University of Maryland Extension

Boxelder Bugs

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black and orange boxelder bug
Boxelder bug. Photo: William M Ciesla Forest Health Mgmt International, bugwood.org

The Boxelder Bug is a common pest of boxelder trees and a nuisance pest in and around homes. Adult bugs are oval in shape and about 1/2 inch long when fully grown. They are dull black with red markings along the edges of the front wings. The immature bugs, called nymphs, are red with black legs and wingpads. Nymphs in early stages of development can be completely red. Adults and nymphs in various stages are often found together.

The bugs feed primarily on female boxelder trees, which can be identified by their compound leaves and winged seed pods. The seed pods are noticeable when they turn brown in the fall. These trees should be removed if they are near the home. The boxelder bugs tend to swarm on sunny exposures of homes in the fall. They prefer white surfaces on the south side of buildings. They hide in cracks during cold weather and may find their way indoors.

congregation of boxelder bugs on a leaf
A cluster of boxelder bugs on a hosta leaf

a boxelder tree and seed pods
Boxelder tree seeds (samaras)

life stages of boxelder bugs
The different life stages of a boxelder bug

boxelder bugs on a tree stump
Boxelder bugs congregated on a stump

Management

Seal up cracks with caulk, tighten screens and doors and replace weather stripping to prevent entry. Vacuum up any bugs found in the home. Boxelder bugs on houses can be knocked down with a forceful spray of soapy water. Do not use detergent, it can damage plants. If plants are near the home use insecticidal soap. Test the insecticidal soap on an inconspicuous part of the house to make sure it won't damage the finish.

Additional Resource

Publication: (PDF) HG 10 Boxelder Bug

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