Good Fruit Grower / October 2010 / Growers tackle ­onerous stinkbug

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Growers tackle ­onerous stinkbug

Both nymphs and adults of the brown marmorated stinkbug feed on fruit, making this a more serious threat than other species that only attack fruit in the adult stage.

Peach and apple growers in the Mid-Atlantic states are in the midst of dealing with a serious new insect pest called the brown marmorated stinkbug.   

For right now, that means they’re applying more sprays more often and, in particular, using pyrethroid insecticides, and they don’t have other good options, according to Dr. Tracy Leskey, an entomologist with the Appalachian Tree Fruit Research Station in Kearneysville, West Virginia.

She is one of the principal investigators in a newly formed research group that has applied for USDA research funding to investigate this insect, which has emerged quite suddenly as a fruit-damaging pest.

In addition, this new stinkbug, besides attacking fruit, is a major nuisance to homeowners and business operators, she said. Leskey said she herself found “literally thousands in my attic.”  They aggregate in masses, like box elder bugs and ladybird beetles, but people who decide to ­vacuum them up are met with odors far more intense than those produced by native stinkbugs, she said.
“I’ve never seen anything like this,” she said.

There are many native stinkbugs, and some of them are fruit feeders, Leskey said, but this Asian import has at least one unusual feature. With native stinkbugs, the nymphs usually feed on other host plants, like weeds, and the adults principally cause the fruit injury. With the brown marmorated stinkbug, nymphs also feed on fruit, increasing the impact of this pest throughout the season. Nymphs move through five instars on their way to adulthood.

These insects also are becoming a problem for growers practicing integrated pest management, she said.  In recent years, growers have been shifting away from organophosphate insecticides and instead applying materials more specifically targeting lepidopteran species like codling moth and oriental fruit moth.  However, with the introduction of brown marmorated stinkbug, growers are being forced to include applications aimed at controlling this invasive pest, particularly multiple pyrethroid applications, which are very disruptive to natural enemy populations.

Apparently, this new bug was accidently introduced into Pennsylvania around 1996 to 1998. Leskey said she first saw them in 2003 in Maryland, when there were just a few. Then, in 2008, growers in Maryland and West Virginia saw some damage. They saw more in 2009, and this year they have had a major fight on their hands in both peach and apple.

Damage may have occurred earlier than 2008 as well, but was masked or attributed to native stinkbugs, she said.

One member of the research team, Dr. Kim Hoelmer, also of USDA-ARS in Newark, Delaware, has headed to Asia to look for natural enemies, for there are apparently none here. Birds don’t seem to care much for the stinkbugs, either, Leskey said.

 “There’s nothing holding them back,” she said. “We don’t know where the ceiling is in terms of the population size this region can support.”
Leskey has worked with attract-and-kill methods against plum curculio. Like that insect, this stinkbug aggregates, and there is a powerful attractant that may be useful in trapping and monitoring the insect—and maybe even incorporated into an attract-and-kill strategy. Right now, she said, it’s too early to tell.

There may be lots of support for an attract-and-kill program because of the effect on ordinary people. “This is an incredible nuisance pest,” she said. “It is a large insect, and persistent in its efforts to enter homes and buildings. They aggregate en masse, and nobody wants to find 30 of them in their dresser drawer.” They seek shelter to overwinter in houses and other protected places.

Dr. George Hamilton, entomologist at Rutgers University in New Jersey, is focusing on the nuisance aspects of the bug. Other co-­investigators will work with field crops and vegetables.

Fruit industry researchers in West Virginia, Virginia, Maryland, and Pennsylvania are doing a damage survey now and also exploring methods of monitoring and managing the pest.

It is not known now how far the insect has spread, or will spread, but it is “polyphagous”—meaning it has a long list of host plants including weeds, field crops, fruit crops, and ornamental trees and bushes.

Feeding damage on leaves and fruit surface appears as small necrotic areas and ­cat-facing. 

Peter Jentsch, an entomologist with Cornell University working in the Hudson Valley Laboratory, said that stinkbug feeding injury on stone fruits produces cat-facing injury. Leskey noted that internal injury attributed to brown marmorated stinkbug feeding has been showing up in the mid-Atlantic; it appears as corky areas sometimes filled with gum. In apples, injury resembles  a bitter pit-like, shallow, circular, light-brown, corky or spongy depression with a small puncture near the center.

More information and pictures can be seen in a regional pest alert fact sheet on the Web site http://northeastipm.org. •