If you grow berries or other soft fruit in the Pacific Northwest, be prepared for a bad infestation of the spotted wing drosophila fly this season, say experts.

"All indications estimate this season will be similar or worse than 2012, which was the worst on record," Oregon State University Extension entomologist Vaughn Walton said in a news release.

He blamed warm winter and spring temperatures, which tend to enhance pest populations.

Walton said he expects fly populations to peak in July and August, when fruit is most susceptible.

Unless most fruit flies, which prefer rotting fruit on which to lay their eggs, the spotted wing drosphila seeks fruit just nearing maturity on which to oviposit.

Among its hosts are strawberries, blueberries, cherries, blackberries, raspberries, peaches and plums.

The pest has not affected winegrapes so far, Walton said.

Several pesticides are registered to control the pest.

The arrival of the pest has prompted many growers to increase the number of insecticide treatments they apply annually.

Before the fly, farmers in the Willamette Valley and Oregon's Mid-Columbia Basin typically applied treatments twice annually to manage other pests.

Last year, they applied an average of five to nine treatments to control spotted wing drosophila at a cost of about $169 per acre, according to the release.