Brown Marmorated Stink Bug Threatens Biological Mite Control in Pennsylvania Apple Orchards

Online, March 8, 2011 (Newswire.com) - A Penn State biological control program that saves apple growers over $1 million in insecticide use each year is being threatened by the expected increase in pesticide use due to a new invasive pest, the brown marmorated stink bug.

Tree fruit is a $70 million a year industry in Pennsylvania, with the majority of the fruit being grown in the southern part of the state. With the help of the Pennsylvania State University Fruit Research and Extension Center, family-owned Lerew Farms, Inc. became one of the first growers in the state to move away from broad-spectrum insecticides and transition to more pest selective and environmentally safer insecticides in the mid-1990s using integrated pest management (IPM).
Pennsylvania's Integrated Pest Management Program has resulted in apple growers using fewer and safer pesticides. IPM promotes the use of safer and more environmentally compatible pest control practices.

At Lerew Farms, which has about 1,000 acres of fresh market apples and processing tart cherries, Penn State tree fruit entomologist Dr. David Biddinger discovered increasing numbers and diversity of beneficial insects in orchards. These beneficial insects significantly reduce outbreaks of secondary pests, such as mites, aphids and leafminers. According to Biddinger, most striking was the lack of outbreaks by the European red mite, a major target of pesticides in the past. "Most growers were averaging about $150 to $200 per acre in insecticide and miticide costs with about one third being spent just to control mites."

In addition, Dr. Biddinger discovered a new mite predator, Typhlodromus pyri, never before seen in Pennsylvania orchards. Effective biological mite control programs in apple using T. pyri existed in parts of New York, New England and Washington, but never in the Mid-Atlantic States despite several intensive surveys. "It was generally thought that T. pyri is a cool region predator that could not adapt to a warmer climate, but an intensive survey of other Pennsylvania fruit farms found it to be present at lower levels on a number of other farms that were using mostly selective insecticides," Biddinger said.

IPM creates an orchard environment where natural enemies of pests can survive. Unlike other mite predators, T. pyri spends its entire life on the tree so that a toxic insecticide application anytime during the season would wipe out the population. "Because T. pyri never leave the tree, it is a more effective mite predator," Biddinger explains."In addition, T. pyri has the unique ability to feed pollen and fungal spores at times when the pest mite prey were very low. Other mite predators can't do this and only move back into the orchard when pest mite populations are high and already causing significant damage."

Once T. pyri was discovered at the Lerew orchard, researchers transferred branch clippings to other orchards in the spring and fall. "Using Lerew's and the Penn State research orchards as two T. pyri 'seed sites', we quickly established the predator in the majority of Pennsylvania's 22,000 acres of apples," said Biddinger. It is estimated that this conservation biological control program is seasonally reducing miticide use in Pennsylvania apple orchards by almost a ton and saves growers over $1 million a year. Not only was controlling mites with miticides expensive for growers, but also it was non-sustainable since the pest mites developed resistance to all new products within three to five years.

The project was facilitated by financial incentives provided to the growers through USDA-Natural Resources Conservation Service (NRCS) conservation programs and through conservation guidelines provided by Penn State. T. pyri from the original Lerew Farms site have now been spread and established in Maryland, Virginia and West Virginia through similar USDA-NRCS conservation programs.

Unfortunately, the entire tree fruit IPM system is being threatened by a new pest. In 2010, brown marmorated stink bug (BMSB) moved into the mid-Atlantic fruit-growing region and did extensive damage to apple and peach crops. Some growers lost 40 percent or more of their crop. Researchers know very little about managing BSMB since this insect is a recent arrival from China and has just begun to severely affect agriculture. According to Biddinger, fruit growers are faced with a terrible choice: extensively and frequently spraying with broad spectrum insecticides to ensure control of BSMB, or not extensively spraying to preserve the IPM system, but risking yield losses and lower profits from BSMB damage. "In either case the cost of production will rise or the supply of apples will decline maybe resulting in higher prices for the consumer."

Research programs investigating safer and cheaper ways to control BSMB are starting, but scientists have much to learn. "In the meantime, fruit growers will do the best they can to manage pests in a safe way, while hopefully not going out of business," says Biddinger.

Current PSU recommendations for establishing and conserving biological mite control with T. pyri are annually updated at: http://extension.psu.edu/ipm/resources/nrcs/programs/conventreefruit/biocontrolmites/view and a more complete report on the discovery and development of T. pyri in Pennsylvania can be found at: http://extension.psu.edu/ipm/resources/nrcs/presentations/mite-control/view. For more information on tree fruit IPM, contact Dr. David Biddinger at (717) 677-6116 or by e-mail at djb134@psu.edu.