- Author: Kathy Keatley Garvey
That quote sound familiar? Chemical ecologist Jacques Le Magnen (1916-2002) said that back in 1970.
World-renowned organic chemist Wittko Francke (right) of the University of Hamburg, Germany, called attention to Le Magnen's quote at a UC Davis Department of Entomology seminar on Wednesday noon, Dec. 8.
It bears repeating: "Nature is more a world of scents than a source of noise."
Insects communicate in a chemical language or chemical signals, Francke told the crowd.
Indeed, scientists have long known that methods that can attract or repel insects have important applications for agricultural pests and medical entomology.
Francke told how a queen bee secretes compounds that regulate development and behavior of the colony, and how an orchid releases the scent of a female wasp to attract male wasps— a scent that results in pollination. He also touched on the “calling cards” of a number of other insects, including bumble bees, wasps, pea gall midges, stingless bees, bark beetles and leafminers. He pointed out that that plants, too, send chemical signals.
UC Davis graduate students James Harwood and Amy Morice of the James R. Carey lab video-taped the seminar. It will be online soon at http://entomology.ucdavis.edu/news/webcastlinks.html
Francke was introduced by chemical ecologist-forest entomologist (and UC Davis Department of Entomology affiliate) Steve Seybold of the USDA Forest Service, Pacific Southwest Research Station, Davis.
No stranger to UC Davis, Francke previously collaborated with chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology, on attractants for navel orangeworm.
In his talk, Francke mentioned Leal’s discovery of a sophisticated mechanism for the isolation of the chemical communication channels of two species of scarab beetles.
Seybold and Francke are collaborating on the chemical signals of the walnut twig beetle, which in association with a newly described fungus, causes thousand cankers disease, a killer of walnut trees.
Thousand cankers disease (TCD) is now found in seven western states, plus Tennessee. Seybold is a key researcher in California.
Scientists believe that TCD occurs only on walnut, predominantly native black walnut, Juglans californica and J. hindsii, although the disease has been recorded on 10 species of walnuts or their hybrids in California.
Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, said Seybold, who has been studying the chemical ecology and behavior of bark beetles for more than 25 years. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus.
A USDA/UC Davis research team is tracking the pathogen and the beetle throughout California, particularly in commercial orchards.
That all points back to “Nature is more a world of scents than a source of noise.”
- Author: Kathy Keatley Garvey
Walnuts are packed with vitamins, minerals and antioxidants, right?
Right.
And sometimes a little protein.
Protein, as in larvae. That's not a welcome sight.
Sometimes you'll find two or three navel orangeworm (NOW) larvae inside a single walnut, along with copious amounts of webbing and frass.
We once stored a bucket of untreated walnuts inside a vacant outbuilding. By spring, we had larvae crawling up the walls and moths trying to find an opening and us trying to find our sanity.
Last weekend I went on The Great Navel Orangeworm Search. I collected three walnuts that had fallen onto the sidewalk. Two of the walnuts were perfect. Drats!
Ah, but when I cracked open the third, I spotted the larvae.
Three larvae inside the third walnut on the third of January at 3 o'clock in the afternoon.
UC Davis entomology professor Frank Zalom said the best way to tell if the larvae are navel orangeworm is "to check for the presence of a crescent-shaped marking on the sides of the second segment behind the head."
The larva of the codling moth doesn't have this marking.
NOW is no friend of walnut growers. The moths deposit their eggs inside the mummy nuts--the ones left on the trees after a harvest--or the fallen nuts. Next season: more trouble. Economic trouble.
A pest of both fruits and nuts, NOW was first found in navel oranges; thus the name.
As for the three larvae I found inside the walnut, as soon as I split the hull, they were off and running.
Or rather, off and crawling.
- 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.
