Where have all the stink bugs gone?

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What's bugging entomologists as summer begins? Stink bugs, but not in the way you would think.

Tim Nagy, 45, of South Fayette, was "dive-bombed" by stink bugs all over his home last year -- so bad that his dog began eating them for fun. This year, however, he has hardly seen any.

Mr. Nagy, like many Western Pennsylvanians who were distraught over the stink bug invasion of the past two years, now is asking, "Where did they go?"

Entomologists and researchers don't have a cut-and-dry answer. While stink bugs have disappeared in some Western Pennsylvania areas, they're still thriving in others.

Allegheny County Health Department entomologist Bill Todaro takes stink bug calls at his office. He said he had "hundreds in 2010, less in 2011 and maybe one or two this year."

Tracy Leskey, a research entomologist at the USDA Agricultural Research Service, has been nose-deep in stink bugs since the 2010 invasion.

She and 52 other researchers from various states formed the Brown Marmorated Stink Bug IPM Working Group, a West Virginia-based organization dedicated to monitoring and collecting data on the bug.

The group found that fewer adult stink bugs were over-wintering last fall -- invading homes to escape the cold -- and thus fewer re-emerged this spring as compared to 2010.

Researchers believe weather is the main cause. Ms. Leskey said atypical weather patterns, such as tropical storms and heat waves, disrupt the stink bug's breeding.

The brown marmorated stink bug usually hatches a single generation per year in Pennsylvania, said Penn State entomologist and group member Steve Jacobs. This keeps the population under control, but warm springs and summers can allow up to three generations in a single year.

Like in previous years, the stink bugs started laying eggs early in 2012 because of the warm spring, but the temperatures this season were not constant. Ms. Leskey said there is an optimal temperature range for breeding, and outside of that range the eggs won't develop.

So residents should be grateful for the heat wave sweeping across Pittsburgh as summer begins. The expected high temperatures lie outside the stink bug's optimal range, which could help to keep the population under control.

Ms. Leskey admits that atypical weather is only an educated guess for why stink bugs are declining in some parts of the region.

She and the research group haven't collected enough data and haven't sufficiently monitored the bugs to provide a definite answer.

Some experts also believe the bugs have migrated from Western Pennsylvania.

The highest density is still in the Mid-Atlantic, Ms. Leskey said, but states such as Ohio and Kentucky have reported problems with the bug. Celeste Welty, an extension entomologist at Ohio State University, said Columbus, Ohio, has been the "hot spot" for stink bugs for the past two years.

Down South, stink bugs have been detected in Georgia and Florida, but they haven't established themselves there, experts say.

So while the population has diminished in some parts of Western Pennsylvania, stink bugs have not completely left.

Sewickley Heights -- rated one of the worst areas of infestation by some extermination companies -- is still teeming with stink bugs. Borough manager Bill Rohe sees them around his office on a daily basis, nearly as many as in 2010.

Tim Abbey, horticulture educator for the Penn State extension service, handles Pennsylvania counties east of here -- including Lancaster, York and Cumberland -- and reported seeing only a few bugs this season. After the previous years' invasion, farmers immediately adopted practices to protect their crops, such as using pesticides, which he believes curbed the population.

He also suspects that natural predators have emerged to help level out the stink bug's presence, such as parasitic wasps and praying mantises.

As for maintaining the relatively stink-bug-free summer in Pittsburgh, Edward McCoy, owner of Stink Bug Specialist, said that "every summer, [the stink bugs] decline but then come back in the fall." His home-based business works out of three locations, in Penn Hills, North Hills and South Hills. Mr. McCoy says he is busiest between August and November.

Researchers with the Brown Marmorated Stink Bug IPM Working Group will continue to monitor population levels around the Mid-Atlantic throughout the summer. However, researchers don't have a definite answer about what to expect in the fall.

That means there's still a chance they could return in full force. All residents can do is keep their fingers crossed -- and their noses pinched.

nation - region - environment

Emily Dobler: edobler@post-gazette.com or 412-263-3873. First Published June 20, 2012 4:00 AM


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