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               Boxelder bugs, Boisea trivittatus, are familiar insects to most people. They are generally not noticed during summer, but often can become an issue when they try to move into homes during fall as they search for overwintering sites.

 

Identification

               Adult boxelder bugs are about 1/2-inch long, black with orange or red markings, including three stripes on the prothorax, the area right behind the head. Their wings lay flat over their bodies, overlapping each other to form an ‘X’. The immature nymphs are 1/16th-inch long and bright red when they first hatch. As they grow older and become larger, they are red and black. You can potentially see all stages at any given time during the summer.

 

 

 

 

 

 

 

Biology and life cycle

               during spring as the weather starts to warm up. Adults feed on low vegetation and seeds on the ground during spring and early summer, and begin mating a couple weeks after they started feeding. Starting in mid‑July, they move to female seed-bearing boxelder trees where they lay eggs on trunks, branches, and leaves. They are rarely found on male boxelder trees. Boxelder bugs may also feed on maple or ash trees. There is no noticeable feeding injury to these trees. During years of high populations, you may find nymphs on the ground or in gardens feeding throughout the summer.

During late summer and fall, boxelder bugs start to leave the trees from where they were feeding to find protected areas for the winter. Although nymphs may be present in the fall, only fully grown adults survive the winter. Adult boxelder bugs typically can fly several blocks, although in some cases they can travel as far as two miles.

 

               As the weather cools, boxelder bugs push into cracks and spaces around homes. In some cases they end up in the interior of buildings where they are often found around windows. They remain active until it becomes cold, which could continue into winter when the weather is mild. While you may see persistent numbers of these bugs, individuals are short-lived, only surviving for a few days up to a week. Other boxelder bugs end up in sheltered areas in walls, attics and similar areas where they remain until it warms up.

 

               During winter, boxelder bugs are generally inactive. However, during mild, sunny days, boxelder bugs become mobile with the increased temperature. They enter a home’s interior from overwintering areas within the home, e.g in walls or attics. As they wake up, they follow the warmth into the home's living quarters. Once there, they typically move towards windows and other sunny areas. However, the warmth does not reach the insects equally and they do not all become active at the same time.

 

  

 

Management

 

 

Outdoors

 

               The best management of boxelder bugs is prevention -- take steps to keep them from entering your home from the start. You can partly do this through exclusion though it largely depends on how your home was constructed. Make any repairs by the end of August.

 

For all homes

 

• Repair or replace damaged window and door screens.

• Repair or replace damaged screens in roof and soffit vents, and in bathroom and kitchen fans.

• Seal areas where cable TV wires, phone lines, and other utility wires and pipes, outdoor facets, dryer vents and similar objects enter buildings.

• Seal with caulk or for larger spaces use polyurethane expandable spray foam, copper mesh, or other appropriate sealant.

• Install door sweeps or thresholds to all exterior entry doors. Install a rubber seal along the bottom of garage doors.

 

For homes constructed of stucco, plaster, stone or brick veneer

 

• Check the outside surfaces for spaces and cracks that may allow insects easy entry, sealing any openings 1/8th inch in size or larger. This will not eliminate all boxelder bugs but it can significantly reduce the number entering buildings.

• Seal cracks and spaces around doors, windows, roof lines, and fascia boards and other areas where vertical surfaces meet horizontal ones.

• Also check for gaps and cracks where different materials meet, such as brick and wood siding. Seal cracks with caulk, such as silicone, elastomeric latex, or silicone/acrylic.

• For stone or brick veneer, the bottom of the walls will have ‘weep holes’ and these must not be sealed up. Instead, visit a local hardware store and request ventilation plugs that can be installed in these weep holes.

 

For homes constructed of vinyl siding

 

• Unfortunately, houses with vinyl siding provide too many gaps to effectively exclude these insects. These houses are designed for aesthetics, durability, and energy efficiency. Relative to excluding insects, the benefit of these houses is that they are often effectively sealed with a ‘house wrap’ placed underneath the siding.

• For these types of houses, concentrate on the recommendations provided for all houses and use an insecticide on areas where these bugs have congregated in the past. In our experience, large numbers collecting around the doors and other entryways are often the most prevalent means of entry during the fall. For information on insecticide use, see the section below.

 

Indoors

 

               Once boxelder bugs are found the best option is to physically remove them with a vacuum or a broom and dust pan. If this occurs during fall, check around the building exterior because they can often be found congregating in sunny or warm areas. If they are close to entrances, an insecticide may be required to prevent their entrance into a home.

 

               Inside homes, insecticides have limited value and are not usually suggested. Remember that when boxelder bugs are active, they do not live indoors much more than a few days and do not reproduce inside. When they are emerging from the walls and other sites where they have been dormant during the winter, spraying insecticides does not prevent more from returning.

 

Spraying or Removing Trees

 

               Spraying or removing the seed-bearing boxelder trees in your yard is not a practical solution for boxelder bug management because adult boxelder bugs can fly up to a couple miles from food. Also, boxelder trees (as well as maple and ash) are usually common providing many potential sources of boxelder bugs. In our opinion, the benefits of having these trees in a landscape outweigh the problem of occasional infestations. Remember that although you may encounter large numbers of boxelder bugs in a given year, they are not automatically abundant every season.