UC Davis News: Agriculture

Horse Day Symposium, Farrier's Workshop Address Industry Challenges

Tue, 30 Sep 2008 00:00:00 -0700

Horse enthusiasts from throughout the state will gather Saturday, Oct. 4, for the campus's annual Horse Day Symposium, featuring topics such as racehorse injuries, recognizing and rehabilitating neglected horses, appropriate feed, hoof problems, and financial aspects of horse ownership.

A Farrier's Workshop also will be held Sunday, Oct. 5, on campus.

The symposium and workshop are designed to provide horse owners and horseshoers with the latest information on horse health and care, with presentations given by experts from UC Davis, Cal Poly Pomona, and private organizations. The symposium presentations are intended for horse fanciers age 12 years and older.

Registration will begin Saturday at 7:15 a.m. in Freeborn Hall at UC Davis, and talks will be presented from 8 a.m. to 2:30 p.m., with a noon lunch break. Attendees will have a chance to meet with exhibitors during coffee breaks and lunch.

At 3 p.m., Horse Day participants can attend a demonstration by the San Joaquin Valley Rangers Cowboy Mounted Shooting Group or take a tour of UC Davis' William R. Pritchard Veterinary Medical Teaching Hospital.

The cowboy mounted shooting performance will showcase a sport that combines elements of a wild-west show with barrel racing, pole bending, reining and many other equestrian skills. These are performed while using two .45-caliber single-action revolvers, loaded with black powder blanks to shoot balloons. The demonstration will be presented in the Animal Science Horse Barn Arena.

The Sunday Farrier's Workshop will feature lectures in the morning in Meyer Hall, covering the anatomy and physiology of the foot as well as major problems such as navicular disease and laminitis. In the afternoon, attendees will participate in a wet lab at the Animal Science Horse Barn in which they will have a hands-on opportunity to trim and shoe a foot based on the horse's leg and foot anatomy.

Registration is $30 per person for the Saturday Horse Day events. The fee for the Sunday Farrier's Workshop is $150 per person for both the lecture and lab or $50 for the lecture only.

More information about the days' activities is available online at http://animalscience.ucdavis.edu/events/horseday/2008/default.htm or by contacting the animal science department at (530) 752-1250.

UC Davis Researcher Maps Genes of Destructive Parasite

Tue, 30 Sep 2008 00:00:00 -0700

The genome sequence and genetic map for a microscopic, soil-dwelling worm that is one of the world's most common and destructive plant parasites has been completed by a research team, including UC Davis nematology professor Valerie Williamson.

The tiny worm, whose scientific name is Meloidogyne hapla, is more commonly known as the northern root-knot nematode. Together with related species, it annually causes an estimated $50 billion in plant damage, afflicting crops ranging from alfalfa to potatoes to grapes.

The findings of the group, led by researchers Charlie Opperman and David Bird at North Carolina State University, were recently published online in the Proceedings of the National Academy of Sciences. The sequence data have been deposited in public databases so that other researchers around the world can use the data to discover more specific information about the parasite.

"We are hopeful that this information will lead to the development of more environmentally friendly tools for managing this species and other root-knot nematodes," said Williamson, whose laboratory developed the genetic map for this project.

The northern root-knot nematode has become a key model species in the study of plant-parasitic nematodes, and the completion of the genetic map and genome sequence will equip researchers to ask highly specific questions about the evolution and nature of parasitism.

This study was funded by a grant from the National Science Foundation to UC Davis and a grant from the U.S. Department of Agriculture to North Carolina State University.

Poultry Topics Spotlighted During Oct. 4 Avian Science Day

Tue, 30 Sep 2008 00:00:00 -0700

Poultry hobbyists from throughout northern California will gather Saturday, Oct. 4, for Avian Science Day at UC Davis.

The free, public event offers backyard poultry enthusiasts the latest information on breeding and caring for chickens, turkeys and other poultry species.

Speakers will discuss poultry breeding, raising heritage turkeys, avian influenza, market poultry, interpreting diagnostic reports and how to become a poultry veterinarian. The last session of the day will address ethics certification, required for all exhibitors of market poultry and eggs at the 2009 California State Fair.

Speakers for the day will include James Hermes, a Cooperative Extension poultry specialist from Oregon State University; the Thode family of Santa Rosa; Fred Leung, a zoology professor and poultry expert from the University of Hong Kong; Jeanne Marie Smith, a poultry veterinarian at the California Animal Health and Food Safety Laboratory at UC Davis; and Francine Bradley, a Cooperative Extension poultry specialist in UC Davis' Department of Animal Science and coordinator of Avian Science Day.

Participants are encouraged to bring a sack lunch to eat during the noon break, when Bradley will talk about the birds and wildlife she encountered during travels in New Zealand and Australia.

The day will begin at 8 a.m. with registration in 2205 Haring Hall, located on Hutchison Drive. Campus parking, free on weekends, will be available across the street in Lot 43.

For more information on Avian Science Day, contact the Department of Animal Science at (530) 752-9040.

Media Calendar: Local Food Systems Symposium

Tue, 30 Sep 2008 00:00:00 -0700

Dec. 2-3, Tuesday and Wednesday -- This symposium will showcase local food systems projects funded by the statewide UC Sustainable Agriculture Research and Education Program (SAREP), an affiliate of the UC Davis Agricultural Sustainability Institute (ASI). These projects demonstrate how partnerships and marketing opportunities can be created in new ways, linking consumers, distributors and producers in rural and urban areas. Cooperative Extension personnel, researchers, government agencies, nonprofits, farmers and community members are invited to share information, network and learn about regional food systems activities. Paul Muller of Full Belly Farm will be the keynote speaker. The event is co-sponsored by SAREP; ASI; UC Agriculture and Natural Resources, North Coast and Mountain Region; and the California Communities Program, a Cooperative Extension unit of the UC Davis Department of Human and Community Development. It will be held in the Buehler Alumni and Visitors Center at UC Davis. More information is available online at: http://www.sarep.ucdavis.edu/cdpp/lfs08/.

Wine Industry Intent on Truly Going Green

Fri, 26 Sep 2008 00:00:00 -0700

Robert Smiley, professor and director of wine studies in the UC Davis Graduate School of Management, discussed his findings this week at the annual Wine Industry Financial Symposium in Napa, Calif.

Those surveyed ranged from growers to vintners to distributors. Many said their firms were actively engaged in environmentally friendly business activities, such as package redesign, use of biodiesel fuel, wastewater reclamation and developing "green" building plans.

Eighty percent of the vineyard representatives said they have used sustainable farming practices on at least part of their acreage during 2008. And nearly half said they have been, or plan to be, marketing their grapes as "sustainable" or "organic" during the current or upcoming year.

They expressed a concern, however, over the lack of clarity in the industry and among consumers over what many environmental terms like "sustainable," "green," and "low carbon footprint" actually mean and how industry can genuinely adopt environmentally sensitive practices.

Results of both the wine executives and wine professionals surveys are available online at http://www.gsm.ucdavis.edu/2008winestudy.

As part of their ongoing support for the California wine industry, the Graduate School of Management and the UC Davis Department of Viticulture and Enology will offer the 2009 Wine Executive Program March 8-12 in Sacramento. The four-day program will focus on the management skills necessary to be profitable in the wine industry. Information about the program is available online at http://www.wineexecutiveprogram.com.

Centennial Harvest Celebration set for Wolfskill Ranch

Thu, 25 Sep 2008 00:00:00 -0700

UC Davis olive oil and vinegar will be just part of a diverse spread of regionally produced foods showcased in a luncheon Saturday, Oct. 11, during the Centennial Harvest Celebration at the university's historic Wolfskill Ranch in Winters.

The public is invited to join in the event from 10:30 a.m. to 2:30 p.m. Seating is limited and advanced ticket purchase is required for the harvest celebration, which is co-sponsored by the UC Davis Olive Center, Slow Food Yolo, and Yolo County Agricultural Marketing Initiative.

"As UC Davis celebrates its 100th anniversary, it's quite fitting that we who live so close to the heart of California agriculture should take time, especially at harvest, to taste the finest our land has to offer," said Dan Flynn, executive director of the UC Davis Olive Center. "This is also a special opportunity to gather with others in the area who have a special interest in food and its relation to the quality of life."

The celebration will include a tour of the Wolfskill Ranch orchards, a tasting of Yolo and Solano olive oils, and dining beneath the ranch's 150-year-old olive trees.

Local products to be served include roasted Capay Valley lamb, rosemary and sea salt flavored almonds, figs stuffed with walnuts, leek gratin, roasted mixed peppers, local greens, walnut and almond pies, and dried-apricot tarts. Cabernet Sauvignon made from the university's Napa Valley vineyard will be donated by the UC Davis Department of Viticulture and Enology, and other local wines also will be served.

Celebration participants also will receive a $29 bottle of UC Davis Centennial Olive Oil to take home. The oil, specially blended for the occasion, combines UC Davis Olive Oil with the oils of some of California's finest producers including California Olive Ranch, Saltonstall Estate, McEvoy Ranch, Dry Creek Olive Co., Pasolivo and Corto Olive.

The Wolfskill Ranch is located at 4339 Putah Creek Road in Winters. Tickets costing $90 each for Slow Food members and $100 per person for nonmembers are available online at http://www.brownpapertickets.com or from the Davis Food Coop in Davis or Steady Eddy's in Winters.

Rice Protein Identified that Moderates Resistance to Infectious Disease

Tue, 23 Sep 2008 00:00:00 -0700

Researchers at the University of California, Davis, have identified a plant protein that is a key player in moderating resistance to infectious disease. The discovery has significant implications for medical and agricultural researchers, particularly those working to improve global rice production.

The protein, called XB15, keeps the plant's immune response from overreacting and damaging the plant.

Findings from the study, led by UC Davis rice geneticist Pamela Ronald, were published today in the journal The Public Library of Science Biology.

For more than 20 years, Ronald and her colleagues have been working to better understand the genetics behind how rice plants respond to the environment. They have developed rice plants that can better withstand environmental stresses, such as flooding and infectious diseases.

In 1995, the Ronald lab identified a protein in rice that serves as a "pathogen recognition receptor." Such receptors are proteins found in virtually all higher organisms and are key to controlling the plant and animal response to infection. The researchers found that this particular receptor in rice -- known as XA21 -- was very similar to proteins in humans and other animals that control the innate immune response.

While such immune responses are critical to the survival of the plant or animal, they do come at a cost. In fact, in humans, the failure to regulate these responses can lead to various diseases, including some cancers.

Scientists have found that most plants or animals have built-in biochemical moderators, known as negative regulators, which keep an organism's immune response in check. These negative regulators make sure that a defense against a perceived pathogen is only mounted when truly needed.

In this recent study, Ronald and her colleagues identified a negative regulator for the XA21 pathogen recognition receptor -- a protein they named XB15.

"This finding gives us a better understanding of how the innate immune response is controlled," said Ronald, who chairs UC Davis' Plant Genomics Program.

Ronald and colleagues have shown that rice plants carrying an altered XB15 protein have enhanced resistance to bacterial leaf blight, which causes a serious bacterial disease of rice. They also discovered that if this protein is excessively produced in rice plants carrying the XA21 resistance gene, it could actually compromise the plant's ability to defend against the disease.

"This information should help us to develop hardier, more productive rice plants that can better meet the worldwide demand for rice," Ronald said. She noted that in parts of Asia, bacterial leaf blight has been known to reduce annual rice yields by as much as 60 percent.

"Rice is the staple food for more than half the world's population," Ronald said. "In developing countries, such significant crop losses translate directly into human suffering."

Collaborating on this study with Ronald were Chang-Jin Park, Ying Peng, Xuewei Chen, DeLing Ruan, Patrick E. Canlas and Rebecca Bart, all of UC Davis, and Christopher Dardick, formerly of the Ronald lab and now at the U.S. Department of Agriculture's Appalachian Fruit Research Station in Kearneysville, W.Va.

This study was funded by the National Institutes of Health, the U.S. Department of Agriculture and the Korea Science and Engineering Foundation.

Wine Industry Intent on Truly Going Green

Mon, 22 Sep 2008 00:00:00 -0700

The wine industry is making a concerted effort to adopt environmentally responsible practices but sees a need for better education among both consumers and professionals on many "green" issues, according to two surveys of wine industry professionals and executives conducted by Robert Smiley, professor and director of wine studies in the Graduate School of Management at the University of California, Davis.

"These industry leaders are very concerned that their firms authentically 'walk-the-walk' when it comes to environmental issues and that they not be accused of just 'greenwashing' their businesses," Smiley said.

He added that while survey participants reported that the high prices of gasoline and other inputs have negatively impacted their costs and revenues, they remain optimistic that the industry will ride out the current nationwide economic downturn.

Smiley will report his findings from the recent surveys at 8:30 a.m. Tuesday, Sept. 23, during the Wine Industry Financial Symposium to be held at the Napa Valley Marriott in Napa, Calif.

Survey of wine executives

As part of his 10th annual wine executives survey, Smiley gathered the opinions and projections of 28 heads of key wine operations, ranging from growers to vintners to distributors.

All of the executives interviewed said their firms were actively engaged in environmentally friendly business activities, such as package redesign, use of biodiesel fuel, wastewater reclamation and developing "green" building plans. They expressed a concern, however, over the lack of clarity in the industry and among consumers over what many environmental terms like "sustainable," "green," and "low carbon footprint" actually mean and how industry can genuinely adopt environmentally sensitive practices.

Survey respondents also said that rising prices for gas, electricity, supplies and transportation have significantly raised the cost of doing business across the industry at the same time that wine consumption has been hurt by the general economic downturn. They reported that consumers are responding to rising gas and food prices by dining out less and buying less wine, and noted that wine sales at both casual and high-end restaurants have suffered as a result.

"Despite that downturn in sales, the majority of the wine executives surveyed said that they believe the industry will survive the current economic slump on the strength of nonrestaurant sales, particularly the moderately priced $10-$14 wines," Smiley said. "They are confident that the millennial generation's love of wine provides a solid foundation for the industry."

Respondents to the executive survey also reported that:

Consolidation of distributors is not having a significant impact on large wine producers but is making it difficult for small- to medium-sized wineries to gain a market share.
There is, or likely will be, a grape shortage in Napa and Sonoma counties, especially of major varietals such as Cabernet Sauvignon and Pinot Noir.
There is concern that some Central Valley growers will replace wine grape vineyards with other crops.
Major changes in wine packaging during the next five to 10 years are anticipated, with most producers using screw caps rather than corks and less expensive wines being sold in soft-sided packages rather than bottles.

Survey of wine professionals

Smiley's survey of wine professionals, now in its 17th year, included responses from 73 vineyard and winery representatives from throughout California.

"One of the biggest changes reflected in this survey was that consumers are increasingly viewing wine as an integral part of a healthy lifestyle," said Smiley. "And for the first time, these wine professionals said that they are finding consumers to be more accepting of alternative packaging."

This survey, like the wine executives survey, also reflected a marked increase in businesses using sustainable practices. Eighty percent of the vineyard representatives participating in the survey said they have used sustainable farming practices on at least part of their acreage during 2008. And 46 percent of the respondents said they have been, or plan to be, marketing their grapes as "sustainable" or "organic" during the current or upcoming year.

Survey participants from vineyard operations also reported that they are reducing their use of vineyard chemicals and mechanized equipment to deal with the rising cost of inputs.

They predicted that the growing consumer perception of wine as an everyday beverage and the rising quality of California wines relative to their prices are the top factors that will impact California wine sales during the next three years. Growing recognition of the health benefits of wine, as well as the deregulation of direct shipping of wine, will likely also provide short-term boosts for the industry, they projected.

And for the first time, survey participants from the winery side of the industry noted that their firms are planning to introduce new, lighter-weight packaging for their wines.

Results of both the wine executives and wine professionals surveys are available online at http://www.gsm.ucdavis.edu/2008winestudy.

As part of its ongoing support for the California wine industry, the Graduate School of Management and the UC Davis Department of Viticulture and Enology will offer the 2009 Wine Executive Program March 8-12 in Sacramento. The four-day program will focus on the management skills necessary to be profitable in the wine industry. Information about the program is available online at http://www.wineexecutiveprogram.com.

'Good Life Garden' Explores Home-Grown Food

Mon, 22 Sep 2008 00:00:00 -0700

The UC Davis Good Life Garden, located at the Robert Mondavi Institute for Wine and Food Science, will host its debut event featuring David Howard, Prince Charles' former head gardener and one of the world's foremost experts on organic and sustainable horticulture, Saturday, Sept. 27.

Registration for the public event will begin at 4:30 p.m. at UC Davis' Sciences Lecture Hall. The program will last from 5 p.m. to 7:30 p.m., including a "Taste of the Region" food sampling. Program information and tickets, costing $75 per person, are available through the Good Life Garden Web site at: http://www.goodlifegarden.ucdavis.edu/events.

In addition to Howard, guest speakers will be author and food historian Ethne Clarke, discussing the evolution of the kitchen garden from the late medieval period to the 19th century, and local author, cooking school owner and Slow Food leader Georgeanne Brennan.

Brennan will speak at 5 p.m., discussing how to create and maintain a kitchen garden that is both aesthetically pleasing and productive year-round.

Clarke will speak at 5:30 p.m. about contemporary home food production from a historical standpoint.

The 6 p.m. "Taste of the Region" will feature a wide array of regional farm-raised and handcrafted foods, wine and beer. Attendees will taste products ranging from heirloom tomatoes and wine grapes to caviar, cheeses, bread, chocolate and smoked fish.

At 7 p.m., horticultural expert Howard will discuss the gardens at Highgrove House in Gloucestershire, England, Prince Charles' private residence.

The Robert Mondavi Institute's Good Life Garden celebrates the relationship between good food and good health by linking the culinary arts, nutrition, and wine and food sciences in an academic setting. It will offer year-round public events, workshops, internships and volunteer opportunities.

Academy Aims to Train Global Cadre of Plant Breeders

Tue, 09 Sep 2008 00:00:00 -0700

An international group of working professionals from 10 different countries is getting a jump on the fall quarter at UC Davis, arriving early to begin the second class of the Plant Breeding Academy, designed by the campus's Seed Biotechnology Center.

The center developed the academy in direct response to industry concerns over a decline in the number of plant breeders being trained in academic programs. The academy was designed to enable companies to provide their employees with formal instruction in genetics, statistics and plant breeding theory, while they remain in their current jobs.

"Overall, this course is invaluable to me in that I am able to maintain my full-time, great job, and gain this knowledge without having to become a full time student," wrote academy graduate Peter Martini.

The 23 participants, from as far away as Africa, Australia, Chile and Europe, will spend more than 300 hours in classes, workshops and the field. The two-year professional development program, which includes six weeklong sessions at UC Davis, offers advanced training to prepare these students to become independent plant breeders.

After the first week, which ends Saturday, Sept. 13, participants will return to their home companies or research institutions to continue studying and put their new skills into practice. They are slated to come back to UC Davis for one-week classes in February and again in June, with a similar program scheduled for the second year of the academy.

Now welcoming its second class, the academy hosted its inaugural class of 15 students from three countries between September 2006 and June 2008. Upon completing the program, students received a certificate and 19 units of academic credit. They should be equipped to work as independent plant breeders or direct regional plant-breeding programs.

Academy courses are taught by internationally recognized plant breeders Doug Shaw and Larry Teuber, both of UC Davis, and Todd Wehner from North Carolina State University, with guest lecturers speaking on their specific areas of expertise.

Coursework covers all aspects of plant breeding, including genetics; statistics; single-trait selection; recombination and population development; resistance breeding; genotype by environment interactions; biotechnology; data management; finishing varieties; and seed production, conditioning and storage. Each student designs a breeding program as a final project for the academy.

More information about the academy program can be found online at: http://pba.ucdavis.edu.

Jared Diamond to Open International Genetic Diversity Symposium

Wed, 27 Aug 2008 00:00:00 -0700

Evolutionary biologist and author Jared Diamond will present the opening keynote address for an international symposium on agricultural biodiversity, to be held Sept. 14-18 at the University of California, Davis.

The Harlan II International Symposium, the successor to a program held 11 years ago in Syria, is dedicated to the late crop evolutionist Jack R. Harlan. It will focus on the importance of using and conserving not just a diversity of species, but also genetic diversity within species.

In opening the symposium, Diamond will discuss whether environmental factors, rather than pure chance, led to the uneven distribution around the world of plant and animal species suitable for domestication and agricultural use. His public presentation on Sunday, Sept. 14, will begin at 6:15 p.m. in 123 Science Lecture Hall at UC Davis. Admission to the talk and the preceding reception will cost $50 per person.

Diamond maintains that the adoption of agriculture was "the most important event in the last 50,000 years of human history." As people developed the ability to cultivate crops and raise animals, they were able to produce a surplus of food, which fueled population growth and led to settled living, technology, social stratification and political centralization, he notes.

He points out that the societies with the greatest variety of plant species suitable for farming expanded earlier and farther than did societies in areas with the fewest farmable plant species -- and no animal species -- that were easily domesticated. For example, cultures in the Fertile Crescent, China, the Andes, and Meso-America -- the land between central Mexico and Nicaragua -- flourished, while cultures in areas such as Eastern North America and Highland New Guinea did not.

Diamond will question whether environmental factors in different regions predisposed wild animal and plant species in those areas to develop traits conducive to domestication.

A complete program for the Harlan II symposium is available online at: http://harlanii.ucdavis.edu/main/speakers_topics.htm. For fee information and a list of talks and tours, click on "registration" at the left of this page.

Among the speakers during the three-day symposium will be:

Monday, Sept. 15, 9 a.m. -- Robert Wayne, a UCLA biology professor and expert on canine genetics, will discuss what the analysis of the dog genome -- the entire collection of genes for the animal family that includes domestic dogs, wolves, foxes and coyotes -- tells about the evolutionary history of these animals and how the various species are related.

Monday, Sept. 15, 1:30 p.m. -- Doyle McKey, Universite de Montpellier II and the Center of Evolutionary and Functional Ecology, Montpellier, France, will discuss ecological approaches to crop domestication, using manioc, or cassava, as an example of how ecology can be integrated with genetics and ethnobiology -- the study of how people interact with the living environment -- to test plant-domestication scenarios.

Tuesday, Sept. 16, 9:30 a.m. -- Anthropologist Melinda Zeder, director of the archaeobiology program for the Smithsonian National Museum of Natural History, will discuss her latest research on when and where in the world animals were first domesticated.

Tuesday, Sept. 16, 6 p.m. -- Keynote speaker Gary Nabhan, an ecologist and pioneer in the local-food movement from the Southwest Center of the University of Arizona, will compare the crop diversity found by plant explorer N.I. Vavilov between 1916 and 1936, with the remaining diversity that Nabhan found in the same areas in nine countries on five continents three quarters of a century later. Nabhan says that an understanding of how biodiversity in local agricultural systems has changed may help predict how well farmers may be able to adapt to rapid climate change, globalization, water scarcity, and weed or pest invasions.

Wednesday, Sept. 17, 8 a.m. -- M. Kat Andersen, a plant ecologist in UC Davis' Department of Plant Sciences and the U.S. Department of Agriculture's Natural Resources Conservation Service, will discuss how Native Californians cultivated naturally occurring plants as sources of food even before the first Europeans arrived and how some of those practices are being applied in certain sectors of modern agriculture today.

Wednesday, Sept. 17, 9 a.m. -- Dennis Hedgecock, a fisheries ecologist at the University of Southern California, will discuss the importance of conserving genetic resources in aquaculture, which he says is now the fastest-growing sector of global food production. He will discuss the challenges in both conserving and utilizing the planet's imperiled aquatic biodiversity, when faced with the threat of overfishing, species introductions, interactions of wild and farmed stocks, ocean warming and ocean acidification.

Wednesday, Sept. 17, 11 a.m. -- Charles Bamforth, the Anheuser-Busch Endowed Professor of Brewing Science at UC Davis, will discuss genetic resources of brewing yeast, which he says is the best example of the major advances that have been made in just a few decades in understanding the physiology, biochemistry and genetics of yeasts and other microorganisms.

Wednesday, Sept. 17, 11:30 a.m., -- James Lapsley, adjunct associate professor in the Department of Viticulture and Enology and chair of the Department of Science, Agriculture, and Natural Resources in UC Davis Extension, will talk about the introduction to California of Vitis vinifera, the grape species that includes most traditional European wine grapes. Lapsley is author of the book "Bottled Poetry," a history of California winemaking.

News media who would like to attend all or parts of the symposium free of charge should RSVP to Pat Bailey, News Service, (530) 752-9843, pjbailey@ucdavis.edu.

Groundbreaking Research Shows DEET Not Sweet to Mosquitoes

Mon, 18 Aug 2008 00:00:00 -0700

Spray yourself with a DEET-based insect repellent and the mosquitoes will leave you alone. But why? They flee because of their intense dislike for the smell of the chemical repellent and not because DEET jams their sense of smell, report researchers at the University of California, Davis.

Their groundbreaking findings were published today in the Proceedings of the National Academy of Sciences (PNAS).

"We found that mosquitoes can smell DEET and they stay away from it," said noted chemical ecologist Walter Leal, professor of entomology at UC Davis. "DEET doesn't mask the smell of the host or jam the insect's senses. Mosquitoes don't like it because it smells bad to them."

DEET, the common name for N,N-diethyl-3-methylbenzamide, is the most common active ingredient in insect repellents. Developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, DEET is considered the "gold standard" of insect repellents. Worldwide, more than 200 million people use DEET to ward off vectorborne diseases.

But DEET's mode of action or how it works has puzzled scientists for more than 50 years. Scientists long surmised that DEET masks the smell of the host, or jams or corrupts the insect's senses, interfering with its ability to locate a host. Mosquitoes and other blood-feeding insects find their hosts by body heat, skin odors, carbon dioxide (breath), or visual stimuli. Females need a blood meal to develop their eggs.

Leal said previous findings of other scientists showed a "false positive" resulting from the experimental design.

Entomologist Jim Miller of Michigan State University praised the UC Davis researchers' work as correcting "long-standing erroneous dogma."

"For decades we were told that DEET warded off mosquito bites because it blocked insect response to lactic acid from the host -- the key stimulus for blood-feeding," Miller said. "Dr. Leal and co-workers escaped the key stimulus over-simplification to show that mosquito responses -- like our own -- result from a balancing of various positive and negative factors, all impinging on a tiny brain more capable than most people think of sophisticated decision-making."

Miller added that the UC Davis research shows that recent work on DEET mode-of-action, published in the journal Science, apparently was "flat-out wrong."

"One of the great attributes of science is that, over time, it is self-correcting," he said.

Mosquitoes detect DEET and other smells with their antennae. Leal and researcher Zain Syed discovered the exact neurons on the antennae that detect DEET (N,N-diethyl-3-methylbenzamide). These neurons are located beside other neurons that sense a chemical, 1-octen-3-ol, known to attract mosquitoes.

"I was so delighted when I first encountered the neuron that detects DEET, a synthetic compound," said Syed. "I couldn't believe my eyes because it goes against conventional wisdom. So I repeated the experiment over and over until we discussed the findings in the lab."

The UC Davis investigators set up odorless sugar-feeding stations, including some that contained DEET, and found that DEET actively repelled Culex quinquefasciatus mosquitoes, also known as Southern house mosquitoes. The mosquito transmits West Nile virus, St. Louis encephalitis, and lymphatic filariasis, a disease caused by threadlike parasitic worms.

"Despite the fact that DEET is the industry standard mosquito repellent, relatively little is known about how it actually works," said UC Davis research entomologist William Reisen. "Previous studies have suggested a 'masking' or 'binding' with host emanations. Understanding the mode of action is especially important because DEET is used as the standard against which all other tentative replacement repellents are compared."

Major Dhillon, president of the American Mosquito Control Association and district manager of the Northwest Mosquito and Vector Control District, Riverside, praised the UC Davis work as "a breakthrough."

"In the future, this new knowledge can be incorporated into developing new repellents and may be in control strategies for Culex quinquefasciatus and other mosquitoes," he said.

Research chemist Uli Bernier of the Mosquito and Fly Research Unit, USDA Agricultural Research Service, said the UC Davis study provides "an excellent explanation."

Bernier, who studies how repellents impact mosquitoes' feeding behavior, said the Leal-Syed work "presents as a very logical basis to help us understand how DEET is perceived by the mosquitoes, and this work provides an excellent explanation to link physiological processing within the mosquito to the (macroscopic) behavioral response that we observe in laboratory bioassays with this repellent."

Leal, a past president of the International Society of Chemical Ecology, received the 2007 Silverstein-Simeone Lecture Award for his innovative research on how insects detect smells and communicate within their species. He is former chair of the UC Davis Department of Entomology.