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OMAHA, Neb. (AP) — Bug experts say Japanese beetles and pirate bugs are just too well adapted to Midwest winters to die off.

Donald Lewis, a professor of entomology at Iowa State University, told the Omaha World-Herald that the bugs can survive in zero or below zero temperature. Dramatic temperature swings may temporarily slow the spread of the tiny pests, Lewis said.

“In general, what would reduce overwintering populations the best is if it got really, really cold, and then suddenly got really, really warm, like 40 degrees or 50 degrees, but then it went freezing again,” Lewis said.

The winter of 2013-14 saw a dry fall and a prolonged period of soil freezing that lowered the Japanese beetle population for the summer of 2014, Lewis said. But the population dip didn’t last.

“By the summer of 2015, they were back, and by the summers of 2016 and 2017, we had large numbers again,” Lewis said.

Such temperature changes could also harm the bugs’ predators and beneficial insects, said Jody Green, an entomologist for the University of Nebraska at Lincoln Extension.

Pirate bugs go into a resting state in the winter that allows them to resist freezing and death, Green said.

“I don’t think this cold now will guarantee (that) Japanese beetles or pirate bugs will be lessened,” she said.

Lewis said Japanese beetles lay eggs that hatch into grubs that are 6 inches deep in the ground, protecting them from cold air. Even when the ground freezes, he said, the grubs are protected from ice formation by a small amount of antifreeze in their bodies.

The quarter-inch bugs, identified by their green head and five white tufts of hair on each side of their abdomen, are known to target as many as 300 species of plants.


Information from: Omaha World-Herald,