Invasive insect pests: Watch for these unwanted guests

With the end of summer approaching, homeowners may start noticing some unwanted house guests. There are a number of pests that will be looking to invade homes during the cooler months, according to University of Illinois Extension horticulture educator Andrew Holsinger.

The most common are multicolored Asian lady beetles, boxelder bugs, and brown marmorated stink bugs.

The south and west sides of the home are more popular locations for these insects to congregate. As the weather outside cools, the warmth of the home makes it an attractive spot for these insects. They can enter in large numbers and reside in the cavities of walls, attic spaces, and even to the depths of a basement.

“Prevent beetles and other insects from entering the home by caulking or sealing cracks and crevices,” Holsinger said. “Insects often find areas like these in nature to overwinter and will use your home as a substitute.”

Holsinger said that you can seal obvious cracks and openings, but you still may encounter some of these insects intruding in your space. However, these insects are not harmful in terms of spreading human disease.

“The insects that find their way into your home in the fall are mostly just a nuisance,” he said. “They can be problematic for certain individuals who can have an allergic reaction or asthma triggered by their presence.”

Multicolored Asian lady beetles: The Asian lady beetles are oval or convex in shape and yellow to red in color. The number of spots on Asian lady beetles may vary. The head is usually concealed beneath the disk-shaped pronotum, which is cream to yellow with a black "M" design in the center. The beetles can bite, but do not draw blood. They have a defensive chemical, which is foul-smelling and can stain if the beetle is disturbed or crushed.

Boxelder bugs: Boxelder bugs are native and are noted as avid home invaders. They are black with red or orange edges on the wings. They are about a half inch long and have the appearance of a red "V" on their back. The easiest way to identify them are the three stripes behind the head (prothorax). Boxelder bugs are some of the most tolerable in the home as they do not bite and aren't as intrusive guests/pests as others can be.

Brown marmorated stink bugs: Brown marmorated stink bugs are another odor-emitting insect when hit or smashed. Look for the white bands on the antennae. The adults have the typical "shield' shape of all stink bugs. As brown marmorated stink bug populations increase in an area, they become more of a nuisance in homes and buildings.

Other insect invaders may enter into homes and look similar to the brown marmorated stink bug, including spined soldier bug, common brown stink bug, and western conifer seed bug.

Exclusion is the recommended strategy for keeping invading insects from entering homes and buildings. “Don’t forget about damaged screens that may need to be repaired or replaced,” Holsinger said.

Insecticides are not recommended for treating the interior of homes to combat these unwanted guests. Instead, use a vacuum to capture them. Insecticides may be used as a preventive measure on the exterior of buildings to manage populations before they have the opportunity to enter. Be sure to follow all insecticide label instructions.