July 15, 2003
Agricultural Research Service News
Promising New Compound for Fending Off Insects
A new chemical compound developed cooperatively by scientists with the Agricultural Research Service and the U.S. Department of Defense looks promising as the key active ingredient in new, safe insect repellents for U.S. military personnel and eventually for the general public. ARS has patented the new compound, called SS220, and it is currently undergoing toxicology tests required for registration with the U.S. Environmental Protection Agency.
ARS, UDSA?s chief in-house scientific research agency, has several specialized laboratories with expertise in studying biting insects such as mosquitoes, ticks and flies that can transmit diseases to humans.
DOD launched a Strategic Technology Objective three years ago to identify and develop a new standard military insect repellent to replace DEET, a repellent developed 50 years ago by ARS for the military. DEET is the most widely used repellent in the world and has prevented uncounted cases of malaria and other vector-borne diseases in both civilians and military. During the research project, researchers sought a new repellent effective against a wider range of mosquito species, and compatible with commonly used plastics such as in eyeglass frames and military equipment.
The Strategic Technology Objective involved representatives of the Department of Entomology of the Walter Reed Army Institute of Research (WRAIR) in Silver Spring, Md., and ARS? Chemicals Affecting Insect Behavior Laboratory (CAIBL), which is part of the ARS Henry A. Wallace Beltsville (Md.) Agricultural Research Center.
Entomologist Jerome A. Klun, who heads the CAIBL team working with the military?s infectious disease research program, collaborated with WRAIR?s Mustapha Debboun, a medical entomologist, to develop a clear, six-chamber device with which to safely screen candidate compounds on human volunteers? skin. Preliminary laboratory tests involved the controlled release of lab-reared, disease-free mosquitoes over treated skin to demonstrate the compound?s protective qualities. The team will now test the ingredient?s staying power through vigorous activity and exposure to water in the field. The initiative aims to further refine the cosmetic aspects of SS220 formulations.
SS220 is a highly effective chemical compound, called a stereo isomer, which Klun isolated from a mixture of compounds that was first synthesized by ARS scientists in 1978. CAIBL?s chemical team developed a three-step process which led to preparation of large quantities of SS220 required for testing.
The ARS Office of Technology Transfer (OTT) will license the USDA technology under policies set forth in the Federal Technology Transfer Act. Companies interested in licensing this USDA technology can obtain a license application online or from the OTT.
Tractor Tire Needs May Vary in No-Till and Conventional Farming Systems
Farmers who do not till their land may need different types of tractor tires in the future to minimize soil compaction, according to a study by the U.S. Department of Agriculture?s Agricultural Research Service (ARS).
Compaction is caused by the weight of the tractor tires pressing down on the soil. When operating tractors, farmers try to minimize compaction because it can hinder infiltration of water to crop roots and increase soil erosion and water runoff.
Thomas R. Way, an agricultural engineer with ARS?s National Soil Dynamics Laboratory in Auburn, Ala., led the study in cooperation with Tadashi Kishimoto at the Obihiro University of Agriculture and Veterinary Medicine in Japan. In the study, the researchers used a tractor tire equipped with six sensors on its tread to study tire pressure on tilled and no-till soils. Surprisingly, they found that the pressure was least uniform on untilled clay soils, and was actually more uniform on tilled soils.
This research is expected to help manufacturers adjust the tire contact pressure and the size of the tire lugs, which are the raised bars on the tread. The lugs have considerable contact with the soil and they also can affect compaction. Changing tire pressure and size could help minimize compaction on no-till fields, an important consideration because of the increasing popularity of no-till farming.
During the study, the researchers were also surprised by the similarity of another factor called ?tractive efficiency? on tilled and no-till soils. This is a measure of the efficiency with which the tire converts the power that?s applied to the wheel to useful work.
A tractor?s fuel efficiency increases with its tractive efficiency. Before the study began, the researchers thought that tractor fuel efficiency would be greater on no-till soils. However, the study showed that tractive efficiency was the same on tilled and no-tilled soils, meaning there was actually little difference in fuel efficiency.
New Tool on Tap for Fighting Listeria
A new tool could be at hand for ?subtyping? strains of Listeria monocytogenes bacteria that cause food-borne illness. A U.S. Department of Agriculture Agricultural Research Service (ARS) scientist and two Washington State University scientists have devised a technique called mixed genome microarray analysis to examine L. monocytogenes? DNA for genes that differ among its strains. Identifying the genes will help the researchers learn why some strains cause disease epidemics, while others do not. It also will help the scientists design subtyping methods for identifying the most pathogenic strains. These methods could then be used to check for genetic evidence of the strains in food, on farms or on food-processing equipment. Eventually the team hopes to parlay its microarray gene discoveries into a fast, standardized method of subtyping that public health labs can use to compare large amounts of data on strains that may cause local/and or national epidemics.
Scientists Explore Crop-Made Prebiotics to Bolster Gut Bacteria
Ongoing studies by ARS scientists suggest that making prebiotics from carbohydrates, using a new enzyme process, may expand markets for corn and other commodity crops. Prebiotics are complex carbohydrates such as short-chain sugars, called oligosaccharides, which pass undigested from the lower intestine to the colon. There, the carbs are consumed by Bifidobacterium, and other beneficial bacteria that release vitamins, minerals and nutrients that might not otherwise be available to their hosts ? human and animal. The bacteria may also change the colon environment so that pathogens like Salmonella are curtailed. In this case, an ARS chemist and cooperators found that an enzyme-based process for making alteran ?a promising bulking agent ? also yielded oligosaccharides that stimulate the growth of Bifidobacterium bacteria. This April, ARS applied to patent protection covering the synthesis and potential use of some of the prebiotics as food additives for both livestock and people.
Conservation Tillage: A Grower?s Drought Assistant
Conservation tillage continues to be good for the environment ? and can boost farmers? profits by helping them use water more efficiently, report ARS scientists. In test plots of cotton and peanuts in Georgia, conservation tillage limited rainfall runoff to less than 10 percent. In some cases, conservation tillage increased water infiltration into soil by up to 50 percent, compared to conventional tillage. Conventional plots also released five times more soil and rainfall runoff than conservation tillage plots, making a strong case for conservation tillage. The research indicates that a type of conservation tillage called strip-till not only reduces runoff, but increases water infiltration and appears to improve soil quality. In strip-till fields, narrow rows, four to six inches wide, are made for planting seed into the previous year?s plant- and cover-crop residue. Plant residues reduce water evaporation from the field and intercept raindrops from impacting directly on the soil surface, decreasing soil movement and cutting down on rain washing away pesticides and nutrients.
Turfgrass May be Carbon ?Sink?
The turfgrass found on golf courses, lawns and public parks may have a benefit hidden under the surface: It may serve as a ?sink? for storing carbon dioxide in the soil. Many ARS researchers have found that both rangeland and farmland can act as a carbon soil sink. In this process, some of the CO2 from the atmosphere is captured by plant photosynthesis and trapped in the soil, helping mitigate the greenhouse effect. In a recent study, ARS researchers studied 16 soil records from golf courses in the Denver area, some of which go back 45 years. They found that carbon sequestration lasts for up to 31 years in fairways and 45 years in greens, after which the rates slow or become negligible. The researchers also noticed that a rapid increase in carbon sequestration occurs in the first 25-30 years after the turfgrass is established. The study found that nearly a ton of carbon per acre per year is stored in the soil fairways and one ton per acre of carbon for greens.