During the past week or two, many distraught homeowners have called regarding disagreeable shield-shaped insects congregating on doors, windows, and siding. Worse yet, in several homes these petulant bugs invaded homes and gathered en masse near windows and along baseboards. These bugs of October are brown marmorated stink bugs and members of a large clan that include the harlequin bug and green stink bug both of which are important pests of vegetables. The brown marmorated stink bug is a native of China, Korea, Taiwan, and Japan. Since its discovery in the United States in 1996 near Allentown, PA, it has appeared in most counties in Pennsylvania and in neighboring states of New Jersey, West Virginia, Delaware, and Maryland. A second wave of colonists has been discovered in Oregon and California. The extent to which this pest has colonized North America remains a mystery. In Asia it is a serious pest of fruit trees including peaches, apples, cherries, figs, mulberries, and persimmons. More disturbing than its fondness for fruit, is its appetite for soybeans. In North America this stinker has been found attacking more than seventy species of plants including herbaceous annuals and perennials and many species of woody trees and shrubs. The business end of the brown marmorated stink bug is an elongated proboscis used for sucking. Stink bugs insert needle-like mouthparts into leaves and fruit, inject digestive enzymes into the plant tissue, and slurp liquefied food into their belly.
The life history of this pest is similar to relatives we met in previous episodes of Bug of the Week such as boxelder bug, squash bug, and golden rain tree bug. After consuming a vegan diet of plant fluids all summer, the cool weather of fall triggers an instinct to find protected locations to survive winter. Before the time of man and his dwellings, refuge would be found beneath logs, vegetation, or rocky crags. However, homes and structures make nifty refuges for these opportunistic creatures and in autumn they move in. In chilly attics, foundations, and beneath sidings, stink bugs rest and wait. On warm days in March or April, stink bugs become active and may be found wandering about windows and floors as they attempt to move outdoors to find food. From June until August the mottled gray-brown females lay green, barrel-shaped eggs in clusters of 20-30 on the undersides of leaves. Young nymphs that hatch from the eggs sport black patches and lines against a background of yellow-orange. These magnificent nymphs are gregarious and often found in large numbers. Older nymphs are gray-brown with alternating light and dark bands on their abdomen, legs, and antennae. These alternating bands of dark and light on antennae, legs, and abdomen are diagnostic for this pest and give them a marbled appearance. When disturbed by a predator or a broom, they live up to their name and emit a memorable foul odor from their stink glands.
What can be done to control this invader? Officials around the nation work to delimit the distribution of this pest. If you suspect that you have an infestation of brown marmorated stink bug indoors or out, contact your State Department of Agriculture or Cooperative Extension Service. Ultimately, you will prevent these from becoming a nuisance in your household much the same way you prevent invasions by camel crickets or Asian multicolored lady bird beetle. Eliminate points of entry around your foundation, windows, facer boards, and eves by screening, caulking, and repair. If the little devils are already in your home, sweep or vacuum them, and send them to the great beyond in an environmentally appropriate and satisfying way.
For more information on the brown marmorated stink bug, please visit the following websites: