US (OR): Fireblight on rampage

Pear orchards have been hit hard by fire blight across the Rogue Valley this year, keeping growers and their crews searching high and low, cutting out infected limbs — or in extreme cases whole trees.

"Fire blight is absolutely horrible," grower Gary Hubler said. "The past several years have been terrible. It's costing a lot more money to put on blight spray this year, and now it's too late in the season. If we find any blight, we have to cut it out and remove it."

By long-standing Jackson County ordinance, infected pear branches or trees have to be burned, disposed of or taken to a landfill.

Although the previous two growing seasons were challenging for growers, David Sugar, a pathologist at the Oregon State University Southern Oregon Experiment Station, said this year's double-barreled fire blight assault can be blamed on the sun.

"When the pears were in full bloom in mid-April, we had highs in the mid-80s," Sugar said. "It was a real warm spike and very conducive to fire blight bacteria. All of the growers I've spoken to have varying amounts of blight. They want to destroy it as quickly as possible — that's why you've see plumes of smoke around the valley. They have a special exemption to the burning law, because of how critical it is."

The Experiment Station staff charts temperatures during bloom to determine the extent of blight risk in the coming weeks.

"Our model gives a score for each degree warmer it gets," Sugar said. "The warmer the temperature, the higher the risk, and this year it was off the chart. Usually, when it's 60 degrees or below, there is no risk at all. In the 70s, we watch the model closely. But when it gets into the 80s during bloom, we don't need a model — we've got infection."

Source: mailtribune.com