Box Elder Beetle
(Boisea trivittata)

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Although Box Elder Beetles don’t cause significant damage to structures, they can become a nuisance.

Appearance
 
  • Dark brown or black with red lines along the thorax and sides

  • Their wings are flat and red

  • Nymphs are bright red

  • They are 11 -14 mm in length

  • Release pungent bad-tasting compound when disturbed

Behavior, Diet & Habits

You can find Box Elder Beetles nesting on boxelder, maple, and ash trees during the warmer months. In winter they migrate to homes and buildings for shelter. They enter through cracks and crevices, find a nesting spot, and hibernate through the cold season. They stay in the warmest areas and emerge by heat sources. Box Elder Beetles are considered a nuisance pest since they don’t cause significant damage to buildings. However, their droppings leave stains on linens and furniture.

In the Spring, adult beetles congregate in groups, also called aggregations, and find a host plant where they can live and breed. They eat leaves, flowers, twigs, and pierce plant tissue to extract juices, causing minimal damage to the host tree.

Reproduction

The eggs of Box Elder Beetles are yellowish to reddish brown in color, which camouflages them in the bark of the host tree. A few days later the eggs hatch and nymphs grow through six stages before becoming adults to begin the breeding process again.

Signs of an Infestation

The largest sign on an infestation is a congregations of adult box elder beetles on the sunny wall of a building in the fall.

Treatments

Prevention starts with sealing cracks and crevices to block entry into structures. When planting boxelder trees, choose male trees since the female trees are seed-bearing and more susceptible to infestation. To treat them, have an experienced pest control company assess and use proper chemicals. This will stop them from multiplying.