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Oregon Pears

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Fighting pests with basic instincts

Oregon pears. We know them from calendar-art landscapes of snowy-white orchards and from world-famous mail-order delicacies. With their Rubenesque shapeliness and their buttery-smooth flesh, pears are said to be best enjoyed while you soak in a warm tub and let the juice drip.

With such a seductive fruit, it may not surprise you to learn that Oregon pear growers are using seduction in the orchard to combat some of the worst pests that threaten pears. One strategy is to mimic a codling-moth singles bar and trap the love-struck male moths as they venture in.

Rick Hilton
OSU entomologist Rick Hilton deploys several strategies for controlling pests in pear orchards, including pear ester traps that he places in trees (above) and pheromone “puffers” that disrupt the mating activity of coddling moths (below). Photos by Lynn Ketchum.

Sex pheromones are the perfumes created by eligible female moths. By luring male moths to the wrong neighborhood with synthetic pheromones, growers foil the male’s attempt to locate a female and mate. Such mating disruption leads to fewer baby codling moths, the larval “worms” that infect wormy pears and apples. It also helps growers predict when the successful males’ offspring will emerge, so they can pinpoint when and where to apply chemical controls.

Such “integrated pest management” (IPM) uses cleverness before chemicals. Researchers at the OSU’s Southern Oregon Research and Extension Center have perfected this and other IPM strategies to combat insect pests that feast on Oregon pears. As a result, in the last 10 years, IPM techniques have led to an almost 80 percent reduction in the use of chemical pesticides in southern Oregon orchards.

“These results were achieved by using a combination of strategies, including mating disruption, targeted insect pathogens, and a natural clay material to repel pests,” said Richard Hilton, an entomologist at the research and extension center.

deploying puffer

But back to seduction. The latest technique the researchers are testing is to infuse a trap with the fragrance of fully ripe pears, which are hotspots for codling-moth nightlife. Traps emit a synthetic pear aroma to attract both male and female codling moths looking for a good time, luring them into a trap with no exit.

Although the pear ester traps catch fewer moths than sex pheromones, they help researchers monitor the sex life of moths, especially to predict the moment when females begin to lay eggs. By monitoring the number of females in the traps, correlating the day’s temperature, and sampling fruit throughout the growing season, growers can predict when moth eggs will hatch and the damaging larvae emerge. With precise powers of prediction, growers can avoid unnecessary spraying throughout the season and accurately target a single application of pesticide only when and where it is needed.

And it turns out that the aroma of ripe pears also attracts larval codling moths, and may be used to lure the caterpillars away from real fruit and into fruit-flavored traps, offering pear growers another strategy in integrated pest management.