Battling Boxelder Bugs

BIOLOGY. The favorite host for this insect is the boxelder tree, Acer negundo, especially the female tree, which bears the seed pods. This insect may also feed on other trees in the maple family, including sugar and silver maples. The boxelder bug has sucking mouthparts, and adults and nymphs feed on the plant sap in leaves and seeds.

Stages in the boxelder bug’s life cycle include egg, nymph and adult. Nymphs look similar to adults but lack fully developed wings and do not mate. In spring, female boxelder bugs lay eggs in crevices of tree bark and leaves of the boxelder tree. Eggs may also be deposited in hibernation sites, such as stones, grass, paper litter, fences and doorway crevices. Eggs are yellow when laid and become dark red within several days. Egg incubation period is about 10 days, and the small nymphs begin feeding on plant tissue almost immediately after hatching. There are five nymphal stages before the adult, and development from egg to adult takes about 60 days. There are two boxelder bug generations per year in the eastern, southern and western regions of the United States and usually one generation per year in the North. What follows is a description of the boxelder bug life cycle:

April and May. During spring, adults and nymphs can be seen emerging from hibernation sites, flying to a host tree or gathering on the sides of buildings. At this time the overall size of boxelder bug infestations on trees and buildings can be considerable smaller (differing as much as tenfold) than infestations in the fall. Females emerging from hibernation begin to lay eggs in April and May.

The temperature of surfaces found around buildings can contribute to infestations of adult boxelder bugs in the spring and fall. Research data, obtained by measuring the body temperature of boxelder bugs and the temperature of different surfaces, shows that these bugs prefer surfaces with temperatures that are much higher than their normal body temperatures.

June and July. In late spring and early summer boxelder bug nymphs that hatched from the eggs, and adults that survived the winter, usually move from the sides of houses to shrubs and ornamental trees.

September and October. In fall there is an increase in the number of boxelder bugs on host trees, and this increase is associated with development of the ovules on female boxelder and maple trees. There are much fewer boxelder bugs around buildings in the fall; most are found on trees. Adult boxelder bugs move to overwintering sites during October. Although the same overwintering sites are not usually used every year, there are some that are frequented on a regular basis.

November to March. In fall and winter months boxelder bugs travel short or long distances (as much as two miles) from a host tree to a favorable hibernation site. They spend the winter in leaf litter next to buildings, under bark in protected areas or in other spaces in which large numbers of boxelder bugs can gather for a few months.

CONTROL PROBLEMS. Chemical control of boxelder bugs is usually based on the application of residual insecticides to outside surfaces of infested buildings, and limited application indoors. There are a few problems associated with applying insecticides to outdoor locations in which boxelder bugs gather in large numbers. Although these insects are attracted to the sunlit side of houses and other buildings, insecticides applied to these areas may be adversely affected by the sunlight. Insecticides exposed to sunlight may have a short period of effectiveness, because sunlight can speed up the natural degradation process.

Surfaces such as brick and concrete block, latex-painted and bare-wood siding on the outside of a building can influence the effectiveness of residual insecticides. They can absorb some of the insecticide applied to them and limit the amount available to kill boxelder bugs that walk on the surface.

In addition to sunlight and absorbing surfaces, professional pest control operators may have problems contacting with insecticide all the boxelder bugs gathered in harborges. These insects disperse rapidly when disturbed. Insecticides applied directly to large groups of boxelder bugs can cause them to scatter, and some may not be contacted with the liquid spay. Several spray applications may be necessary to control large infestations around houses or commercial buildings.

CHEMICAL CONTROL. Five insecticides were evaluated for boxelder bug control: cypermethrin (Demon WP), chlorpyrifos (Dursban LO, ME), bendiocarb (Ficam Plus), diazinon and propetamphos (Safrotin). The insecticides were applied to latex-painted plywood panels. The panels were treated to run off. There was more than 95 percent mortality of the boxelder bugs placed on the treated panels one day after application of cypermethrin, bendiocarb, diazinon and chlorpyrifos. Dursban ME provided 57 percent mortality at one day after application. At seven days after application, cypermethrin provided 67 percent mortality; the other insecticides provided about 50 percent mortality.

Karen M. Yoder is with the West Virginia Department of agriculture and William H. Robinson is with the Urban Pest Control Research Center at Virginia Polytechnic Institute and State University.