Species Facts:

Typical of other stink bugs, the Brown Marmorated Stink Bug, Halyomorpha halys, has a shield-shaped body and emits a pungent odor when disturbed. These bugs are very active and drop from plants or fly when disturbed. The best field characteristic for adults is the white band on the antennae.

Originally, populations in Pennsylvania were limited to ornamental plants, garden crops, fruit and shade trees in suburban areas and urban landscapes (Bernon et al. 2004). Damage was observed on several ornamentals, including butterfly-bush (Buddleia spp), and the princess tree (P. tomentosa). Both adults and nymphs fed on the leaves of these two host plants, and leaf damage was very apparent by the end of the season (Bernon 2004). These two ornamentals may attract the stink bug as it spreads to new areas, and homeowners are likely to be the first to see this new pest. Significant damage was also reported on urban peach and pear crops. Following the first official identification of the Brown Marmorated Stink Bug, Bernon et al. (2004) found Brown Marmorated Stink Bugs on over 60 host plants. Because the bug is polyphagous, or feeding on a wide range of host plants, almost any crop with fruit may be at risk.

Late in the season, adults will enter homes and other buildings when seeking sheltered sites to overwinter, or diapause. During the several weeks of peak flight, many insects can enter homes through any small opening, mostly around windows. In Japan, the Brown Marmorated Stink Bug is a well-known nuisance pest for this reason, and the same situation is now common in Allentown, Pennsylvania in late September and early October. This nuisance behavior resulted in many complaints to the Lehigh County (Allentown) Cooperative Extension Service, and ultimately resulted in the identification of this new invasive pest. As the insect spreads to new areas, this aggregation behavior will probably again attract attention and ironically assist in monitoring its distribution. The nuisance aspect is a major concern in suburban areas and may distract from the potential future agricultural risks (Bernon 2004).

Life Cycle and Description

Eggs: The white or pale green barrel-shaped eggs are laid in clusters on the undersides of leaves. Egg masses have about 25 eggs that are only about 1 mm in diameter but become apparent when nymphs have recently emerged, as they will stay at the egg mass for several days. In Pennsylvania, eggs first appeared in late June, but females continued to lay egg masses until September. Although only one generation was observed, there are likely to be multiple generations as in southern China. Up to five generations occur each year.

Nymphs: As with all immature stink bugs, the nymphs lack fully developed wings and have been described as tick-like in appearance. Nymphs need to molt, or shed their exoskeleton, as they progress through five different stages or nymphal instars. The Brown Marmorated Stink Bug has five nymphal instars, and each stage lasts approximately one week, depending upon temperature. First instar nymphs emerge four to five days after eggs are laid. They are orange or red in color and remain clustered around the egg mass, sometimes until they molt to the 2nd instar stage. The 2nd instar begins to develop an almost black appearance, and subsequent instars (3rd, 4th, and 5th) begin to acquire more of the adult Brown Marmorated Stink Bug coloration. These bugs range in size from 2.4 mm (1st instar) to 12 mm (5th instar). Nymphs are solitary feeders, but they occasionally aggregate between overlapping leaves or leaf folds (Bernon 2004).

Adults: Adults are 12 to17 mm long (approximately 1/2 inch), and have a mottled appearance. Alternating dark and light bands occur on the last two antennal segment. Additionally, the head and pronotum are covered with patches of coppery or bluish metallic-colored punctures and the margins of the pronotum are smooth as compared to the toothed, jagged pronotal margin of Brochymena (Hoebeke 2002). The exposed lateral margins of the abdomen are marked with alternate bands of brown and white. Faint white bands are also evident on the legs.

Laboratory studies indicate that adults are sexually mature two weeks after their final molt (Hoebeke and Carter 2003). The adults mate in the spring approximately two weeks after emerging from diapause or the resting phase. After a short period, the females begin laying egg masses. Egg masses are laid at approximately weekly intervals, and each female lays as many as 400 eggs in her lifetime. In Pennsylvania, females were observed laying eggs from June to September. Since females continue to lay new egg masses throughout the season, different nymphal stages were often observed on the same host plant.

Portions of this article courtesy of: Brown Marmorated Stink Bug
Image of a Brown Marmorated Stink Bug (Photo from: www.bugwood.org Credit to:
David R. Lance)