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Medflies: Permanent Residents
The Mediterranean fruit fly, considered the world's worst agricultural pest, is one of at least five fruit flies established in California. It cannot be eradicated.
So says entomologist James Carey of the UC Davis Department of Entomology and Nematology, who has been dogging medflies since his faculty appointment in 1980. (See what drove him.)
Carey and UC Davis-affiliated colleagues Nikos Papadopoulos and Richard Plant wrote the eye-opening research piece, "From Trickle to Flood: The Large Scale, Cryptic Invasion of California by Tropical Fruit Flies" in the current edition of the renowned Proceedings of the Royal Society B.
Their work "clearly demonstrates that at least five and as many as nine species of tropical fruit flies, including the infamous Medfly, are permanently established in California and inexorably spreading, despite more than 30 years of intervention and nearly 300 state-sponsored eradication programs aimed at the flies," wrote Pat Bailey in a UC Davis News Service story released today.
The findings, Bailey pointed out, have "significant implications for how government agencies develop policies to successfully manage pests that pose a threat to California's $43.5 billion agricultural industry."
Carey, an international authority on fruit-fly invasion biology, told her that "Despite due diligence, quick responses, and massive expenditures to prevent entry and establishment of these insects, virtually all of the fruit-fly species targeted by eradication projects have been reappearing in the same locations — several of them annually — and gradually spreading in the state."
Carey, Papadopoulos and Plant detailed the problem in the opening paragraph of their meticulously researched paper: "Since 1954 when the first tropical tephritid fruitfly was detected in California, a total of 17 species in four genera and 11,386 individuals (adults/larvae) have been detected in the state at more than 3348 locations in 330 cities." That's three out of four California cities.
Michael Parrella, professor and chair of the UC Davis Department of Entomology and Nematology: "The study has dramatic implications for California agriculture and the state’s international trading partners, and speaks to the urgent need to alter current eradication policies aimed at invasive species."
Frank Zalom, UC Davis entomology professor and incoming president of the 6500-member Entomological Society of America: “This study deserves serious consideration, and I hope that it helps lead to new discussions on a long-term approach for dealing with fruit flies and similar exotic pests by the United States and international regulatory authorities."
Former UC Davis chancellor Ted Hullar (1987-1994), one of the first to believe in "the science" that Carey presented, said: “From our first conversation, Jim struck me as a serious-minded guy, with strong ideas and clear focus, pursuing his insights and beliefs no matter the struggle. Good science and progress comes from that, making new paths in tough terrain, believing in the power of journey, as well as goal.”
The Medfly prefers such thin-skinned hosts as peach, nectarine, apricot, avocado, grapefruit, orange, and cherry. The female may lay one to 10 eggs per fruit or as many as 22 eggs per day. She may lay up to 800 eggs during her lifetime, but usually about 300.
We remember when the Medfly wreaked economic havoc in the Solano County city of Dixon in September 2007. We were there.
At the time, Carey told us that "this may be just one of many isolated pockets of medfly infestations in California. This is really serious because the invasion process is so insidious."
The Medfly has been multiplying and spreading undetected--like cancer--for years, he said. "It may be a symptom of a much larger problem. But any way you look at it, this is the first really big outbreak in the Central Valley."
CDFA set up a command center at the Dixon May Fair and imposed a 114-mile radius quarantine of fruits, vegetables and nuts. Dixon was deep in the throes of tomato and walnut harvesting. The owner of a 65-acre organic produce farm that ships to 800 clients worried that he might lose $10,000 a week in potential sales.
Among the actions that the California Department of Food and Agriculture (CDFA) took at the onset:
- Stripped all fruit from trees within a 100-meter radius of all Medfly finds
- Ground-sprayed the organic compound Naturalyte (the active ingredient is Spinosad, a naturally occurring product of a soil bacteria) within a 200-meter radius of all Medfly finds
- Set 1,700 fruit fly traps within an 81-square mile grid in all of Dixon and the surrounding area from near the Yolo County border to Midway Road
- Began aerially releasing 1.5 million sterile male medflies (dyed pink for easy detection) over a 12-square mile area on Sept. 14, with weekly releases of 3 million medflies scheduled for at least nine months
- Set up a yearlong command center, with four portable buildings and a task force of 25, on the Dixon May Fair grounds
Fast forward to today. Now that the Medfly has been declared a "permanent resident," what's next?
Carey agrees that “CDFA needs to continue to respond to outbreaks as they occur, but he advocates long-term planning based on “the science” that the insects are established. This includes heightened monitoring levels for the agriculturally rich Central Valley, an economic impact study, risk management/crop insurance, cropping strategies, fly fee zones/post harvest treatments, emergency/crisis planning, genetic analysis and a National Fruit Fly Program.
“Inasmuch as the Mediterranean, Mexican, Oriental, melon, guava and peach fruit flies have all been detected in the Central Valley, monitoring this incredibly important agricultural region should be increased by 5 to 10-fold in order to intervene and suppress populations and thus slow the spread,” Carey says.
“These pests cannot be wished away or legislated out of existence. Policymakers need to come to grips with this sobering reality of multiple species permanently established in our state in order to come up with a long-term, science-based policy for protecting agriculture in our state.”
(See James Carey's website for links to his work on fruit fly invasion.)
Mediterranean Fruit Fly. (Photo by Jack Kelly Clark)
Fruit Fly Research: Link to Human Sleep Disorders
If you're suffering from a sleep disorder, then you'll want to know the kind of research that molecular geneticist Joanna Chiu of the UC Davis Department of Entomology is doing--with fruit flies.
The research may one day lead to alleviating your sleep disorder.
Chiu and two of her former colleagues at Rutgers just published groundbreaking research in the journal Cell. They identified a new mechanism that slows down or speeds up the internal clock of fruit flies.
By mutating one amino acid in a single protein, "we changed the speed of the internal clock and flies now ‘think' it is 16 hours a day instead of 24 hours a day," said Chiu, an assistant professor of entomology.
"Our goal, of course, is not to trick flies into thinking the day is shorter or longer, but to dissect this complex phospho-circuit (phosphorylation sites) that controls clock speed in metazoans."
Their work, involving the fruit fly, Drosophila melanogaster, was funded by the National Institutes of Health.
The world of circadian clocks is a complex one. "Living organisms-plants, animals and even bacteria-have an internal clock or timer that helps them to determine the time of day," Chiu said. "This internal clock is vital to their survival since it allows them to synchronize their activity to the natural environment, so that they can perform necessary tasks at biologically advantageous times of day."
"A functional clock is required to generate proper circadian rhythms of physiology and behavior including the sleep-wake cycle, daily hormonal variations and mating rhythms," Chiu said.
Read more about her research on the UC Davis Department of Entomology website.
The fruit fly, small in size--about 1/8th inch long--stands tall as a prized tool for genetic research and developmental studies.
Indeed, the red-eyed fly is a "golden bug.”
Molecular geneticist Joanna Chiu at work in her lab at UC Davis. (Photo by Kathy Keatley Garvey)
In the Thick of Fruit Flies
Roger Vargas is in the thick of fruit-fly research and he probably wishes those insects would thin out.
He's a research entomologist at the USDA-ARS Pacific Basin Agricultural Research Center in Hilo, Hawaii. For those who don't deal with acronyms, that's the Agricultural Research Service of the U.S. Department of Agriculture.
Vargas' key research interests include mass rearing, sterile insect technique, ecology, biological control, and area-wide integrated pest management (IPM) of fruit flies.
Vargas will be at the University of California, Davis, on Wednesday, Feb. 9 to speak on "Area-Wide Fruit Fly Programs against Fruit Flies in Hawaii, French Polynesia and California." His talk, sponsored by the UC Davis Department of Entomology and part of its winter seminar series, is set from 12:10 to 1 p.m. in 1022 Life Sciences Addition, corner of Hutchison and Kleiber Hall drives.
The lecture will be webcast live at http://uc-d.na4.acrobat.com/ucsn1/ and then archived here. He plans to cover current area-wide management programs against Bactrocera fruit flies in Hawaii, French Polynesia, and California.
"Fruit flies (Diptera: Tephritidae) are among the most economically important pests attacking soft fruits worldwide," Vargas says. "Bactrocera is a tephritid fly genus of at least 440 species distributed primarily in tropical Asia, the south Pacific, and Australia. However, these species have been spreading throughout the world at an alarming rate over the past 15 years.
"Oriental fruit fly (B. dorsalis) has become established and is spreading throughout French Polynesia.
"Carambola fruit fly (B. carambolae) is established and spreading throughout areas of South America.
"B. invadens, B. latifrons and melon fly (B. cucurbitae) are established and spreading in Africa.
"The peach fruit fly (B. zonata) is established and spreading in Africa and the Mediterranean region."
In fact, Vargas says, every year Bactrocera species are accidentally introduced from various parts of the world into California, requiring expensive treatment programs.
For an up-close and personal look at a fruit fly, check out the USDA-ARS photo of a Oriental fruit fly laying eggs in a papaya (below).
Coming soon...to a fruit near you...
Roger Vargas
Fruit Fly
Not a Failure to Communicate
The female silkworm moth releases a sex pheromone, bombykol, that's very enticing to the male. He can detect it from miles away.
Now researchers in the UC Davis Department of Entomology have discovered that the fruit fly has a native odorant receptor that detects the silkworm moth’s sex pheromone, and that it’s “amazingly more sensitive” than the moth’s odorant receptor.
Their work could open research doors for insect-inspired biosensors.
Walter Leal, professor of entomology, and postdoctoral scholar Zain Syed know the olfactory systems of silkworm moths (Bombyx mori) and fruit flies (Drosophilia melanogaster) well.
In a serendipitous discovery, the chemical ecologists found that the fruit fly’s odor detector not only detects bombykol, but responds to bombykol with high sensitivity. Their groundbreaking research, Bombykol Receptors in the Silkworm Moth and the Fruit Fly, was published May 3 in the Proceedings of the National Academy of Science (PNAS).Their research follows on the heels of another study they published in PNAS in 2006 with the Deborah Kimbrell genetics lab in the UC Davis College of Biological Sciences. Bottom line: they found that genetically engineered fruit flies responded to the silkworm moth scent of a female.
Now Leal and Syed have identified the odorant receptor in the male fruit fly that detects the sex pheromone.
Ecologist and evolutionary biologist Fred Gould of North Carolina State University, not affiliated with the research, says the work of the UC Davis researchers "provides important guidance and tools for other researchers who want to explore the pheromone communication systems of other species, or who want to further dissect the mechanisms within the specialized hairs of silkworms that enable this high sensitivity.”What we have here with the silkworm moths and fruit flies is definitely not a "failure to communicate."
Mulberry Tree
Drosophila Head
Scent of a Female
