Digging it Up
Stinkbug damage to a pear Submitted photo

Winter is usually a quiet time for horticulture questions at the Extension office, but one topic still has Cumberland County residents calling in - stinkbugs. Specifically, the brown marmorated stink bugs (or BMSB for short) that have taken up residence in their homes for the winter. What's to be done about them?

Unfortunately, not much at the moment; there is no easy cure. During the winter months, the stinkbugs enter a sort of hibernation called diapause when they do not feed or reproduce, but they may become more active on days when bright sunshine and warmer temperatures heat up a windowsill or a room. You may find some buzzing in sunny windows and others hiding in places such as clothing or furniture, behind pictures, in wall voids or cracks, and attics.

You can sweep or vacuum them up and throw them outside; or you can flick them into a container filled with soapy water to drown them. Try not to squash them, as this will cause BMSB to release their characteristic pungent smell, which is their defensive reaction when they feel threatened. If you do vacuum stinkbugs up, don't leave the bag in the vacuum; it will begin to smell as the stinkbugs die. Some people use a shop vac filled with soapy water to vacuum up the bugs.

This "stink" is not the same chemical as the one they release, called an aggregation pheromone, which causes large numbers of them to congregate in overwintering sites during autumn. So killing a stinkbug may cause a stink, but it won't attract more stinkbugs.

The use of insecticides, such as aerosol foggers or "bug bombs," inside the home to control BMSB is not recommended. Such insecticides are not labeled for stinkbug control, which means legally you are not allowed to use them for that purpose. And while a fogger may kill some stinkbugs, it is unlikely to reach all of those in hiding. Dead stinkbugs left in hard to reach spots, such as behind walls, may end up attracting other pest insects or animals, such as beetles or mice, which feed on the dead insects.

With the approach of spring, as the days get longer, the sunshine stronger, and the temperatures warmer, BMSB become more active as they attempt to get outside to complete their lifecycle. Once outside, the insects need to feed for about two weeks before they are able to mate and the female can lay eggs.

One female can lay up to 400 eggs before she dies. The eggs hatch in about a week, and the stinkbug goes through five nymphal stages before the final molt into an adult. Adults and nymphs feed on hundreds of different plants, ornamentals as well as vegetable, forage, and fruit crops, from spring into fall.

In the years since they were first accidentally introduced into the United States from Asia, and first detected in the Allentown area in 1998, BMSB have been considered primarily a "nuisance" pest due to their overwintering habits inside buildings. They do not cause harm to humans, animals, or pets; they are plant feeders, and do not bite, sting or transmit disease in humans. And prior to 2010, their plant feeding damage was scattered - not considered significant enough to warrant much attention from researchers or governmental authorities. They were just a nuisance.

But that changed in 2010: BMSB caused major damage to agricultural crops, and they are still spreading. They are now found in at least 29 states, up and down the Eastern seaboard, as well as western states such as Iowa, Oregon, Washington, and now in California. In 2010, many orchard growers in southern Pennsylvania, northern Maryland, and West Virginia reported BMSB damage to their peaches, apples, and pears, and some suffered losses of up to 60%.

Other crops damaged by BMSB included grapes, raspberries, sweet corn, tomatoes, peppers, cucumbers, eggplants, and soybeans. On fruit, BMSB suck out plant juices, leaving mealy, dry, brown sunken spots and distorted dimpling. Nursery and greenhouse growers also observed BMSB damage on foliage, flowers, and branches of a wide variety of ornamental plants such as crabapple, zelkova, lilac, maple, butterfly bush, redbud, dahlia, chrysanthemum, zinnia, and sunflower.

This growing threat to agriculture means that more research funding will be steered toward finding effective management strategies for BMSB; currently, no such strategies exist. The USDA's Agricultural Research Service, working with universities such as Penn State, Virginia Tech, Rutgers, and the University of Maryland, has developed a BMSB action plan, with research directed towards determining basic biology and behavior characteristics, developing monitoring tools, and finding effective management methods for both agricultural and urban settings.

This research won't happen overnight; in fact, it will take years to reach medium and long term goals for sustainable control strategies, but at least now there is hope on the horizon in the battle against BMSB.

Annette MaCoy is the consumer horticulture extension educator and master gardener coordinator for Penn State Cooperative Extension in Cumberland County. If you have garden questions, contact Annette at 240-6500 or by e-mail at ahm11@psu.edu.


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