07.06.2012  
 

Oregon Winegrowers Raise Stink About Bug

Invasive pest detected in Willamette Valley towns, not yet in vineyards

 
by Peter Mitham
 
brown marmorated stink bug
 
Recent sampling detected brown marmorated stink bug at sites throughout Oregon's Willamette Valley.
Corvallis, Ore.—Vineyard watchers fear this could be the year the voracious brown marmorated stink bug (BMSB) enters local vineyards and orchards, potentially causing significant economic damage to the state’s grape crop.

Since first being detected in the state in 2004, the bug—by now well established on the East Coast and in 27 states nationwide—has been limited to urban areas. But sampling conducted in 2011 by postdoctoral researcher Nik Wiman discovered the bug in Portland, Ore., and it’s also been detected at sites in communities throughout the Willamette Valley, including Tualatin, Lafayette, Monmouth and Corvallis.

Recently a population was detected near the Hood River train station in the Columbia Gorge AVA.

 

    The danger of brown marmorated stink bug
     

     
    Brown marmorated stink bug was first documented in the United States in 1998. Originally from Asia, it has no natural predators in the U.S. and is now known to be present in 27 states nationwide.

    Peter Shearer, entomologist and director of Oregon State University’s Mid-Columbia Agricultural Research and Extension Center in Hood River, said the bug is a threat to Oregon winegrowers for several reasons:

    • It can damage the fruit by its feeding on grape berries and other plant parts and introduction of pathogens to the cluster;

    • It may reduce yields;

    • It may taint juice and wine;

    • Sprays applied to combat the bug can disrupt existing integrated pest management (IPM) programs;

    • Large numbers entering wineries and tasting rooms in the fall are unpleasant and may drive customers away.

    Key hosts for the bug in Oregon seem to be English Holly (Ilex aquifolium), Tree of Heaven (Ailanthus altissima) and, to a lesser degree, Empress Tree (Paulownia tomentosa), a common host on the East Coast.
    P.M.

“I think that all vineyard owners are concerned (low level), but since it is not showing itself as a clear and present danger, there is little being done,” said Mike Eastwick, owner of Lamonti Vineyards opposite Hood River near Underwood, Wash., and manager of two other vineyards.

“My personal concern has been raised from low to medium,” Eastwick told Wines & Vines, adding, “The area here is basically in the wait-and-see mode.”

Does the stink survive fermentation?
While the bug is reported to have destroyed more than half the Pennsylvania peach crop in 2010, little is known about its appetite for winegrapes.

Doug Pfeiffer, a professor in the entomology department at Virginia Polytechnic Institute and State University said some winemakers threw out whole batches of juice in 2010 because of a noticeable taint. “They considered it ruined,” he said.

But more recent research by Joe Fiola at the University of Maryland suggests that taint from the new stink bug may not, in fact, be permanent. Unlike the taint from Asian ladybeetles, which were an acute problem for many eastern growers during the 2001 vintage, whatever compound the new stink bugs contribute may not survive fermentation.

“There was a distinct taint in the raw juice, which is what growers were finding,” Pfeiffer said of Fiola’s trials. “However, after the fermentation and bottling process it was no longer detectable.”

The extent of damage to the grapes themselves is also unclear. The bug can cause necrosis in berries, and small wounds may lead to bunch rot and other infections, but measuring damage to date has been difficult.

Pfeiffer conceded that it’s been harder to determine the impact than in the tree fruit sector.

“Right now, we don’t really have the same economic estimate as the tree fruit growers do. Part of it may have been undetected,” he said. “The fruit is smaller, and it’s buried in with the rest of the cluster.”

Trying to answer that question is one of the goals Pfeiffer and researchers at Oregon State University are pursuing.

“We hope that it won’t become an economic issue here,” said Vaughan Walton, an entomologist and associate professor with Oregon State’s Department of Horticulture in Corvallis.

Test infestation in Pinot Noir
This spring saw a test plot of Pinot Noir vines in the Willamette Valley outfitted with exclusion bags and infested with male stink bugs (to prevent egg-laying), to study feeding habits through the season. The study, funded by the Oregon Wine Board, was designed to gauge the potential impact the pest could have on winegrapes.

“We’re letting them feed on developing tissues, canes, leaves and clusters,” Walton said. “We’ll be able to determine which parts of the plant they prefer, whether they can complete their lifecycle on vines and what the effects of the feeding would be on the clusters.”

Pfeiffer and others on the East Coast are conducting similar trials, as well as researching potential parasitoids of the stink bug’s eggs.

One potential parasitoid of the pest’s eggs, Trissolcus halyomorphae, has been identified as particularly effective and is being kept in quarantine at Oregon Sta te pending an assessment of its impact on the brown marmorated stink bug as well as local insect populations. The research is funded with a $100,000 grant from the USDA.

“That parasitoid is really very, very effective against BMSB, so the long-term strategy is get it released as quick as we can so it can start parasitizing the egg clusters of the bugs here,” Walton said. “We can, hopefully, avoid the situation that we have on the East Coast.”

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