Fruit Pest Getting Established in California
Brown marmorated stink bug, a threat to wine grapes and other crops, infests Sacramento
Sacramento, Calif.—Although the non-native brown marmorated stink bug, or BMSB, pest has been in California for a few years, experts are concerned by the recent discovery of a sizable population in the center of the state’s capital city.
BMSB has established itself in parts of Oregon and become a nuisance for orchard farmers and vineyard owners in Virginia, Pennsylvania and other eastern states. The bug has been found in parts of Los Angeles County and other areas of California but in small numbers and isolated areas.
‘A major infestation’
The most recent discovery, however, of a well-established population that had been present for some time in the area, could mean the pest is becoming more entrenched in California. “Oh my gosh, it’s an infestation,” said Chuck Ingels, the University of California Cooperative Extension advisor for Sacramento County. “You can walk Midtown and find them everywhere. It’s a major infestation.”
Ingels said the population was only discovered when a resident in the area mentioned the bug to a UC master gardener who in turn happened to say something to a friend who worked for the California Department of Agriculture. “We don’t know how long it’s been there, but one of the residents there said they saw them in June of this year.”
Native to Asia, the pest first appeared in the United States in Pennsylvania in 2001. BMSB eat a variety of fruit including grapes, but they have the biggest impact on orchard crops that need a clean appearance to appeal to consumers.
The pest left its biggest mark in the East in 2010, causing a reported $37 million in damage to the eastern apple crop. At the time, grapegrowers were most concerned that bugs hidden in grape clusters would get crushed into juice and eventually impart their hallmark stink to finished wine.
Research by Dr. Joseph Fiola, the extension specialist for viticulture and small fruit at the University of Maryland, however, found that finished wine made with BMSB-tainted fruit did not exhibit any malodorous qualities.
That research allayed fears from grapegrowers, but Dr. Doug Pfeiffer, an entomologist with Virginia Polytechnic Institute & State University, said the pest has been an issue for a few growers this year.
Grape damage still a concern
Pfeiffer said following the major outbreak of 2010 populations of BMSB declined in 2011 and 2012. They rebounded this year, although not to the level of 2010. The pest wasn’t an issue for most vineyards, but in some places the population was so large that crop damage was a concern.
After feeding on ripening grapes, BMSB can leave small areas of necrosis, or dead tissue on berries. This damage is of little concern if there’s no sensory impact on the finished wine, but too much damage could potentially ruin a cluster.
Pfeiffer said he and a graduate student are currently working to determine a population threshold to help growers decided when to spray for BMSB. Spraying for BMSB, however, presents its own issues.
Spraying a challenge for IPM
Chris Bergh, a professor of tree fruit and grape entomology with the Virginia Tech extension, said treating for BMSB has required orchardists to change management practices significantly using broad-spectrum insecticides such as synthetic pyrethoids that also disrupt beneficial insects, which are part of an integrated pest management program.
The United States Department of Agriculture is researching parasitoid Asian wasps that could serve as a natural control for BMSB, but the results of those tests are still a couple years off.
Ingels said there’s no way of knowing where BMSB could be discovered next in California, or when the pest could become a serious threat to California agriculture.
The best indication of what may happen in California may be found in Oregon, where researchers and growers are anxiously waiting to see how much of a problem the pest poses. ( See “Oregon Winegrowers Raise Stink About Bug.”)
The California Department of Agriculture currently is laying out traps to gain a better understanding of the state’s population of BMSB, and Ingels suggested growers in the Sacramento County area could do the same. He also referred them to the county extension’s website, where they could find more information about the pest and also report if they’ve found them on their property.