[Seasonal Invaders] Tis the Season

Features - Occasional Invaders

Impending cold temperatures, food availability and species-specific characteristics often encourage some

October 21, 2010
Dr. Mohammed El Damir

sually seasonal invaders, such as the boxelder bug, the cluster fly, the multicolored Asian lady beetle (MALB), etc., can be a nuisance by their presence. But they also will stain walls and other surfaces when handled or crushed or via their excrements or secretions (i.e., MALB secrete a foul-smelling yellowish liquid when disturbed).

Other seasonal insects produce annoying buzzing sounds when flying (i.e., western conifer seed bug, MALB, etc.). Additionally, it has been documented that the MALB can cause allergic reactions in some people. Dead insect bodies of seasonal invaders inside wall voids, cracks, and crevices attract dermestid beetles (hide beetles, larder beetles, carpet beetles, etc.) and ants (carpenter ants, etc). Both non-chemical and chemical methods can be used to control such pests. Here are some tips.

Non-Chemical Methods. Vacuum adults as they appear in buildings (do not crush them). Install insect light traps in potential overwintering sites indoors to help reduce the population and monitor the infestations. ILTs, when operated at night, are very effective. Install sticky traps indoors in common swarming areas and near potential entry points. In the summer and before late fall or early winter, seal or caulk crack, crevices, voids and all possible entry openings in and around building. Screen windows and doors, ventilators and louvers.

Chemical Management Methods. Timing a pesticide application is key to a successful seasonal pest management plan. PMPs should treat all possible entry sites of the foundation and exterior parts of structures before these pests enter. During treatment, pay particular attention to the sunny sides of the building (south and west), where these pests congregate. Treat all areas of exterior walls, especially under eaves, overhangs, under siding, around windows and doors, and all cracks and crevices of foundation and all possible entry sites. Usually an indoor treatment is not required. However, it can be done when the pests have already entered the structure in large numbers. In this situation, treat all cracks, crevices, wall voids along with spot applications to all hiding and congregating areas. Treat attics, crawlspaces, empty roof spaces, vent openings and ceilings. Remove outlet plates and carefully dust the voids behind them.

The author is technical and training director for Adam’s Pest Control, Minneapolis, Minn. E-mail him at meldamir@giemedia.com.


Boxelder Bug (Leptocoris trivittatus)

  • Adults are about ½ inch long.
  • Black with three red stripes on the pronotum.
  • The primary host plant of the boxelder bug is the female (seed-bearing) boxelder tree where boxelder bugs feed by sucking plant juices from leaves, twigs and seeds.
  • Boxelder bugs also have been observed on male boxelder, ash, maple and occasionally on strawberries, grasses and various other plants, but they usually are incapable of full development on these hosts.
  • From mid-July through mid-September, they congregate on the trunk of female boxelder trees and on the ground near these trees.
  • From mid-September to mid-October, they migrate to homes for overwintering. Only fully grown adults overwinter; immature stages die by the onset of harsh weather.
  • They first congregate on the sunny sides of the building (west, south), and then they hide deep in wall/ceiling voids, cracks, crevices and other protected areas throughout the winter.

Photo by Dr. Mohammed El Damir


Cluster Fly (Pollenia rudis)

  • About ¼ to 3⁄8 inch in length, dark gray in color with uneven light and dark gray areas on the abdomen.
  • Golden yellow hairs on the thorax.
  • Larvae develop inside an earthworm’s body.
  • The life cycle is complete in 27 to 39 days, depending on the temperature. There are about four generations per summer.
  • From late August to early September adults migrate for over-wintering in protected areas, especially the southern and western sides of a structure.

Photo by Whitney Cranshaw, Colorado State University


Multicolored Asian Lady Beetle (Harmonia axyridis)

  • About 1⁄3-inch long.
  • Multiple colors with up to 19 black spots (or no spots at all).
  • "W-" or "M"-shaped mark on thorax.
  • They can pinch the skin and cause minor and short-lived discomfort.
  • In the United States, adult beetles invade structures between late September and late October for overwintering.
  • They may bunch together in corners of porches, attics, wall voids, door or window frames or other in protected areas.
  • In the U.S., there are two generations per year. Healthy multicolored Asian lady beetles can live up to three years.

Photo by Scott Bauer, USDA Agricultural Research Service


Western Conifer Seed Bug (Leptoglossus occidentalis)

  • About ¾ inch long.
  • Brown colored insect.
  • Adults have an inverted white "V" mark towards the front of each wing.
  • Large hind legs with a flattened, leaf-like area.
  • Feed mainly on conifer seeds.
  • Entering buildings at the beginning of cold weather in the late summer or early fall for overwintering.
  • Produce a strong odor when handled.
  • Make a buzzing sound when flying.

Photo by Gyorgy Csoka, Hungary Forest Research Institute


Brown Marmorated Stink Bug (Halyomorpha halys)

  • About ½ inch long.
  • Dark mottled brown color.
  • The last two antennal segments and the exposed abdominal edges have alternating light and dark bands.
  • Adults overwinter in houses and other protected places.
  • When disturbed, the bugs produce a foul odor.

Photo by David R. Lance, USDA APHIS PPQ


Clover mites (Bryobia praetiosa)

  • About 1⁄30 inch long.
  • Oval, reddish-brown to olive to pale orange (or sometimes green-brown after feeding).
  • Have a very long pair of front legs that extend forward at the head.
  • Feed and live in clovers, grasses, trees, shrubs, lawns and other plants around buildings.
  • Clover mites are considered cool-season mites. Eggs do not hatch below 40°F or above 86°F. Eggs enter a dormant stage during the hot summer, and hatch in early autumn when temperatures fall below 85°F. Adults live one to seven months and most active between 50°F and 75°F.
  • They infest homes from November through June to overwinter. Most mites overwinter as eggs, but all life stages can be present.

Photo by Rayanne Lehman, Pennsylvania Department of Agriculture