Signs of Fall 7: Stink Bugs (again)!

Photo by D. Sillman

In mid-September, 2009 I came across my first brown marmorated stinkbug (Halyomorpha halys). I found several of them up on campus, put them into a terrarium, added some grapes and some wet filter paper for moisture and then turned them over to an interested student who kept them alive all winter. We were amazed that 100% of these stink bugs survived to spring! Boy, were we ignorant! (see the Brown Marmorated Stink Bug species page out on the Virtual Nature Trail!)

Since then, every September and then again every May, population explosions of these stinkbugs have become very unwelcome signs of both spring and fall. In Fall 2012, there were such huge numbers of stinkbugs trying to find places to hibernate up on campus that they were crowding into electrical switches and circuit breaker boxes and short circuiting the heating and air conditioning systems! On one occasion the masses of stinkbugs even activated a fire alarm, and the campus’ buildings had to be evacuated!

In spring 2013 we had an extremely large outbreak of stinkbugs at my house. The hallways and rooms, porch, and deck were covered with squirming masses of them. Well into late June we captured and killed them by the thousands! We filled up dozens of plastic and glass bottles with dead and dying stinkbugs and even got house guests to join in the hunting and gathering (we throw really fun parties!).

Photo by D. Sillman

The spring 2013 explosion was the peak of stinkbugs around here, but by no means are they gone or forgotten. A few weeks ago, we accidentally left a bedroom window screen open for a few hours and then returned to find a room full of stink bugs. They all ended up in an old wine bottle that I happened to have on hand. Once I had captured all of the intruders I put the bottle out in the sun to quickly heat-kill them.

The stink bugs are looking for overwintering hideouts. Their ability to use human habitations for their hibernation is an incredibly successful adaptation both here and back in their home ecosystems. They doze away the winter, emerge and mate in the spring, and then disperse their eggs out in the surrounding vegetation and let the next generation hatch and grow and develop. Each female is able to produce many hundreds of viable eggs from a single mating! Researchers have found that these stink bugs can feed on over three hundred species of plants, so there is almost always something within the range of a growing stink bug population upon which they can feed.

Photo by D. Sillman

These stink bugs are an exotic invasive species from northeast Asia (especially Japan and China) that hitched a ride to the United States in a shipping container less than ten years ago (probably 1996). They landed in Allentown, Pennsylvania and have been explosively dispersing and increasing in numbers ever since. At first potential predators were few and far between (they are called “stinkbugs” for a very good reason and most predators are repelled by the stench they produce when they are disturbed). In Fall 2013 and again last fall, however, Deborah and I noticed that spiders and some birds (especially titmice and chickadees) were starting to actively hunt and eat stink bugs. Deborah filmed a spider wrapping up a stinkbug in its webbing (photo above), and I watched a number of chickadees fly up to the screens on my back windows in order to grab stink bugs and take them to a nearby perch to eat them. Was nature reestablishing an equilibrium? My local observations of this increased predation correlated with smaller and smaller seasonal outbreaks of stinkbugs, and the numbers here in the fall (2015) are still well below the spring 2013 peak.

These hopeful observations, though, may just be a local phenomenon. Nationwide, the stinkbug invasion is getting much worse. Dr. Michael J Raupp (College of Agriculture and Natural Resources, University of Maryland) wrote a short article entitled “The Truth About Stinkbugs.” In it he reports that stinkbugs are now found in thirty-eight states, they have moved on from primarily attacking fruit (apples, pears, and peaches) to feeding on soybeans, corn, tomatoes, peppers and many other vegetables. The economic impacts of their feeding on these food crops is huge. In 2013 18% of the mid-Atlantic region’s apple crop was destroyed for an estimated growers’ loss of $37,000,000.00! The total economic impact of the loss, though, might have to be multiplied four or five times to account for the losses through the entire supply chain of the crop!

We need to know much more about this species before we can adequately control it. Researchers all over the country are exploring the feeding behaviors, mating physiologies, and dispersal mechanisms for these insects and are trying to construct models of their habitat requirements and restrictions. An interesting observation by researchers that might help to explain the amazing resistance of these stink bugs to most pesticides concerned their mobility. Since the stink bugs feed on crops and then frequently move into non-crop habitats, the application of pesticides often occurs when they are not on the target plants!

Photo by D.Sillman

One of my students, Brady Boyer, studied the behavior of the brown marmorated stink bug a few years ago and found that were attracted to yellow surfaces, and that they preferred cool, moist places that were also well lit. Further, he found that they were strongly attracted to specific pheromone chemicals. So, if we made a damp, yellow, cool, well-lit trap and sprayed some attraction pheromones on it, we should be able to very efficiently catch large number of brown marmorated stink bugs! It would be much easier that catching them one by one in a bottle!

The brown marmorated stink bug is not just a seasonal nuisance, it is a very significant agricultural pest that is causing many millions of dollars of damage every year. It is likely that we will never be rid of it, but hopefully we and some of our fellow species in our ecosystems can come up with ways to control their numbers and their extent of damage.