Asian beetles return to state this spring

Although they bug some Minnesotans, the insects control other pests.

Ed Swaray

Last spring, Asian lady beetles invaded William Bombo’s Crystal, Minn., apartment, much to his disgust.

“Seeing those creepy insects in my room makes me sick,” the economics junior said.

But the insects that annoy Bombo make good research material for Robert Koch, a University graduate student.

Last winter, while researching the temperatures necessary to keep the Asian beetles alive Koch bought hundreds of the bugs at $33.75 per hundred.

“These insects are commercially available,” he said. “Some companies raise them because they are biological control agents against aphids and other soft-bodied insects.”

Whether help or hindrance, Asian beetles are returning to Minnesota this spring, said Jeffrey Hahn, entomology professor with the University’s Extension Service.

Temperatures around 30 to 40 degrees bring the return of the beetle, Hahn said.

“Mild, sunny winter can wake these dormant insects,” he said. “When spring arrives they move outdoors.”

Hahn said the Asian lady beetles do not damage homes or property but they might pinch, bite or secrete foul-smelling, yellowish liquid as a defense method when threatened.

“Repeated exposure to dead lady beetles can cause allergic reaction in some individuals,” he said.

People can take several measures to prevent Asian lady beetles from entering homes, Hahn said. They include sealing cracks and spaces through which the beetles enter the house and using black light traps to capture them after they enter.

Once they get in a house, however, Hahn said there are not many ways to get rid of them.

Last spring, Bombo said, he used insecticide in his room to rid it of beetles and he’s bracing himself for their return this year.

“I hate those damn beetles and I will do everything to get rid of them,” he said.

Koch, however, said he does not recommend using pesticides because of human exposure risks.

The U.S. Department of Agriculture first released Asian lady beetles in California in 1916 as a biological control agent against pecan aphids, Hahn said.

Over the years, the department released beetles in other states. Although they were never released in Minnesota they were first spotted in the state in 1995. By 2000 they had dispersed throughout Minnesota, Hahn said.