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| World-renowned organic chemist Wittko Francke met with UC Davis researchers following his presentation on Wednesday, Dec. 8 at a UC Davis Department of Entomology seminar. From left are chemical ecologist Zain Syed of the Walter Leal lab; chemical ecologist and forest entomologist Steve Seybold of the USDA Forest Service, Pacific Southwest Research Station, Davis, and an affiliate of the UC Davis Department of Entomology; Wittko Francke; and chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology. (Photo by Kathy Keatley Garvey) |
DAVIS--“Nature is more a world of scents than a source of noise,” world-renowned organic chemist Wittko Francke of the University of Hamburg, Germany, told the UC Davis Department of Entomology seminar held Wednesday, Dec. 8 in Briggs Hall.
He was quoting pioneer olfaction-taste researcher Jacques Le Magnen (1916-2002).
Insects communicate in a chemical language or chemical signals, Francke said.
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—activities that result 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, and noted that plants, too, send chemical signals.
UC Davis graduate students James Harwood and Amy Morice of the James R. Carey lab webcast the seminar. It is posted online.
Francke was introduced by chemical ecologist and forest entomologist Steve Seybold, of the USDA Forest Service, Pacific Southwest Research Station, Davis, and a faculty affiliate of the UC Davis Department of Entomology.
No stranger to UC Davis, Francke has 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, an emerging threat to walnut trees in the United States. Trees in the Davis area are among the victims.
Thousand cankers disease is now found in eight western states (Arizona, California, Colorado, Idaho, New Mexico, Oregon, Utah and Washington), plus Tennessee. Seybold’s research group has led the effort to characterize the disease in California. The walnut twig beetle is Pityopthorus juglandis and the newly described fungus is Geosmithia morbida.
Scientists believe that the disease 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 the disease 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.
--Kathy Keatley Garvey
Communications specialist
UC Davis Department of Entomology
(530) 754-6894
