MEDFORD - Normally, there are a few hundred yeast cells on a pear that can help naturally heal injuries and protect the fruit from rot - but a million yeast cells would do the job a lot better.

So goes the thinking of Oregon State University scientists who are working on natural, biological controls to thwart the rot that takes a $3 million toll on the pear industry each year in the Pacific Northwest.

"We're looking at an integrated control program for the rot, and yeasts could play a big part," said David Sugar, a plant pathologist at OSU's Southern Oregon Research and Extension Center.

"Most rots start at tiny injuries in the fruit during harvest and handling. If we can get beneficial yeast cells on the fruit before harvest and injury, they might protect the fruit."

Sugar said untreated pears have several hundred yeast cells per fruit. With yeast sprays, he and OSU graduate student Jesse Benbow have been able to boost that number to a million cells per fruit.

More good news - the cells survived at least three weeks in hot, summer heat, long enough to reduce incidences of rot.

Yeast sprays can't completely prevent rot. Sugar said producers will also have to use high-carbon dioxide storage of the pears and other techniques.

"Our research shows the combination of high carbon dioxide and low oxygen also keeps rot from developing," he said.

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David Sugar, 541-772-5165