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Wet weather fuels disease pressure

Published on June 26, 2010 3:01AM

Last changed on July 24, 2010 6:09AM

Mitch Lies/Capital Press
Oregon State University plant pathologist Jay Pscheidt says disease pressure has been high in tree fruits this year.

Mitch Lies/Capital Press Oregon State University plant pathologist Jay Pscheidt says disease pressure has been high in tree fruits this year.

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Explosion of rare diseases causing damage across state's orchards

Capital Press

CORVALLIS, Ore. -- Oregon State University plant pathologist Jay Pscheidt is seeing plant diseases this spring that he's never seen in his 22 years at the university.

"They've been reported before," Pscheidt said of the diseases. "It's not like they are brand new. It's just that we haven't seen them in many years."

In a spring that broke rainfall records, common diseases such as brown rots, scabs, anthracnose, blossom blights and leaf spots are flourishing on a variety of fruit crops.

Rare diseases, such as apple rusts, also are showing up.

"It's not necessarily the volume of rain as it is the length of the wet period (causing the eruptions)," Pscheidt said. "The longer the wet period, the more they like it."

"Rusts are going crazy," Pscheidt said. "The Pacific Coast pear rust has been particularly nasty."

In most cases, Pscheidt said, growers are able to hold diseases in check by intensifying treatment programs.

But, Pscheidt said: "If there's a hole in somebody's (fungicide-treatment) program, it will probably show up."

Some growers are doing everything right, Pscheidt said, but because of difficulty getting in fields or because of resistance, they are suffering losses.

Ray Fujii, of Fujii Farms in Troutdale, Ore., said wet conditions have forced the farm to forego some treatments. As a result, the farm has seen an increase in rots and molds.

"We've probably down 10 to 15 percent," Fujii said.

Also, he said, the rain has reduced traffic at his fruit stand.

"The sunshine brings out buyers," he said. "This rain is hurting sales."

The one positive, Fujii said, is cool conditions are extending the strawberry season. The normal three-week season could stretch to five weeks, he said.

"Overall," he said, "it's not disastrous, but it could be a lot better."

Roy Malensky, of Oregon Berry Packing, said his strawberries are doing great.

"I'm surprised," he said. "I thought it was going to be a problem what with all the rain, but the growers did a great job of putting fungicides on and the fruit is in surprisingly good shape."

Blueberries, on the other hand, are suffering, Malensky said.

"We're seeing a lot of problem with botrytis, particularly in the duke variety," he said.

In cherries, brown rot blossom blight has erupted, Pscheidt said. Where he didn't spray, Pscheidt said the blight is causing 50 to 80 percent losses in his cherry plots.

"I have not seen it this bad in the 22 years I've been here," Pscheidt said.

Leaf curls and other foliar diseases that can affect next year's crops also have erupted.

"The foliar diseases, because of the wet weather, have gone bonkers," Pscheidt said.

And then there are the rare diseases, such as apple rusts.

"It's the first time I've seen those rustations on apples," Pscheidt said.

The Pacific Coast pear rust, which causes malformation in pears, is common in the Willamette Valley, but typically isn't economically significant.

This year it is, Pscheidt said.


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