Stinky Invaders

Spring 2005


This is one bug that knows how to get your attention. It is noisy in flight, relatively large, conspicuously colored, and releases a pungent odor when handled. If you have a home in an area with coniferous trees, at one time or another you have probably had a run-in with this creature.

People commonly refer to this insect as a “stink bug.” Although it does have an odor, “stink bug” is not its true name. Its technical name is Western Conifer Seed Bug (Leptoglossus occidentalis) and it belongs to the family Coreidae, which is one of two insect families that have the ability to release a strong odor as a defense mechanism. (Pentatomidae is the other family, which are the medium to large shield-shaped bugs that are referred to as “true” stink bugs.) By the way, as a member of the order Hemiptera (true bugs), it is proper to call this insect a bug!

Western Conifer Seed Bugs are pesky because their life cycle dictates that they overwinter as adults. Hence, when they fly in the fall, looking for a sheltered place to spend the winter, they often find their way into our homes. If they successfully overwinter in or near a dwelling, they will often reappear again in the spring. (Perhaps you have more company than you realize while reading this article!)
Although obnoxious, they cause no real damage to the home (unless your entomophobic tendencies cause an overreaction and, while desperately trying to remove or escape from the bugs, you hurt yourself and/or cause unintentional property damage). The real harm from Western Conifer Seed Bugs occurs before they enter your habitat. Pines, Douglas-fir and grand fir are their primary hosts. From the time they hatch (eggs are laid on tree needles in the spring), through the various nymphal stages and into adulthood, they are either feeding on cones or on the developing male flowers of host trees.

Western Conifer Seed Bugs have no known adverse effect on the overall health and vigor of their host trees; however, they can significantly impact seed production. The damage they cause is hard to recognize because usually the cone continues to develop as if nothing was wrong, yet the entire seed contents have been removed. Likewise, it is difficult to ascertain the impact this seed loss has on the forest. However, if damage occurs in a seed orchard, especially one having genetically improved trees such as blister rust resistant western white pine, their impact can be substantial.

Currently, there are no control measures specifically targeting Western Conifer Seed Bugs. Research in British Columbia has isolated a pheromone that serves as an attractant for the bug.

Entomologists hope, that by using this pheromone, they can develop traps that target Western Conifer Seed Bugs.
Although work is being done to find ways to control Western Conifer Seed Bugs, for the foreseeable future, tolerating these “stinky invaders” is just another small price we must pay for the privilege of living among trees.

(A special thanks to Ladd Livingston, Forest Entomologist for the Idaho Department of Lands, for his help in providing information on the Western Conifer Seed Bug.)

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