09.09.2010  
 

Eastern Vineyards Confront New Pest

Brown marmorated stink bugs eat and contaminate fruit; scientists call for research

 
by Linda Jones McKee
 
brown marmorated stink bug
 
The brown marmorated stink bug will feed on tree fruits, small fruits, vegetables and native plants. Photo Courtesy of: The Bugwood Network at the University of Georgia and the USDA APHIS Plant Protection and Quarantine program.
 
Thurmont, Md. -- First it was the multi-colored Asian lady beetle (MALB) invading Eastern vineyards and imparting a nasty flavor to the wines. Now it’s a stink bug from China. The East has always had several kinds of native stink bugs that have co-existed with orchards and vineyards without causing any major problems, mostly because these half-inch long, shield-shaped insects did not seem to feed on fruit.

In 1996, however, an invasive species, the brown marmorated stink bug (BMSB), was first found in Allentown, Pa. (“Marmorated” refers to its marbled or speckled shell.) The numbers of BMSB gradually increased, and in the past two to three years have become a greater problem for orchards and many other crops in Pennsylvania, Maryland and West Virginia. There is concern that they are expanding their territory into Virginia as well.

The BMSB is not a picky eater. It will feed on tree fruits, small fruits, vegetables including corn, soybeans, cotton, native plants—and grapes. Both the nymph stage and the adults feed on these crops, and weather conditions in the East this summer have permitted as many as three generations of stink bugs to propagate.

Because of the extensive damage caused by the stink bugs in Maryland orchards, administrators and researchers from USDA and its Animal and Plant Health Inspection Service as well as growers and extension agents met at Catoctin Mountain Orchard in Thurmont, Md., on Sept. 3. The group visited several peach orchards to look at the scope of the problem first hand.

Dr. Joe Fiola, extension specialist in viticulture and small fruit at the Western Maryland Research and Education Center in Keedysville, attended the meeting. Fiola told Wines & Vines that at the Gardenhour Orchard in Smithburg, “50% of the crop was dropped as the fruit was picked and the ground was literally covered with peaches. Then 25%-50% of the harvested fruit was rejected after it was picked. Growers in parts of Maryland are experiencing major losses, and I don’t know how they are coping with it.”

Controlling the BMSB is a new problem for vineyard integrated pest management, and little research-based data for extension agents or growers is available. Dr. Doug Pfeiffer, a fruit entomologist at Virginia Tech, has noted that pyrethrins might be one possibility for grapegrowers to try, but that option has not been researched with stink bugs. Pyrethroids, synthetic compounds that are similar in both structure and mode of action to the pyrethrins, are another alternative, although Pfeiffer cautioned that pyrethroids may also flare other secondary pests.

The additional concern for grapegrowers is that not only do these stink bugs cause feeding injury on ripe grapes, but they also live in the grape clusters, with the possibility that they therefore could be transported to the winery during harvest. Crushing the BMSB with the grapes may lead to off-flavors, which are sometimes described as “citrusy” or “piney.” In addition, the frass (waste) produced by BMSB has been found to create a bad taste in other crops such as caneberries.

Unlike the situation with the MALB, little is known about how many stink bugs it actually takes to make a wine smell and/or taste bad. That is about to change: Fiola is planning to begin research next week in conjunction with Dr. Tony Wolf at Virginia Tech to determine the level and type of problem caused by stink bugs.

“We plan to do a controlled inoculation of juice, and add in specified numbers of bugs to different lots. Then we’ll see what happens and when,” Fiola commented. “Of course, determining the impact of the stink bugs on wine will have to wait until the juice goes through fermentation and becomes finished wine.”

Meanwhile, growers who hand-harvest their grapes can resort to sorting tables and literally pick the stink bugs out of the fruit. Other wineries with larger acreage are trying different techniques with managing their mechanical harvesters. It was reported that one winery in Maryland was attempting to slow down their harvester and blow off the stink bugs. Did that work? The answer: somewhat, but when there’s 45 acres to harvest, the grower doesn’t have many alternatives.

Obviously, a lot of work remains to be done to address the stink bug problem, and the need for answers is escalating. Wolf summed up the problem in a recent e-mail: “The magnitude of this problem is beyond the scope of any one lab or agency to manage. It will likely require a multidisciplinary, multi-state and multi-agency approach that will involve land-grant universities, the public sector and state and federal agencies.”
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