Stink Bug Activity

Already taken firm root in several eastern states, the brown marmorated stink bug is making steady progress across the rest of the country. It has managed to spread to 39 states, Washington, D.C., and into Canada.

Here in Maryland, populations dropped a bit in 2012, but after overwintering in barns and houses, the pests are again swarming the general landscape. Several cut flower growers opened their market tents to find hundreds of BMSB hiding in the canopies. It certainly does nothing for your market debut when you open your tent and bugs rain out of it.

What concerns us is that the brown marmorated stink bug has such a broad potential host plant range. It has been observed on many diverse plant species, both woody and herbaceous, including tropical ornamentals.

Trees, shrubs, and ornamental plants near their overwintering shelters often serve as the best places to observe early indications. As adult activity increases throughout June and as mating, egg laying, and nymphal development occur throughout the summer, BMSB can be found on a  range of plant species. Cut flower growers often harvest plants with berries and pods and often the BMSB will be found feeding on these plants.

Last summer we spent time wandering about commercial cut flower growers’ fields looking for BMSB on their cut flowers. The good news is BMSB appears somewhat selective and prefer to feed on a just a couple of major cut flower species. If you are growing nandina and other berry-producing cut woody stems expect to find BMSB feeding on the fruit. Injury to edible fruit is significant, but damage to ornamental fruits may be more limited.

In 2012, Dave Dowling helped us focus on one particular plant – amaranth. He reported BMSB were all over the flowers in large numbers. We observed nymphs and adult in mid-August, with the majority feeding on the flowers. The damage was really not detectable last year but we can say that this plant is highly attractive to the nymphs and adults. This plant appears to be a good trap plant for this pest and you might consider growing it just so you will know when they are active in your local area.

The interesting thing is ‘Limelight’ hydrangeas were being grown in an adjacent planting; we found adult BMSB on its foliage, but not feeding on it. This year, there will be no amaranth near the hydrangea, so we’ll get the chance to determine whether the BMSB can be a pest on hydrangea.

This year Dave planted a row of amaranth in a new location. We’ll monitor it summer through fall to see if adults lay egg masses on the plants, and if we detect nymphs and adults feeding. We’ll also monitor sunflowers and zinnias on a weekly basis, since we observed both nymphs and adults feeding on those flowers last year.

In the case of sunflowers the BMSB were feeding on the flower head and ray petals. If the flower was left on the plant to fully open, the feeding caused a spotting of the ray petals. Since sunflowers are harvested as the petals unfold, there may not be enough time for feeding damage to become visible before the flower is sold.

Damage to zinnias was minimal, as flowers were harvested twice a week.

The most popular cut flower plant we found BMSB moving about the foliage on was dahlias. The nymphs and adults were feeding on the flower heads and some were found on the foliage, but none was observed feeding on the leaves. We’ll monitor these this year as well, to see if egg laying occurs on the plants and whether nymphs and adults are damaging this crop.

The good news is that we are finding more birds feeding on brown marmorated stink bugs, and local parasitoids are starting to adapt this invader as a food pest, including native wasps. This is reason for optimism!

Regional extension personnel are working with us to monitor BMSB in herbaceous perennial nurseries: Brian Kunkel in Delaware and Pennsylvania, Ginny Rosenkranz on Maryland’s eastern shore, and Debby Smith-Fiola in western Maryland. We’ll be busy updating all growers on the progress of this important horticultural pest.

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]