USDA AGRICULTURAL RESEARCH SERVICE
Information Staff, 800 Buchanan St., Albany CA 94710
Dennis Senft, (510) 559-6068 or (301) 344-2303
firstname.lastname@example.org OR CIS 75703,2704
Mediterranean Insects Brought Here to Control Field Bindweed
PROSSER, Wash., July 12--Having proved they could live through last winter's sub-zero temperatures, tiny Mediterranean mites are again being unleashed by U.S. Department of Agriculture researchers to attack field bindweed.
Bindweed infests millions of acres of wheat, corn and other crops, particularly in the Pacific Northwest, said Rick A. Boydston, a plant physiologist with USDA's Agricultural Research Service. He and colleagues at ARS' Irrigated Agriculture Research and Extension Center in Prosser want to know if the imported leaf-eating mite Aceria malherbae can eventually help rein in the weed, one of the world's 10 worst.
The mites feed on bindweed leaves, causing galls to form on leaf surfaces. These galls are abnormal swellings of tissue which usually don't kill the weed but can sap its strength and keep it from growing or reproducing.
This gall does double duty. It not only injures the bindweed, but protects the helpful mites from herbicides. "The mites just keep feeding on the weeds, so a two-pronged attack is possible," said Boydston. His preliminary tests show that using the mites along with safe, registered herbicides works better than using either the insects or herbicides alone.
"In fact, the mites appear to make the bindweed more susceptible to some herbicides. This could allow reduced herbicide applications while getting good weed control," said Boydston.
"We released test mites last August and September near Prosser so they could burrow into weed roots before winter hit," said Boydston. "They survived despite several days of sub-zero temperatures in January." He said that was the first report of a gall-forming mite overwintering in Washington.
To boost the mite's population, Boydston released in late June about 10,000 at the Prosser research station and in a research vineyard owned by Stimson Lane Winery near Grandview, Wash. The Mint Industry Research Council and Benton County Noxious Weed District are cooperators in the release.
Boydston said field bindweed (Convovulus arvensis) "is a particularly troublesome perennial weed that competes with crops for water and nutrients on millions of acres of wheat and corn in the United States." Crop losses and control costs in only two Washington counties--Yakima and Benton--exceed an estimated $5 million annually.
Called bindweed because it wraps itself around plants, sometimes completely enveloping them, the plant can send its roots 20 to 30 feet deep. Control is especially hard in vineyards, tree fruit and mint crops.
Boydston got the mites from ARS entomologist Paul E. Boldt, based at ARS' Grassland, Soil and Water Research Laboratory in Temple, Texas. ARS scientists located in Europe collected and supplied the mites to Boldt in Temple a few years ago.
Boldt has reared them for releases in Texas, Montana, Kansas and New Jersey to combat bindweed.
Another promising European agent for biological control of bindweed is waiting in the wings in Boldt's lab. Caterpillars of a Mediterranean moth--Tyta luctuosa--also eat bindweed leaves.
"Field bindweed is native to the Mediterranean region, so that's where researchers concentrated their search for biological control agents that naturally attack the weed," Boldt said.
Before being brought to the U.S. by Boldt, the moth--like the mite--was tested in Europe to make sure it would attack only field bindweed and no crop or valuable U.S. plant. Boldt has been rearing the moth in his lab and will send some to Boydston for release in Washington.
USDA has maintained a research laboratory in Europe since 1919. Today, the ARS European Biological Control Laboratory, Montpellier, France, provides approximately 70 percent of all biological control agents introduced into the United States. The laboratory's studies and collections of Tyta and Aceria insects were done by Gaetano Campobasso in Italy and Javid Kashefi in Greece, respectively.
NOTE TO EDITORS: For details, contact Rick A. Boydston, Irrigated Agriculture Research and Extension Center, Agricultural Research Service, USDA, 24106 N. Bunn Rd., Prosser, WA 99350-9687, phone (509) 786-9267, fax (509) 786-9277, e-mail email@example.com. Paul E. Boldt, Grassland Soil and Water Research Laboratory, Agricultural Research Service, USDA, 808 Blackland Rd., Temple, TX 76501, phone (817) 770-6500, fax (817) 770-6561, e-mail firstname.lastname@example.org. Photos of both insects are available from Boldt.