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Student entomologist stalks predators to save Washington apples

Robert Orpet in an orchard with a cardboard earwig trap
Student entomologist Robert Orpet used cardboard to catch and count earwigs in central Washington apple orchards, revealing that the insects could be important predators (WSU photo).

White, fuzzy, and about the size of a pencil tip, the woolly apple aphid is a persistent pest in Northwest apple orchards, harming trees and shrinking apple harvests.

Robert Orpet, doctoral student at Washington State University’s Tree Fruit Research and Extension Center, knows that farmers have a hard time getting rid of this tiny pest. Instead of frequent spraying, he has a better idea: Why not use a good bug to get rid of a bad one?

That’s how Orpet found himself counting earwigs in Central Washington’s apple country.

Predators’ punch

Originally from the Midwest, entomology student Orpet brought his curiosity about insects to WSU, where he works directly with Washington’s $2.4 billion apple industry to study biocontrols—insect predators that eat pest bugs.

Beneficial insects reduce the need for pesticides, saving farmers money and ensuring healthy produce that’s high in consumer demand.

“Farmers love biological controls,” Orpet said. “They love to see predators in action, eating their pests and improving their bottom line.”

Bugs as thick as snow

The tiny woolly apple aphid gets its name from the coat of cottony fibers sported by adults. Woolly apple aphids feed on the roots and branches of apple trees, stealing nutrients and water and causing galls, or abnormal growths. Worse, infestations can decrease tree growth and keep fruit from developing, while the aphid’s sticky honeydew secretions can bring on fungal infections.

A large colony of woolly aphids clings to an apple branch
About the size of a seed, tiny woolly apple aphid can amass in snowy, fluffy, meter-long colonies, harming apple trees and preventing fruit development.

Aphid colonies are invisible when they feed on tree roots. But when adults emerge onto the branches, they’re highly visible thanks to their woolly coats.

“In bad years, infestations make apple trees look like they’re covered in snow,” Orpet said. “That’s when growers really take notice.”

Growers have difficulty managing woolly aphids with insecticides, and must spray often to keep numbers down. Well-known predators like ladybugs and lacewings could take a bite out of the woolly aphid population, but Orpet wanted to know if a different insect is making a difference: The humble earwig.

Earwig round-up

With its prominent tail pincers, wriggly body and habit of hiding in our favorite fruit and flowers, the earwig is a familiar but often alarming little bug to the casual observer.

“Earwigs are unappreciated predators,” said Orpet. “Apple pickers don’t like them, because they have a tendency to hide in apple clusters. They’ll eat anything, and some growers wonder if they cause damage themselves.”

Working with managers at four different commercial orchards, Orpet set about catching earwigs with cardboard traps. Active at night, earwigs hide by day in tight spaces. Corrugated cardboard sheets are a perfect shelter, so Orpet could easily shake them out and count them.

Sectioning off orchards, Orpet removed earwigs in some places, adding them at others. In every site, he counted woolly aphid colonies and each infested wound.

“There was an obvious difference,” Orpet said. “There were fewer aphid colonies in places where I released earwigs.” He found no evidence that earwigs were causing damage themselves, but captured video footage of earwigs eating aphids and destroying their colonies.

Earwigs in demand

Orpet is excited about the potential of biocontrols to protect our environment, improve safety, and improve orchard yields and profit. While more studies could be done on how earwigs affect fruit, growers should consider the insect a valuable predator.

“Washington apple growers are interested in research-based recommendations and innovations, and I’ve already had farmers asking me where they can buy earwigs! They want to see if these insects can help with their aphid problems.

“Unfortunately, I’m not aware of anyone selling earwigs,” he added.

As one of the few insects that care for their young, Orpet sees earwigs as both beneficial and fascinating.

“They’re charismatic and beautiful creatures,” he said. “I’ve always been a fan!”