Apple growers on fire blight watch

Dan Wheat/Capital Press Esteban Gutierrez, a Washington State University scientific assistant, applies a fermented bacteria to Red Delicious apple blossoms at the WSU Tree Fruit Research and Extension Center in Wenatchee on April 9. The material is being tested as a fire blight control.

WENATCHEE, Wash. — Fire blight probably won’t be a big problem in Washington apple and pear trees this season but it could be an issue in New York, a tree fruit specialist says.

Apple trees in New York are blooming now and “they’ve had some very serious fire blight infectious weather,” said Tim Smith, Washington State University Extension tree fruit specialist emeritus.

“They are very cognizant of it and are working to prevent it,” he said.

The bacteria kills apple and pear trees. It overwinters in trees and reactivates in oozing cankers around blossom time. It attracts flies and other insects that spread it to blossoms. Within a week or two, withering is apparent.

It was once only a concern in pears but has damaged apple trees in Washington since 1993, with 1997 and 2012 being the worse years, Smith wrote in a 2012 paper. Thousands of acres of older Gala and Fuji apples were blighted in 2012 when rain followed a late April warming, he wrote.

Blight is exacerbated by extreme heat followed by rain or heavy dew.

That’s happening now in New York and happened last year in Pennsylvania, he said.

Washington isn’t totally out of the woods with susceptibility in secondary bloom in the next two weeks but the larger worry of primary bloom is past, he said.

“There is a lot of secondary bloom in pears and not as much in apples this year,” he said.

Secondary bloom is a fresh blooming that occurs up to four weeks after the first bloom. Secondary can be more vulnerable because there’s more warm weather, he said. It damages trees in lower levels and propagates the disease for the following year.

A bad hit on primary bloom is more serious because there’s a lot more blossoms in primary bloom, Smith said.

“We had some periods that neared danger in some areas. It’s temperatures in the 80s and higher and we’ve skirted that,” he said.

Central Washington is having a relatively dry spring of gradual warming, which helps, he said.

In recent years, a week of 90-degree weather in early May has been common and “gets spooky,” Smith said.

Fire blight was worse in areas around the Tri-Cities in 2012 and in the Okanogan in 2013, Smith said. Antibiotics, copper fungicides, minerals and biological controls are used to combat it. Infected portions of trees should be cut out when spotted instead of waiting until winter, he said.

Smith is testing fermented products of other bacteria as an alternative to antibiotics.

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