Fall Visitors

6 October 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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With fall weather settling in we are starting to welcome some of our insect friends who are seeking a place to spend the cold winter days and nights. Most of you are familiar with our friend the multicolored Asian lady beetle because you are used to hosting them for the winter. While it is still early for them to appear, we are already seeing other insects in homes such as leaf-footed bugs, boxelder bugs, Polistes wasps, and brown marmorated stink bugs. Most of these insects have been a harbinger of fall for many years. The stinkbug species is relatively new to central Virginia.

The brown marmorated stink bug was apparently accidentally introduced into eastern Pennsylvania sometime during the 1990s. It was first collected in September of 1998 in Allentown, PA but probably arrived several years earlier.

This true bug in the insect family Pentatomidae is known as an agricultural pest in its native range of China, Japan, Korea and Taiwan. It becomes a nuisance pest both indoors and out when it is attracted to the outside of houses on warm fall days in search of protected, overwintering sites. It occasionally reappears during warmer sunny periods throughout the winter, and again as it emerges in the spring.

Adults are approximately 17 mm long (25 mm = one inch) and are shades of brown on both the upper and lower body surfaces (Fig. 1). They are the typical shield shape of other stink bugs, almost as wide as they are long. To distinguish them from other stink bugs, look for lighter bands on the antennae and darker bands on the membranous, overlapping part at the rear of the front pair of wings. They have patches of coppery or bluish-metallic colored punctures (small rounded depressions) on the head and pronotum (the area behind the head). The name stink bug refers to the scent glands located on the dorsal surface of the abdomen and the underside of the thorax.

We do not know whether this species will become an agricultural pest in Virginia. In its native range, it feeds on a wide variety of host plants. Fruits attacked include apples, peaches, figs, mulberries, citrus fruits and persimmons. This true bug has also been reported on many ornamental plants, weeds, and soybeans. Feeding on tree fruits such as apple results in a characteristic distortion referred to as cat facing, that renders the fruit unmarketable.

Even though these insects do not harm humans and do not reproduce inside structures such as houses, they cause concern when they become active and conspicuous in fall and spring. If many of them are squashed or pulled into a vacuum cleaner, their smell can be quite apparent.

Before Bugs Enter a Building: Mechanical exclusion is the best method to keep stink bugs from entering homes and buildings. Cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath the wood fascia and other openings should be sealed with good quality silicone or silicone-latex caulk. Damaged screens on doors and windows should be repaired or replaced.

After Stink Bugs Have Entered the Structure: If numerous bugs are entering the living areas of the home, attempt to locate the openings where the insects gain access. Typically, stink bugs will emerge from cracks under or behind baseboards, around window and door trim, and around exhaust fans or lights in ceilings. Seal these openings with caulk or other suitable materials to prevent the insects from crawling out. Both live and dead stink bugs can be removed from interior areas with the aid of a vacuum cleaner.

It is not advisable to use an insecticide inside after the insects have gained access to the wall voids or attic areas. Although insecticidal dust treatments to these voids may kill hundreds of bugs, there is the possibility that carpet beetles will feed on the dead stink bugs and subsequently attack woolens, stored dry goods or other natural products in the home. Although aerosol-type pyrethrum foggers will kill stink bugs that have amassed on ceilings and walls in living areas, it will not prevent more of the insects from emerging shortly after the room is aerated. For this reason use of these materials is not considered a good solution to long-term management of the problem. Spray insecticides, directed into cracks and crevices, will not prevent the bugs from emerging and is not a viable or recommended treatment.

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.