- Author: Kathy Keatley Garvey
Chemical ecologists at the University of California, Davis, are changing their navel-orangeworm research direction after an elementary school student’s science project found that the major agricultural pest prefers pistachios over almonds and walnuts.
Gabriel Leal, 11, a sixth grader at Willet Elementary School, Davis, prefers pistachios over all other nuts so he figured that the navel orangeworm (NOW) would, too.
“Pistachios taste better,” reasoned Gabriel, whose family says he can eat an entire bag of pistachios at one sitting. Pistachios have long been his favorite nut, so why wouldn’t the navel orangeworm prefer pistachios over almonds and walnuts, too?
Why not?
So the sixth grader hypothesized that the insect would lay more eggs in pistachios than in almonds and walnuts, contrary to widely published research that indicates an almond preference.
“Everybody knows that navel orangeworms prefer almonds,” said his father, Walter Leal, a chemical ecologist and professor of entomology at UC Davis. Research published recently in the California Agriculture journal also indicates the preference.
“But in science,” Leal said, “we should believe what we see, not what others tell us. I know that Gabriel prefers pistachios, but I assumed the navel orangeworm’s taste receptors were different.”
Wrong. Gabriel’s research showed that the insects preferred pistachios, just like him.
The findings led to a report at the Almond Board of California’s 32nd Almond Industry Conference, held Dec. 1-2 in Modesto, and launched a new direction of navel orangeworm chemical ecology research at UC Davis
Gabriel performed his research in his father’s UC Davis lab, under the volunteer supervision and mentoring of chemical ecologist Zain Syed.
“It was a ‘choice’ experiment where Gabriel placed mated and gravid (egg-filled) females in a cage,” Syed said. “He used four commercially available navel orangeworm traps (Ovitraps). One trap was filled with 50 grams of shelled pistachios, another with 50 grams of almonds, and the third with 50 grams of walnuts. The empty trap served as the control to check if the trap itself had any effects on attracting egg-laying moths. The eggs laid in the ovitraps were counted for two consecutive nights.”
Said Leal: "Gabriel got enough replicates to demonstrate that female orange navelworms do prefer pistachios over walnuts and almonds. We are very excited with our little scientist’s discovery. I reported ‘our’ findings at the state almond industry conference in Modesto. And these findings changed our research direction, because we are now interested in determining what chemistry in pistachios attracts female navel orangeworms.”
“Oviposition (egg-laying) attractants derived from almond oil are used to monitor female populations in the field,” Leal explained, “but during hull split, the chemical from the natural source (crop) competes with the synthetic material in traps. If we use pistachio-derived attractants in the almond field there will be no competition throughout the flight season.”
So how significant a pest is the navel orangeworm?
According to research entomologist Brian Higbee of Paramount Farming, Bakersfield, "it is the primary and most destructive pest on almonds and pistachios." California has some 152,000 acres planted in pistachios, while the state's almond acreage totals more than 700,000.
"The economic impact of NOW damage varies from year to year, but it can easily reach $10-15 million for our company and much higher statewide," Higbee said.
The take-home message? "Well, in science we should never underestimate anyone's idea,” Leal said. “That's why the academic environment is so enriching: students come with new ideas, but I never imagined we would benefit so much from a science project for elementary school."
For more, see news story on the UC Davis Department of Entomology Web site.
- Author: Kathy Keatley Garvey
When UC Davis chemical ecologist Walter Leal received a major award from the Entomological Society of America at its 56th annual meeting, held in Reno, DEET has something to do with it.
Leal, who received the Recognition Award in Insect Physiology, Biochemistry and Toxicology from ESA president Michael Gray, has amassed an amazing record of productivity. Most recently: his lab discovered the mode of action for the mosquito repellent, DEET.
Contrary to previous hypotheses, DEET doesn't jam a mosquto's sense of smell or mask the smell of the host. The reason why mosquitoes avoid DEET is they don't like the smell and avoid it.
Leal, professor of entomology and former chair of the UC Davis Department of Entomology, was one of seven professionals receiving distinguished awards at the ESA meeting. The other categories were extension, entomology, horticultural entomology, teaching, the certification program, and early career innovation.
A pioneer in the field of insect olfaction, Leal is best known for his research on the mode of action of odorant–binding proteins and odorant-degrading enzymes on the identification and synthesis of insect sex pheromones and on insect chemical communication.
As colleague Ring Cardé, chair of the Department of Entomology at UC Riverside, said: "Dr. Leal is one of the leading scientists worldwide studying the chemistry of pheromone communication in insects and related arthropods.”
- Author: Kathy Keatley Garvey
When the Entomological Society of America's 56th annual meeting takes place Nov. 16-19 in Reno, UC Davis entomologists will be out in force.
And they'll be highly honored.
Entomology professors Michael Parrella and Frank Zalom will be inducted as Fellows, which means they are among the top insect scientists in the world. The 5700-member ESA, formed in 1889, is a non-profit organization that includes representatives from educational institutions, government, health agencies, and private industry.
As Lynn Kimsey, chair of the UC Davis Department of Entomology and director of the Bohart Museum of Entomology said: “These are highly prestigious awards, granted only to 10 or fewer entomologists every year. Michael Parrella and Frank Zalom are carrying on our department’s tradition of excellence and commitment."
Eight other UC Davis entomologists have received the honor since 1947.Richard M. Bohart (1917-2007), for whom the Bohart Museum of Entomology is named, was the first UC Davis entomologist to be selected an ESA Fellow (1947). Seven others followed: Donald McLean, 1990; Harry H. Laidlaw Jr. (1907-2003), 1991; John Edman, 1994; Robert Washino, 1996; Bruce Eldridge, 2001; William Reisen, 2003 and Harry Kaya, 2007.
Parrella is the associate dean of the Division of Agricultural Sciences, College of Agricultural and Environmental Sciences, and former chair of the UC Davis Department of Entomology. Zalom is a former director of the UC Integrated Pest Management Program and the former vice chair of the department. Zalom also was nominated for ESA president recently by the ESA's Pacific Branch.
You can read about their many accomplishments here.
Both entomologists will be honored by their peers on Sunday night, Nov. 16 at the ESA's plenary session in the Reno-Sparks Convention Center.
Zalom also will be honored as part of the UC's seven-member Almond Pest Management Alliance IPM Team that will receive the Entomological Foundation’s 2008 Award for Excellence in IPM. Other members are Carolyn Pickel, UC Cooperative Extension, Sutter-Yuba counties; Walter Bentley, UC Kearney Agricultural Center, Parlier; UC Cooperative Extension farm advisors Mario Viveros, Kern County, Roger Duncan, Stanislaus County, and Joe Connell, Butte County; and scientist Barat Bisrabi, Dow AgroSciences. Both Pickel and Bentley are UC IPM advisors.
Another high honor at the same plenary session: UC Davis chemical ecologist Walter Leal will receive the ESA's coveted Recognition Award in Insect Physiology, Biochemistry and Toxicology for his innovative and creative research involving insect communication. His lab recently discovered the mode of action for the mosquito repellent, DEET.
Among other UC Davis folks to be honored during the conference:
Mosquito researcher Chris Barker, who received his doctorate earlier this year, is the winner of the John Henry Comstock Graduate Student Award from the Pacific Branch of the ESA.
Noted entomologists Maurine and Catherine Tauber, retired from Cornell and now affiliated with UC Davis, will be honored for their diverse entomological accomplishments at a special symposium. Lester E. Ehler, emeritus professor, will speak on their life's work. In addition, other faculty and graduate students will deliver presentations at the conference.
Congratulations to all! Very well deserved!
They are among the reasons why the Chronicle of Higher Education selected UC Davis the No. 1 entomology department in the country (November 2007).
- Author: Kathy Keatley Garvey
Whew, that stinks!
If you've ever smelled a mosquito gravid trap, you know it's not heaven-scent. This isn't about the aroma of summer roses or the whiff of freshly baked cinnamon rolls or the fragrance of vanilla-laced skin cream.
No. This is something that stinks to high heaven. Probably low heaven, too.
It's s-o-o bad (how b-a-d is it?) that you just want to distance yourself from the stench: you hold your nose, mutter “P.U.” and make like a Lightening Bolt (Olympic gold-medal sprinter Usain Bolt).
Said UC Davis chemical ecologist Walter Leal: “It smells like a latrine."
So he and his researchers set out to find a synthetic mixture that attracts mosquitoes but is odorless to humans. And they have. Their mixture, containing the compounds trimethylamine and nonanal in low doses, lures Culex mosquitoes just as effectively as the current gravid trap attractants. But look, ma, no smell!
They did it with what Leal calls "reverse chemical ecology."
The results are published in the current edition of the Public Library of Science Journal or PLOS One.
This research could play a key role in surveillance and control programs for Culex species, which transmit such diseases as West Nile virus, encephalitis and lymphatic filariasis.
What are gravid traps? They're chemical- and water-infused traps, sometimes called oviposition traps or ovitraps. They're meant to attract blood-fed mosquitoes searching for places to lay their eggs. Scientists monitor these traps to determine the presence of West Nile-infected mosquitoes.
“The gravid traps are more important (than carbon-dioxide traps) for surveillance,” Leal said, “as they capture mosquitoes that have had a blood meal and thus, more opportunity to become infected.”
Leal said that another advantage of the gravid traps is that with the capture of one female mosquito, that eliminates not only her, but hundreds of her would-be offspring. “Each female mosquito has the potential to produce about 200 eggs, and she can have as many as five cycles. So when we capture a gravid mosquito, that can remove as many as 500 females.”
Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)The compounds used in the research, Leal said, are “simple and inexpensive” and would be of great benefit “to not only us but third-world countries where Culex quinquefasciatus is a problem.” Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)The researchers did preliminary field testing in Davis and Sacramento but when aerial sprays mitigated the levels of West Nile virus-infested mosquitoes, they set up traps in Recife, Brazil, a city endemic for lymphatic filariasis. Leal is a native of Brazil.
Other scientists involved in the study included UC Davis researchers Wei Xu, Yuko Ishida, Zain Syed, Nicolas Latte, Angela Chen and Tania Morgan; associate professor Anthony Cornel, associate professor of entomology at UC Davis and director of the Mosquito Control Research Laboratory, based at the Kearney Agricultural Center, Parlier; and Rosângela M. R. Barbosa and André Furtado of the Department of Entomology, Centro de Pesquisas Ageu Magalhaes-Fiocruz, Recife, Brazil.
Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)(See more information on the UC Davis Department of Entomology Web site).
- Author: Kathy Keatley Garvey
We know it works, but how?
Just how does DEET work? Does it jam the senses of a mosquito? Does it mask the smell of the host?
You spray the chemical repellent on your arm and thankfully, those darn skeeters leave you alone. They need a blood meal to develop their eggs, so off they buzz to find another host, one that's not so inhospitable.
But why do mosquitoes avoid DEET?
Well, they avoid it because it smells bad to them. Yes, they can smell it--that's why they avoid it.
The groundbreaking research, the work of UC Davis chemical ecologist Walter Leal and researcher Zain Syed, is published today in the Proceedings of the National Academy of Sciences (PNAS), which lifted the news embargo at 2 p.m., Pacific Standard Time.
The research contradicts a Science article published in March by researchers at Rockefeller University, New York. The researchers, as other scientists have long believed, said mosquitoes can't smell DEET because it jams the odorant receptors in insect nervous systems.
The Leal-Syed research solidly establishes the real mode of action.
Noted entomologist James "Jim" Miller of Michigan State University praised the Leal-Syed work as correcting “long-standing erroneous dogma.”
Said Miller: "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. 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.”
“This new work corrects long-standing erroneous dogma, and shows that recent work on DEET mode-of-action published in the flagship journal, Science, apparently was flat-out wrong,” Miller said. “One of the great attributes of science is that, over time, it is self-correcting."
Leal, past president of the International Society of Chemical Ecology and former chair of the UC Davis Department of Entomology, said previous findings of other scientists showed a “false positive” resulting from the experimental design.
Now that we know that skeeters can smell it, this will no doubt lead to better methods of insect control. Or, as Major Dhillon, president of the American Mosquito Control Association and district manager of the Northwest Mosquito and Vector Control District, Riverside, said: ”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.”
Those darn female mosquitoes, always in a “Let-us-prey” mood, have clearly met their match: the "why" behind "Let us spray."
