Minnesota's outdoors enemy No. 1 usually is the mosquito. But since frost has dispatched the mosquito another insect now tops the list.
Asian lady beetles are everywhere these days. Walk outdoors and they cling to your clothing. Sunny sides of buildings are plastered with them.
Weather triggered the invasion. Frost tells beetles it's time to hibernate. Warm fall days are when they seek shelter. In their native China the beetles winter on cliffs and other rock outcroppings. There's not much of that in central Minnesota, so they choose buildings instead.
Why so many beetles this year?
Jeff Hahn, an entomologist at the University of Minnesota, said he isn't sure if the population is higher this year or if it's just a case of ideal fall weather causing them to concentrate in greater numbers.
"Last year after the temperature first dropped to freezing it never dramatically warmed back up," Hahn said. "Lady beetles still moved into buildings, but unlike this year we never really seemed to have that one defining moment when they first started to enter."
If beetles are scoping out your house for hibernation, now's the time to send 'em packing. Caulk and seal openings that might provide entry, such as windows, doors, roof lines, along the foundation and where utility lines enter the house. Apply insecticide to surfaces where the beetles are found en masse.
"Once they get in your home your options are limited," Hahn said. "The only real control is to vacuum them and then discard the bags. Avoid crushing them, as this can stain surfaces."
If beetles are out of control at your house then hire an exterminator. "They have access to products that aren't available to homeowners," Hahn said. "Demand CS, for example, is particularly effective against lady beetles."
Asian lady beetles were introduced in the southern U.S. to control aphids, small insects that feed on plants. They migrated north and were first found in Minnesota in large numbers in about 1998. They're larger than their cousin, the lady bug.
In summer the beetles live in fields, trees and on the ground, where they feeds on aphids.
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