When sterile Mediterranean fruit flies are recruited to keep their wild, fertile counterparts from getting established in warm weather states like California and Florida, a special strain of sterile medflies called Toliman TSLs may be the best for this important assignment. Six years of tests by USDA scientists and their colleagues in the lush coffee plantations of southwestern Guatemala have shown for the first time that Toliman TSL sterile medflies may be anywhere from three to five times more effective than conventional strains of sterile medflies. When invading medflies are detected on the mainland United States, sterile male medflies—mass-reared by the millions—are dropped from airplanes to find and mate with wild females. Because no offspring result, the population dies out. Medfly, or Ceratitis capitata, can infest more than 250 different kinds of fruits, vegetables, and nuts, and easily cost millions of dollars to eradicate. Toliman TSLs are temperature-sensitive, lethal medflies, meaning that high temperatures can be lethal to eggs containing TSL females. The TSL trait allows mass-rearing of medflies that are exclusively males, thus saving the cost of producing unneeded females. Also, not having sterile females to distract them once they are outdoors and looking for wild, fertile females may be a key to the TSL males’ success. Insectary workers produce TSL males by bathing medfly eggs in 97 degree F water for 12 to 24 hours. That kills all of the eggs with female embryos inside but doesn’t harm the males. Mass-rearing facilities in Hawaii and Guatemala that produce sterile male medflies for use in the mainland United States plan to begin producing TSL steriles exclusively.

U.S. Pacific Basin Agricultural Research Center, Honolulu, HI
Donald O. McInnis, (808) 988-8232, dmcinnis@pbarc.ars.usda.gov

Application costs for boll weevil eradication could be reduced by adding refined cottonseed oil to malathion sprays. The boll weevil, a cotton pest, has caused billions of dollars in damage, crop losses, and control costs since entering the United States in the late 19th century. For this reason, USDA started the Boll Weevil Eradication Program in 1978 to help farmers battle this pest. The first year of the program begins in a particular area in August and continues into October. During this time, growers spray 8 to 12 applications of malathion to reduce the number of weevils entering diapause—the dormant period in their life cycle. The researchers found that, during July, boll weevil mortality from an 8-ounce mixture of malathion and cottonseed oil was the same as from a 10-ounce application of undiluted malathion for the first 2 days after application. In August, however, there were no differences in mortality until 5 days after application. The research also showed that malathion accumulates on the surface of mature cotton plants after repeated application during rain-free periods in August, implying that the interval between applications could be increased during this part of the growing season, thus reducing the number of applications and eradication costs. The 8-ounce mixture of malathion/cottonseed oil is cheaper by 20 cents per acre per application than a 10-ounce application of malathion—a substantial cost reduction.

Application and Production Technology Research Unit, Stoneville, MS
Joseph E. Mulrooney, (662) 686-5342, jmulrooney@ars.usda.gov

Forensic plant pathologists investigating the fungus that caused the Irish potato blight are using biotechnology to aid in their sleuthing. In 1845, a fungus called Phytophthora infestans devastated the Irish potato crop. The population of Ireland was almost halved—from 8.2 million to 4.4 million—because of disease, starvation, and emigration. Hundreds of thousands of people emigrated to America. Now, researchers at ARS and North Carolina State University at Raleigh are examining the past to find clues about the fungus’ future. They have studied DNA from more than 66 herbarium samples of potato and tomato lesions to uncover information about the sexual state of the fungus. Looking for the fungus’ fingerprints, the scientists developed PCR primers to amplify DNA from the samples. So far, 20 of the samples have tested positive for the fungus, including an Irish specimen collected in 1846, British samples collected in 1845, 1846, and 1847, and samples from the USDA-ARS National Fungus Collection.

New England Plant, Soil, and Water Laboratory, Orono, ME
Carol L. Groves, (207) 581-3366, cgroves@maine.edu

Chemical cues in the saliva of tobacco budworm and corn earworm caterpillars cause plants to send out defensive signals when the caterpillars chew on them. Small wasps, natural enemies of the caterpillars, then follow the defensive signals to find and sting the caterpillars. The larvae of the budworm, Heliothis virescens, and earworm, Heliocoverpa zea, are a major problem in cotton crops, as well as in corn, soybeans, sorghum, sunflowers, tobacco, and peanuts. Building on previous research findings that beet armyworm caterpillars elicit a chemical SOS response in plants, ARS researchers were surprised to find that budworms and earworms produce the same compounds present in the saliva of beet armyworms. Oddly, plants are able to distinguish which insect is nibbling on their leaves and give off the proper distress signal to attract that insect’s natural enemy. The scientists hope that by studying plant-insect interactions, they can develop plant varieties with more powerful chemical defenses against insect pests.

Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL
Naoki Mori/James H. Tumlinson, (352) 374-5731, tumlinson@gainesville.usda.ufl.edu

Besides herbicides, the best way to prevent the spread of the noxious weed tropical soda apple, Solanum viarum, is to remove the plant and burn it. Tropical soda apple now covers about 1.5 million acres in the U.S. Southeast, having been spread primarily by cattle, but also by deer and other wildlife. These animals love to eat the fruit. It passes through their digestive tract, and the seeds are then spread in the feces. The weed can be found growing in pastures, urban areas, vegetable crops, and natural areas in Florida, Georgia, South Carolina, North Carolina, Tennessee, Alabama, Mississippi, and Louisiana. It has also been found in Puerto Rico. ARS researchers warn not to burn tropical soda apple in a home oven or microwave, because the plant and its fruit produce glyco-alkaloids, a substance toxic to humans. The best cultural practice for homeowners is removing single plants by hand or clipping or mowing multiple plants. Mowing the weeds several times early in the season and mid-season helps prevent fruit and seed production. Farmers, landowners, and homeowners can obtain 80 to 90 percent control by mowing every 45 to 60 days. Once the plant is full of fruit, however, mowing could spread seeds. ARS researchers caution that people should contact a county extension agent first to identify the weed and then to eradicate it as soon as possible.

Weed Science Research Unit, Stoneville, MS
Charles T. Bryson, (601) 686-5259, cbryson@ag.gov

Several chemical scents that attract Colorado potato beetles have been discovered by ARS scientists. The beetles are the potato crop’s most destructive pest, costing growers millions of dollars in chemical control and crop losses. For at least 73 years, scientists have been searching for the scent that attracts this yellow-and-black bug to solanaceous plants. In laboratory tests, when the beetles were offered a choice between one of the newly discovered scents and potato foliage, they were confused and could not tell the difference. The researchers use tiny electrodes attached to the tips of the beetles’ antennae to monitor the pests’ sensitivity to the potatoes’ scent. In preliminary field tests, the beetles were captured with a synthetic lure containing a mixture of these compounds—something never done before. The scientists have identified at least five synthetic blends that are attractive to the insects in laboratory tests and that may be attractive in the field as well. This research could result in the use of naturally occurring chemical signals to monitor and control pest populations. Researchers plan on using this information to investigate how chemical scents, which are emitted when the beetles chew on plants, might help attract potato beetle predators.

Vegetable Laboratory, Beltsville, MD
Joseph C. Dickens, (301) 504-8957, jdickens@asrr.arsusda.gov

New strategies for controlling rosette disease in blackberries could open new avenues for small farmers. Rosette, or double blossom, is one of the most severe fungal diseases of blackberries grown in the southeastern United States. Many blackberry crops fall prey to the disease, which reduces yields and fruit quality. ARS researchers found that applying four fungicide applications at 10- to 14-day intervals, beginning about 6 weeks before berries ripen and continuing until 3 days before harvest, controls the disease. They also recommend making a fifth application immediately after harvest. In the past, farmers have been disappointed with fungicide treatments, because they thought spraying would control the disease in that year’s crop. But that’s not the case; fungicides applied this year help control next year’s rosette problem. Benomyl is the most effective fungicide tested for controlling rosette, which is caused by the fungus Cercosporella rubi. Few fungicides are registered and available for controlling blackberry diseases. ARS researchers plan to evaluate some new fungicides for controlling rosette. The disease is one of the major reasons southeastern farmers don’t grow this specialty crop, which can yield $3,000 to $4,000 an acre. Overcoming rosette would offer a high-value crop that costs less to establish than strawberries and blueberries.

Small Fruits Research Station, Poplarville, MS
Barbara J. Smith, (601) 795-8751, bjsmith@ag.gov

A natural protein called avidin, found in egg whites, is being developed into a new biopesticide in a partnership between ARS researchers and a Texas agricultural biotechnology company. The first scientific studies of the protein’s lethal effect on stored-product insects were conducted by ARS researchers in the early 1990s. Avidin binds up biotin, an essential vitamin for insect growth, creating a vitamin deficiency that stunts the insects’ growth or kills them. More recently, ARS scientists demonstrated the toxicity of transgenic avidin corn to most insect pests that damage grains during storage. When present in corn seeds at about 100 parts per million, avidin prevents development of the maize weevil, lesser grain borer, warehouse beetle, sawtoothed grain beetle, red flour beetle, confused flour beetle, flat grain beetle, Indianmeal moth, Mediterranean flour moth, and Angoumois grain moth. Only one species, the larger grain borer, tolerates the protein. ProdiGene, Inc., College Station, TX, produces the transgenic corn containing avidin. Avidin is relatively nontoxic to animals and humans.

Grain Marketing Production and Research Center, Manhattan, KS
Karl Kramer, (785) 776-2711, kramer@usgmrl.ksu.edu

A wild Mexican cousin of the potato may be a good source of resistance against Phytophthora infestans, the fungus that causes late blight and resulted in the Irish potato famine. ARS researchers have crossed a heretofore uncrossable bridge: mating a wild Mexican species—Solanum pinnatisectum—with a derivative of a commercial potato variety, using a technique known as embryo rescue. A hybrid from the rescue can serve as a parent in a subsequent mating with the cultivated potato. A second technique has helped to further open up the gene pool from wild Mexican species. The researchers crossed S. verrucosum, which is compatible with derivatives of common varieties, with the same group of Mexican uncrossable species. This mating yielded several new hybrids, which have been crossed to a range of wild relatives and to derivatives of common varieties. The techniques represent two ways to make new hybrids via sexual means and incorporate them into the commercial potato. Using fungicides to control recent late blight attacks has sharply increased production costs by nearly $200 an acre for potato growers in Idaho, Washington, North Dakota, Colorado, Oregon, Minnesota, Michigan, Maine, and Wisconsin. Some new strains of late blight have emerged that are resistant to what used to be the most effective fungicide, metalaxyl.

Vegetable Crops Research, Madison, WI
Robert E. Hanneman, Jr., (608) 262-1399, rehannem@facstaff.wisc.edu