By MITCH LIES
Oregon researchers are advising strawberry and cherry growers to keep a sharp eye out for the spotted wing drosophila as a mild winter and warm spring could escalate its threat to early-maturing fruit.
Scientists believe cold and rainy spring weather the last two growing seasons delayed plant growth and fly development, and helped some growers escape damage.
"This year, earlier crops such as strawberries and potentially cherries will be more susceptible than they were the last two years," said Vaughn Walton, Oregon State University Extension entomologist who is based in Corvallis.
"From what we've learned from the last two years, we are more at risk now because I think we have higher levels that have survived the winter," said Peter Shearer, a Hood River County extension entomologist.
Walton and Shearer advise growers to watch regional trap counts and do their own trapping to monitor pest populations.
"Trap in fields and surrounding vegetation," Walton said.
Also monitor fruit development, Walton said.
The riper the fruit, the higher its susceptibility, Walton said.
Shearer estimates early cherries in the MId-Columbia region will be nearing straw color by June 1, at which point they will be susceptible to fly damage.
The spotted wing drosophila scars fruit by depositing eggs inside it with a saw-like ovipositor. Soft skin fruit, such as strawberries, cherries, blackberries and raspberries, is particularly susceptible.
The pest is native to Asia.
Oregon State University Extension researchers this year are compiling a newsletter that provides updates on trap counts and research into the pest.
The first four newsletters are available in hard copy, which the extension service will mail to interested growers. All nine newsletters will be posted on OSU's spotted wing drosophila website.
The service issued its first update, which focused on strawberries, May 4. Its second newsletter, which will focus on blackberries, will be out the week of May 21, said Wei Yang, an OSU berry crops extension agent based in Aurora.
The service also will release its annual report on the spotted wing drosophila to the general public the week of May 21, Walton said.