Boxelder Bug

Bruce Barrett
Department of Entomology

The boxelder bug is a pest around the home in late summer. This bug is about 1/2 inch long and 1/6 inch wide. Black with three red lines on the thorax, it has a red line along each side and a diagonal red line on each wing. The wings lie flat on the back when at rest.

Feeding habits

Boxelder bugs normally feed on leaves, flowers and seed pods of boxelder trees and other trees of the maple family, particularly the silver maple. These bugs cause little damage to trees.

They may number into the thousands on some trees, usually on the female or seed-bearing trees. They also may be on male boxelder trees and other trees and plants.

Life cycle

The overwintering bugs lay eggs in the spring. Small reddish nymphs hatch from these eggs and develop into adults during the summer. The adults mate soon after reaching maturity, and the females lay eggs for the second-generation bugs.

These nymphs mature in August and September and cause concern to homeowners by congregating in large numbers on trunks of host trees. However, greatest concern usually is during the fall when the adult bugs congregate on the south side of structures and then enter in search of winter hibernation quarters. They hide in small cracks and crevices in the attic, walls, doors and window casings. They also may hide under siding and under trash around the foundation of the home and even in leaves left in gutters.

During warm winter days and in early spring, they are a nuisance as they crawl or fly in the home. They produce no odor, nor do they damage or injure wood, cloth, fruits, vegetables, humans or other animals.

Control

Boxelder trees are the chief source of food for boxelder bugs, so homeowners might benefit by removing these trees, especially the female or seed-bearing trees. The same strategy may apply to silver maple trees. Also, don't plant or allow these trees to become established. Take the following preventive measures if you don't want to remove the trees:

Place screen wire inside the vents in the attic and eaves.
Repair and caulk places where bugs may enter the home, such as cracks around doors, windows and siding and in the foundation.
Eliminate hiding places such as piles of rocks, boards, leaves and general debris close to homes.
Rake leaves, weeds and grass from a strip 6 to 10 feet wide around the foundation, particularly on the south and west sides of the structure. Such a barrier strip discourages congregation of bugs near the foundation.

Spray recommendations outside homes and buildings
When concentrations of boxelder bugs are seen, either on the trunks of boxelder trees or on the foundation and sides of a building, apply a spray directly on the bugs and on the area where they are observed. Use any of the insecticides listed in Table 1.

Check the label on the insecticide container to make certain both the insect and the site are listed before using.

Thoroughly apply a residual spray of any of the insecticides to the surface of the barrier area and to the foundation and sides of the buildings. This will help control individual boxelder bugs and other migrating insects. Additional spray applications may be needed.

Spray recommendations inside homes
Control boxelder bugs that come through the walls into the heated rooms of the home by hand-collecting, fly swatter, vacuuming, or using a household aerosol containing pyrethrins, resmethrin, or other materials labeled for this use.

Table 1
Insecticides for boxelder bug control.

Insecticide	Some trade names	Remarks
azadirachtin	Neem oil	Botanical insecticide.
carbaryl	Sevin	Outdoor use only.
chlorpyrifos	Dursban	Outdoor use only.
cyfluthrin	Tempo, Decathlon	For use only by PCOs¹. Outdoor use only.
diazinon	Diazinon	Outdoor use only.
endosulfan	Thiodan	Outdoor use only.
lambda-cyhalothrin	Scimitar	Restricted Use Pesticide. For use only by PCOs. Outdoor use only.
malathion	Malathion	Outdoor use only.
pyrethrins	numerous brands	Botanical insecticides; fast knockdown; indoor and outdoor use.
tetramethrin, permethrin	numerous brands	Synthetic pyrethroids (pyrethrin-like insecticides); fast knockdown; indoor and outdoor use.

¹PCO = Licensed pest control operators (someone licensed to apply pesticides).

Caution
Handle insecticides with care. Follow directions on the label. Keep insecticides off skin and out of eyes, nose and mouth. Wash immediately with soap if concentrates are accidentally spilled on skin and after completing spray application. Store unused insecticides in a dry area, out of reach of children and pets.

Darryl P. Sanders, emeritus state entomology specialist, Department of Entomology, was the original author of this publication.

G7360, reviewed August 1999