Pests Continued from Page 6
trademarked Plinazolin technology, he said. Other researchers say improved biolog- ical control may also help strawberry and blackberry growers control spotted wing drosophila, an exotic vinegar fly from Asia that is particularly damaging to soft fruit. In the 15 years since spotted wing dro- sophila first appeared in California straw- berries, the pest has already developed resistance to widely used insecticides. The vinegar fly punctures the surface of soft fruit such as strawberries, blackberries, raspberries and ripe cherries, depositing its eggs under the surface. “There’s a lot of natural enemy activity going on right now,” said Kent Daane, a bi- ological control specialist at the University of California, Berkeley. “Unfortunately, it’s not enough to control the pest. We’re look- ing at importation and augmentation of natural enemies, and some members of our group are looking at beneficial fungi and bacteria.” In cooperation with berry producer Nuturipe Farms, researchers attempted to release large numbers of natural enemies when pest populations approached levels that posed economic damage. The experiment proved to be limited because the beneficials had to be re- leased numerous times and failed to es- tablish populations. Meanwhile, researchers have had to look
Researchers are studying new insecticides to treat the lygus bug, above, and biological controls for the spotted wing drosophila, left. Both can damage strawberries.
to Asia for the most effective beneficials. “In classic biocontrol, you go to the na- tive area of the pest—Asia—and find natu- ral enemies that will maintain a stable pop- ulation,” Daane said. “You introduce some of these into the system, and they keep the pest population down to acceptable levels.” Research in Asia uncovered 20 poten- tial biological controls. After five years, the U.S. Department of Agriculture allowed the importation of one—the parasitic wasp Ganaspis brasiliensis—because it attacks only spotted wing drosophila and closely related species. Researchers have released Ganaspis in numerous locations, including in Salinas and Santa Maria strawberry-
growing regions, but the beneficial failed to establish robust populations in berries. “We need to understand why Ganaspis is not doing as well in California as in Canada and Delaware,” Daane said. “My worry is that the hot, dry summers in California are not conducive to parasitoids. We’re going to import Ganaspis popula- tions from southern China, where there are hot summers.” Unfortunately, the most widely used materials to control spotted wing drosoph- ila are hard on this beneficial. “Malathion, Entrust and Mustang Maxx were the most toxic to Ganaspis,” Daane said. “Grandevo was the least toxic material, but it was not effective
against spotted wing drosophila.” The strategy is to release Ganaspis to knock down pest populations in areas where these insecticides are not used. “If we have success with imported bio- controls, we’re going to focus on riparian zones outside the cropping system be- cause we have movement of spotted wing drosophila from these riparian zones into the cropping system,” Daane said. “If we can lower the number of spotted wing dro- sophila coming into your strawberries and blackberries, that will make the chemicals more efficient.” (Bob Johnson is a reporter in Monterey County. He may be contacted at bjohn11135@gmail.com.)
April 17, 2024 Ag Alert 7
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