Wild multiflora roses, once considered a nuisance in orchards, are now being planted around apple, pear and cherry orchards in Washington and Oregon in a new Integrated Pest Management strategy to combat leafrollers.
Scientists discovered that wild roses and strawberries provided overwintering sites for another type of leafroller, the strawberry leafroller, which in turn provides winter food and habitat for a tiny parasitic wasp, Colpoclypeus florus. The parasitic wasp is a powerful natural enemy of the apple leafroller, causing up to 50% mortality when it is present in orchards in summer. But the wasp is usually not present in spring, when leafrollers are most active in orchards, sometimes causing yield losses greater than 50%.
Recently, though, scientists from USDA’s Agricultural Research Service and Washington State University discovered the wasps overwintering in roses and strawberries. They reasoned that if orchards were surrounded by winter habitat for the wasps, they might be expected to emerge en masse during the spring.
Results so far suggest that making these orchards more hospitable to the parasitic wasps could ease or even eliminate the need for spraying leafrollers. “I’m convinced we can do away with most sprays,” says Tom Unruh, with ARS’s Tree Fruit and Vegetable Insects Research Unit in Wapato, Washington.
For more, see the January 2004 issue of Agricultural Research magazine at http://www.ars.usda.gov