Pears at risk

Unusually humid conditions for this area have contributed to a fire blight outbreak that may reduce yields, says OSU plant pathologist
Orchardist Gary Hubler studies a pear tree branch with blackened leaves and discolored bark, which are signs of fire blight infection.Mail Tribune / Bob Pennell

Fire blight, the ever-present enemy of pear growers, is posing an exceedingly ugly threat this summer.

A combination of meteorological and orchard elements have combined to endanger Comice and Bartlett crops.

"At least for Comice trees, it's as bad as any year in memory," said David Sugar, a plant pathologist at the Oregon State University Southern Oregon Experiment Station. "It's particularly severe in Comice and Bartlett trees, but not as bad in Bosc."

Warm temperatures at the end of the bloom period aided bacteria growth, setting the stage for an all-out assault in late May and early June. An extended bloom period made Starkrimson and Bartlett varieties more vulnerable than usual.

"The very humid, warm period we had at the beginning of May supported very lush, tender growth in the trees," Sugar said. "Then we had some very windy days that banged around those new shoots, causing little injuries that allowed the bacteria to enter."

The present warm, moist conditions have added to pear grower woes.

"Bear in mind most of the country doesn't grow pears because fire blight is impossible to manage under humid summer conditions," Sugar said. "We hope this (marine air) goes away soon."

Once fire blight takes hold, growers can lose a branch, half a tree or a whole tree. Branches look blackened, and the fruit becomes coal-black. Bacteria causing the blight oozes out of the infection and runs down a branch, staining the wood as it goes.

Gary Hubler, who has trees outside Phoenix and in northeast Medford, said he has difficulty especially with Bartletts.

"I've had to do total replacement sometimes," Hubler said. "By the time you take a limb or two on some of them, there isn't much of a tree left. It travels through the air, to the trunk, center, top, tips and limbs. You don't know it's infected until it's too late. A lot of times you can't salvage it."

Hubler worries people with a pear tree or two in the backyard may unwittingly contribute to fire blight's spread by not taking action.

A few weeks ago, orchardists predicted this year's crop would be 3 or 4 percent bigger than last year's. Fire blight could put a dent in those predictions.

"Quantifying (potential) damage is difficult to do," Sugar said. "There are pockets of it here and there in an orchard and occasionally every tree in an orchard is affected and needs to be cut. Most commonly there are severe pockets, less severe pockets and completely healthy areas. In those severe pockets, some trees need to be completely cut down or have major limbs completely removed to keep the entire tree from being killed."

Luis Balero, orchard superintendent at Associated Fruit, said the blight has kept his crew busy, but there's only so much that can be done. Associated has a significant amount of Bosc blocks, which have been less susceptible.

"I don't think it's real critical yet, because we don't have that much Comice," Balero said. "There's nothing you can do right now, just cut it and burn it."

Reach reporter Greg Stiles at 541-776-4463 or business@mailtribune.com. Follow him on Twitter @GregMTBusiness, and read his blog at www.mailtribune.com/Economic Edge.



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