be spread by mealy bugs and tree roots grafting into each other.
Beers heads a new, three-year research project, funded by Washington, Oregon and California, to better understand the disease and develop a strategy to manage it.
“We’re trying to determine the prevalent form of spread. If it’s root grafting there’s not a lot you can do except remove the tree. If it’s the vector (insect transmission) then we need to control the vector and remove infected trees,” Beers said.
The apple mealy bug historically has been considered a vector but Ken Eastwell, WSU plant pathologist in Prosser, discovered the grape mealy bug also carries the disease.
The disease has been verified in commercial cherry orchards in Chelan, Douglas, Okanogan and Grant counties — all in north Central Washington. It appears most prominent in Wenatchee perhaps because mealy bugs prefer apples and pears and there are lots of cherries in close proximity to them, Eastwell has said.
Kyle Mathison, vice president of Stemilt Growers Inc. and president of Kyle Mathison Orchards, has said he removed 100 acres on Stemilt Hill and Wenatchee Heights in 2013 to fight the disease. He said it can take years to get back into production.
He could not be reached, but Efrain Reyes, general manager of his orchards, said he hasn’t seen suspect trees at lower elevations so far this season. He said he will be watching trees nearer the Stemilt warehouse on top the hill. That’s where the problem has been and is evident when cherries start to ripen about two to three weeks before harvest, he said.
Information about the kits and disease is available online at www.tfrec.wsu.edu.