Tiny black weevils might help stop the spread of a fast-growing water weed, Salvinia molesta, that’s infesting parts of eastern Texas. If the one-tenth-inch-long weevils, known as Cyrtobagous salviniae, perform as well in the United States as they have in countries such as Australia, South Africa and India, they might reduce the need for chemical controls. ARS scientists collected about 850 of the weevils in Florida and, with the help of colleagues from the Texas Parks and Wildlife Department, placed the insects at a salvinia-besieged lake and pond near Jasper, TX, and a reservoir at the Texas-Louisiana border. USDA's Animal and Plant Health Inspection Service helped fund the work. Weevil adults and young feed on the weed's nitrogen-rich buds. The alien weed has been found not only in Texas and Louisiana, but also in ponds in Alabama, Mississippi and South Carolina, a canal in Florida and a lake in Hawaii. It poses a threat to waterways in other warm-weather states, as well. It produces dense mats of small, oval, green to yellow-green leaves. The mats can double in size in only a few days. They crowd out native plants, ruin conditions for fish and wildlife, and interfere with flood control and irrigation as well as with fishing, swimming, boating and waterskiing. C. salviniae weevils showed up in Florida several decades ago and are thought to have a key role in keeping another salvinia species, S. minima, in check in that state. Scientists will monitor the weevils to determine if they flourish in their new surroundings.

ARS Aquatic Weed Control Research Laboratory, Ft. Lauderdale, FL
Ted D. Center, (954) 475-0541, ext. 103, tcenter@ars.usda.gov

Tiny parasitic wasps that biologically control crop-damaging caterpillars like bollworms may help locate hidden toxic chemicals, a joint study suggests. ARS, Iowa State University, and Oak Ridge National Laboratory are participating in a 4-year study, funded by the military’s Defense Advanced Research Projects Agency (DARPA). Under its “Controlled Biological Systems” program, scientists are studying whether the wasps can be used to sniff out chemical odors wafting from explosives like land mines, bombs, live rounds or even nerve toxins. It’s part of DARPA’s search for fast, nature-based means of monitoring the environment around military or civilian areas for chemical or biological threats, particularly from terrorist activity. Key to the approach: an ARS lab technique for training Micropletes, Cardiochiles and Cotesia wasps to associate synthetic odors with food (nectar) and egg hosts (caterpillars). Of particular interest are odors characteristic of cyclohexanol and trinitrotoluene (TNT). Both chemicals are common ingredients in explosives. Flight tunnel experiments show the wasps will zeroin on tubes dispensing the chemicals at a rate of 0.05 to 30 nanograms per minute, about 3-feet downwind. That’s equivalent to a drop of water in an Olympic pool. Scientists will also explore practical, cost-effective methods of using the wasps for detecting harmful chemicals.

Insect Biology and Population Management Research Laboratory, Tifton, GA
Joe Lewis, (912) 387-2369, wjl@cpes.peachnet.edu