[Tech Talk] Occasional Invaders - What's all the fuss about?

Columns - Technically Speaking


July 27, 2011

For homeowners, invading insects are a nuisance. For food-processing plants, they can be a source of product contamination. For restaurants, they are a nuisance to customers and can contaminate the food being served. Also, they often invade in massive numbers and some release a pungent odor when disturbed. Others impart an unsightly stain when smashed or crushed on a surface, and some will bite and/or can cause allergic reactions.

Which insect? Key identification features of overwintering pests are as follows:

1) Boxelder bugs (Boisea trivittata) and western boxelder bugs (B. rubrolineata). About 3/8- to 5/8-inch long, their reddish marks are distinctive (western boxelder bugs in addition have thin lacy red lines on front wings). Their fecal material may cause a red stain, they can emit a pungent odor if roughly handled and may "bite" on occasion.

2) Brown marmorated stinkbugs (Halyomorpha halys). About ½-inch long, they have a large triangular plate on their back, and broad whitish bands on outer two antennal segments. They emit a pungent odor if roughly handled.

3) Cluster flies (Pollenia spp.). About 3/8-inch long, their thorax (middle portion to which legs and wings are attached) has many short crinkly yellow or golden hairs (which may be lost in older specimens) and a wing with a third, long vein sharply bent or angled forward near its tip. They may move sluggishly when indoors.

4) Multicolored Asian lady beetles (Harmonia axyridis). About 1/4- to 3/4-inch long, their color and number of dark spots varies, their pronotum (area behind head) is ivory with a thick black M-shaped (viewed from rear) or W-shaped (viewed from front) pattern. They exude irritating liquid if roughly handled, occasionally bite and can cause allergic reactions in some people.

5) Western conifer-seed/pine-seed bugs (Leptoglossus spp.). About 1/2- to 3/4-inch long, their long hind legs have a flattened leaf-like structure with a whitish zigzag band across center of their back. They are a nuisance pest.

When does the invasion start? These types of pests invade in the fall when they gather in numbers on the outside of structures. They enter buildings and homes to spend the winter so as to avoid harsh outdoor conditions.

Periodically, during the winter when outdoor conditions briefly warm, they can quickly become more active inside for a short time. Then again in the spring, as the temperature warms to above 60°F, they will temporarily cluster on the outside of the structure during the day and then come back in for the night. Typically, sometime from March to May, once the temperature stays above about 50°F at night, they will begin to leave the structure, their progeny only to return the next fall.

Where do they invade? They’re attracted to warm walls (typically the south-facing wall and the southern portion of the west-facing wall, and sometimes the southern portion of the east-facing wall). The portions of the west and east walls involved depend on how the structure is oriented. They typically land near horizontal shadows and crawl upwards looking for an entrance. Inside, they are attracted to artificial lights and windows.

Do they multiply once inside? No. They are merely seeking shelter from winter’s cold temperatures. They don’t mate and lay eggs until after they leave their overwintering site in the spring.

Preventive steps to take. Control should consist of a good IPM program. Before these pests enter their customers’ structures, pest management professionals need to make sure good exclusion techniques are employed. Seal all holes in exterior walls larger than 1/16-inch for flies and lady beetles, or 1/8-inch for bugs, (check door and window frames, check door sweeps, be sure doors and windows are tight-fitting, etc.). This is best done during May through July, with a follow-up in September. Your job is to make a detailed inspection and then to advise on the steps that should be taken.

Since these pests are attracted to lights, change exterior lighting to less-attractive yellow bulbs or sodium vapor lamps. It may be appropriate to recommend the application of a microencapsulated or wettable powder formulation of a repellent pyrethroid insecticide to help discourage pest entry for those structures with difficult or impossible to seal exteriors. The application should be made in mid-August (northern areas) to early September (more southern areas).

After the invasion has started? After they’ve invaded, it’s best to isolate the affected room(s) by sealing the insects out. Such rooms are usually located on the warm side of the structure. Typical entry points include areas around door and window frames, electrical outlets, light switches, exhaust fans, skylights and ceiling light fixtures. Because of the eventual problem caused by carpet beetles coming to feed on the dead insects, it is not advisable to kill them in walls with pesticide. They can most effectively be harvested with electrocuter-type insect light traps. However, glueboard-type ILTs should be used for the
brown mar-morated stinkbugs since electrocution often causes them to release their pungent odor. This means checking and changing the glueboard often.

If insects enter a room, they can be removed with a vacuum. Stinkbugs, however, are an exception. After a few travel down the vacuum hose, their smell can be quite noticeable and the hose will probably have to be replaced periodically. If the size of the invasion warrants, a ULV treatment can be made when the affected room is vacant. A couple of hours later, the bugs can be swept up with a broom and disposed of in a sealed plastic bag in an outside trash can.

Eric Smith is director of technical services/staff entomologist, Dodson Bros., Lynchburg, Va. He earned his undergraduate degree from Miami (Ohio) University in botany and his master’s (Purdue) and doctorate (Ohio State) degrees in entomology. He has 30+ years experience in pest management, is past president and member of Pi Chi Omega, chair of the Copesan Technical Committee, a B.C.E. and senior author of the NPMA Field Guide to Structural Pests. E-mail him at esmith@giemedia.com.

Copesan is an alliance of pest management companies with locations throughout North America. To learn more, visit www.copesan.com.