Marmorated Stink Bugs - Increasing in Many States

One more stinking bug is increasing its population in many East Coast, West Coast and  Midwest states—the brown marmorated stink bug, Halyomorpha halys. This bug is another gift from China/Korea/Japan area. As if you didn’t have enough new bugs in your life, thanks to the worldwide trade and the transporting of bugs, we have one more to keep an eye on. This bug was first reported in Allentown, Pennsylvania in 2001. Since this first sighting it has invaded New Jersey, Delaware, Maryland, the District of Columbia, New York, Ohio, and Massachusetts. It has also been found in Oregon and California.

Why Are We Concerned?

Good question. It is just another true bug and we have plenty of native species of true bugs. Exotic species such as the marmorated stink bug are especially bad because we do not have  their natural enemies around to keep populations in check. The damage they cause is inflicted by its sucking mouthpart used to pierce the host plant when it feeds. Where this occurs on foliage or fruit, a small necrotic area forms. Feeding on apples and peaches causes tissue damage, resulting in distorted fruit that just does not look appealing. Unfortunately, it also feeds on plants such as raspberries and blackberries, causing fruit to abort or be misshapen.

With the current economy, many people are including fruit trees in their landscapes and will likely encounter this new pest. In New Jersey this bug is causing damage in orchards and is  reportedly feeding on ornamental plants and even vegetables. I know lots of people are planning on planting vegetable gardens this year and this bug is reported to feed on asparagus, green beans and peppers. In the ornamental landscape this bug has been found feeding on crabapples, maple, basswood, sweet gum, redbud, American holly, pyracantha, vibur-num, rose and persimmon.

It has not yet been reported on cut flowers. It has been found damaging peppers and legumes such as soybeans. We are interested whether it will damage ornamental peppers, or feed on legumes such as baptisia, both grown by cut flower growers. We would be interested to know if you detect this bug damaging any of your cut flower species this year. Please contact me (see email address below).

A Highly Mobile Bug

Since this bug was first found in Pennsylvania it has managed to spread itself across the United States very rapidly. In February of 2009 one was found hitchhiking a ride in a mobile home in Florida. It is now established there and we will see what damage it causes in this tropical area. The insect is mobile in the growing season and can easily and rapidly switch host plants. It has been reported to begin on early-spring-ripening fruit, move to foliage-feeding on other plants, and end up damaging late-season fruits, vegetables or ornamental plants.

When the brown marmorated stink bug feeds on beans it cause the seeds within the pod to malform or not form at all. On fruit crops the feeding causes small necrotic spots. If peaches or plums are damaged early in the season it causes distorted growth of the fruit called cat-facing. Fruit damaged later in the season has lesions that look like water-soaked spots on the surface. If they are crushed they have a distinct, slightly minty-foul odor that is difficult to get off your hands. The taste is awful if you handle a bug and get this flavor in your mouth. Leaf feeding is characterized by light-colored stippling or lesions. The lesions sometimes coalesce and turn brown over time.

This bug has an additional “bonus” feature—it overwinters as an adult insect, usually in people’s houses or offices. In the fall, seek shelter sites to spend the winter. The bugs are harmless to humans and will not bite people but they become a nuisance. In spring they will migrate outdoors to mate and lay eggs.

Recognizing the Insect

The brown marmorated stink bugs looks much like any other stink bug, with a typical shield shape. The size is usually about ½-5/8” long and 3/8–½” wide across the broad part of the shield. The body color is a mottled gray to brown. The distinct characteristics of marmorated stink bug that separate it from other stink bugs is the presence of  alternating light and dark banding on the exposed side of the abdomen when viewed from above.

If you look at the antennae you’ll see alternating light and dark bands on the last two segments. The eyes are dark red and the legs are brown with a light white banding. Females lay clusters of barrel-like eggs on leaf surfaces. The young nymphs are yellow to brown with black and red markings. As nymphs mature the banded antennae and legs seen in adults is evident.

A Bug’s Life (Cycle)

The brown marmorated stink bug emerges from overwintering sites such as houses and offices in April through May and feeds on developing fruit or leaves in spring. Males and females mate, and egg laying starts in May about 2 weeks after mating. Females lay eggs in clusters of 25-30. Eggs can be found from May through August, usually on the undersides of leaves. One female can lay several hundred eggs in her lifetime. The nymphs pass through 5 instars with each stage lasting 5-7 days. The summer generation adults start to show up in late July and will present through the fall in the landscape. There is one generation per year here in Maryland.

Tracking and Control

We are interested in tracking where this bug shows up in the United States and what new plants it is reported damaging. Contact a local Extension office if you think you have marmorated stink bugs. You can also report them at a Rutgers university website https://njaes Rutgers.edu/stinkbug/report.asp.

Systemic insecticides such as acephate (Orthene) or imidacloprid should provide control of feeding nymphs or adults on foliage. Evaluate whether the population is high enough to warrant treatment. Synthetic pyrethroids such as bifenthrin (Talstar) or permethrin  (Astro) should provide control of the nymphs and adults.

Stanton Gill

Extension Specialist

Stanton Gill is an extension specialist (professor-ranked principal agent) in IPM and entomology with the University of Maryland Extension, based at the Central Maryland Research and Education Center in Ellicott City. He is also a professor in the Landscape Technology Program at the Germantown Campus of Montgomery College. Contact him at [email protected]