By: Wizzie Brown
Boxelder bugs, Boisea trivittatus, and red- shouldered bugs, Jadera haematoloma, feed on several kinds of trees. In the fall, when temperatures drop, these bugs move to protected areas such as under shingles or siding, around doors and windows, or in cracks and crevices in foundations.
These bugs can become a nuisance when they enter homes or other structures seeking shelter. If many of them move into a home, their excrement can stain curtains, furniture, walls, and other surfaces.
Adult boxelder bugs are about 1/2 inch long and 1/3 inch wide. They are dark brown to gray or black with three distinctive red or orange lines running length- wise on the pronotum (the area behind the head). The overlapping wings are folded over the back of the body and red lines mark the outer edges of the wings (Fig. 1).
The immature stages, or nymphs, of boxelder bugs are shaped like the adults but are smaller and their wings are not fully developed. The nymphs are bright red and develop black markings and wings as they mature (Fig. 1).
The red-shouldered bug (Fig. 2) is oval and about 1/2 inch long. It is brownish gray with red eyes and markings on the outside edges of the pronotum.
Red-shouldered bugs, like boxelder bugs, feed on the seeds of boxelder trees and the fruits of other trees.
With higher spring temperatures, boxelder and red-shouldered bugs emerge from overwintering sites and begin mating a few weeks later. Females deposit eggs on leaves, grass, rocks, or tree bark. After about 2 weeks, the eggs hatch and the nymphs develop into adults during the summer. Because of the timing of the spring emergence in Texas, there can be two or more generations each year with several stages of nymphs and adults present at the same time.
In the fall, adults and nymphs leave their host trees to look for sheltered areas for overwintering. Usually only the adults survive the winter. Often, large numbers of bugs congregate on houses or buildings, especially on southern or western exposures to warm themselves in the sun.
As temperatures drop, the bugs move into tree holes, cracks and crevices around door and window casings, foundations, and walls. Sometimes they move indoors to warm areas of a building and eventually move toward windows or other sunny areas.
Boxelder bugs feed primarily on the seeds of female boxelder trees. Minor host plants (plants from which they obtain food) include apple, ash, cherry, chinaberry, grape, maple, peach, plum, and western soapberry trees. Red-shouldered bugs feed on althaea, arborvitae, bluebonnets, ficus, Goldenrain tree, western soapberry, and others.
Although the bugs suck plant juices while feeding, they seldom gather in enough numbers to harm the trees.
Removing host trees may help eliminate a breeding location, but the insects can fly in from neighboring areas that contain host plants. If you do want boxelder trees in your yard, it may help to plant only male boxelder trees.
Prevention helps keep boxelder bugs from moving into a house. Inspect the outside of the structure for any areas that could be suitable over- wintering sites for boxelder bugs. Take exclusionary steps, preferably before August.
Preventive actions include:
• Seal cracks and crevices with sealant.
• Seal the areas where pipes or wires enter the structure with sealant.
• Stuff weep holes with copper mesh or plastic screening made specifically for weep holes (kits are available).
• Repair or replace any damaged window screens.
• Replace damaged weatherstripping around doors and windows. If you can see daylight around doors when they are closed, replace the weatherstripping.
• Install a door sweep on exterior doors and a rubber seal along the bottom of garage doors.
• Install new or repair damaged screens or soffit vents in the attic, roof, and eaves.
• Remove and dispose of the seeds that can become food for the bugs.
• Eliminate hiding places such as piles of boards, leaves, rocks, and general debris near the house.
As the bugs aggregate in the fall, handpick or vacuum them up with a handheld vacuum. Dispose of them in the garbage.
Apply pesticides to hibernation areas such as fences, building foundations, sides of houses, tree leaves and trunks, and other outside areas where the bugs congregate. Look for active ingredients such as cyfluthrin, deltamethrin, esfenvalerate, insecticidal soap, malathion, neem, and pyrethrin.
Jared Ripple, Extension Agent–Integrated Pest Management; Molly Keck, Extension Program Specialist; and Bastiaan Drees, Professor and Extension Entomologist reviewed this publication.
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