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June 6, 2006
Arroyo Chub May Prove Effective in Mosquito Control, UC Mosquito Research Program Study Suggests
DAVIS —Move over, mosquitofish. Make room for the arroyo chub. The arroyo chub, a native California fish, may prove a better choice than the non-native mosquitofish to control immature mosquito populations in sensitive watersheds and habitats, suggests research funded by the University of California Mosquito Research Program (UCMRP), UC Davis. Both eat mosquito larvae and pupae, thus reducing mosquito populations that can transmit such pathogens as the West Nile virus (WNV) and other arboviruses, said UC Riverside entomologist and principal investigator William Walton. The arroyo chub (Gila orcutti), he said, is a “good candidate to replace the mosquitofish (Gambusia affinis) as a biological control agent for mosquitoes in wetlands where non-native mosquitofish are undesirable; are perceived to pose a threat to native fauna; and where riverine conditions have a negative impact on mosquitofish populations.” Walton’s project is one of eight selected for UCMRP funding for the 2006-07 year. The principal investigators will share $260,000, to be distributed in August. Walton, launching a two-year project, “The Efficacy of a Native Biological Agent Against West Nile Vectors Inhabiting Constructed Treatment Wetlands,” said his earlier UCMRP-funded research with graduate student Alex Van Dam showed that the two fish species provided comparable levels of mosquito control. Both consume algae, insects and small crustaceans. However, the chub’s propensity to consume immature mosquitoes in vegetated, operational constructed treatment wetlands is unknown, the UC Riverside entomology professor said. Declining arroyo chub populations in the last 50 years make it a “native species of concern,” he said. The chub is native to the rivers and streams of southern California. specifically warm fluctuating streams. Unlike many native fish, however, the arroyo chub can withstand high water temperatures. The mosquitofish is not suitable for all environments, Walton said. “The hardiness, high reproductive potential, adaptability and other characteristics that make mosquitofish such a successful predator of mosquitoes in many different aquatic environments also make the mosquitofish an invasive species that has potentially serious negative effects on native fauna and ecosystems, especially in riverine systems in the southwestern United States.” “Release of mosquitofish into waters of the United States is greatly restricted,” said Walton. The other seven UCMRP-funded grants, director Lanzaro said, target mosquitoes that transmit WNV or the pesticides meant to kill them. Investigators are studying genetic transformation, mosquito pesticide resistance, effects of pesticides on other aquatic insects, and how crow roosts affect the risk of urban WNV transmission in California. The American crow is one of the main reservoirs for the virus, which is spread by female mosquitoes taking a blood meal. Aaron Brault, assistant professor, Department of Pathology, Microbiology and Immunology (PMI), UC Davis School of Veterinary Medicine, received funding for two grants, “ Temperature Regulation of Arbovirus Replication: Identification of Eurythermic Determinants of West Nile, St. Louis Encephalitis and Western Equine Encephalitis Viruses,” a new two-year proposal; and “Increased Diagnostic Capacity for the Detection of California Mosquito-Borne Viruses,” the third year of a three-year grant. Five other UC investigators received grants, all new proposals:
The UCMRP Grants Review Committee, comprised primarily of UC entomologists and mosquito abatement experts, recommends which projects should be funded. Lanzaro praised the partnership between the university and the mosquito abatement districts. “ California boasts the most technically advanced and efficient mosquito abatement program in the United States,” he said. “This success stems in large part from the effective partnership between state mosquito and vector control districts and research scientists on the various University of California campuses.” “The UC Mosquito Research Program provides funds to UC researchers who submit proposals aimed at finding solutions to problems faced by the abatement districts. The results of this partnership have provided California residents with a safer and healthier environment.”
Members of the grants review committee, co-chaired by Steve Mulligan, manager of the Consolidated Mosquito Abatement District, Selma, and Timothy Paine, professor of entomology at UC Riverside, are
Updated 2005 statistics just released by the California Department of Health show that WNV killed 19 people in 11 counties in 2005 and infected 935 in 40 counties. Five fatalities occurred in Riverside County; three in Kings County; two each in Fresno and San Bernardino counties; and one each in Amador, Butte, Madera, Sacramento, San Joaquin, Stanislaus and Tulare counties. In addition, state statistics show that 456 horses, 3,046 dead birds, 1,242 mosquito pools and 1,053 sentinel chickens tested positive for the virus last year. Birds most affected: American crows, Western scrub-jays, yellow-billed magpies and Stellar’s jays. First isolated in 1937 in the West Nile District of Uganda, WNV spread to New York in 1999 and reached California in 2002. Sacramento County, the nation’s 2005 “hot spot” for the virus, tallied 175 human illnesses and one death, according to the Centers for Disease Control and Prevention. UCMRP, headquartered at 396 Briggs Hall, UC Davis, is a statewide program established in 1972 by the UC Division of Agriculture and Natural Resources (ANR). Further information is available on the UCMRP Web site at www.ucmrp.ucdavis.edu or by contacting administrative assistant Nancy Dullum at (530) 752-6983 or at nadullum[at]ucdavis.edu. |
