Institute for Integrative Genome Biology


William WaltonWilliam E. Walton

Professor of Entomology;
Department Vice Chair

Mailing Address:

Entomology Research Museum /206
University of California
Riverside, CA 92521

Phone: 951-827-3919
Fax: 951-827-3086
Email: william.walton@ucr.edu

Lab Website


PhD 1986 University of Maryland, College Park
MS 1982 University of Maryland, College Park
BS 1978 University of Rhode Island

College/Division Affiliation:

College of Natural and Agricultural Sciences

Center/Inst Affiliation(s):

Center for Disease Vector Research
Center for Conservation Biology

Areas Of Expertise:

Mosquito Ecology

Awards / Honors:

1992-1994 - Who's Who in Science and Engineering

Research Summary:

I am an aquatic entomologist and ecologist who works mostly in natural and man-made wetlands.  Currently, the research in my laboratory has two foci related to disease-vector research: wetlands ecology with an emphasis on mosquitoes and bacteria used as an environmentally friendly method for controlling mosquitoes. 

The major emphasis of the wetlands research in my laboratory group is to integrate studies of mosquito biology and ecology with the design of control methodologies for pestiferous and pathogen-transmitting mosquitoes in wetlands.  We have been studying the effects of design features and management strategies for multipurpose constructed treatment wetlands on mosquito production and water quality performance.  In addition to studying the relationship of nutrients and other water quality variables to mosquito populations, our studies have focused across the food web from the temporal and spatial dynamics of bacterial populations to studies on alternative larvivorous fishes to the mosquitofish.  Our applied research on mosquito control in man-made wetlands has been complemented with basic research on the population dynamics of larval mosquito populations, the ecological stoichiometry of mosquitoes, the interaction of mosquitoes with natural enemies, and the influence of vegetation on the temporal and spatial distribution of mosquito larvae in wetlands.

A second research emphasis in my laboratory is the evolution of resistance to bacterial larvicides and the ecological consequences of evolved resistance.  Bacterial larvicides are perhaps the most promising method of environmentally friendly mosquito control currently available, particularly in treatment wetlands.  Two Bacillus are currently used for mosquito control in California; Bacillus sphaericus is comparatively more effective than is Bacillus thuringiensis subsp. israelensis (Bti) against mosquitoes inhabiting the organically enriched waters of most treatment wetlands.  Unlike Bti which contains multiple toxins that limit the potential for the rapid evolution of resistance in mosquitoes, the two toxin precursors in B. sphaericus act as a single toxin following ingestion and partial digestion by mosquito larvae.  Mosquitoes can evolve resistance to the B. sphaericus toxin very rapidly (>10,000-fold in 7-8 generations).  This finding takes on added significance for mosquito control in treatment wetlands of southern California because our studies of mosquito dispersal demonstrated that there is little potential gene exchange among populations of the predominant mosquito occurring at thickly vegetated wetlands.  Consequently, there is a greatly reduced potential for a resistant population to exchange genes with a nearby population that is susceptible to B. sphaericus.

We have been collaborating with Dr. Brian Federici and his laboratory on an NIH-funded project studying the development, modes of action and spectra of resistance/cross-resistance of transgenic strains of Bacillus that have been engineered for both increased efficacy against mosquitoes and a reduced potential for the evolution of resistance in the target mosquito populations.  Dr. Margaret Wirth coordinates this work in my laboratory and, in addition to her considerable expertise in studies of insect resistance, oversees the maintenance of 22 colonies of mosquitoes that have been selected for resistance to various Bacillus toxins and insecticides.  We also have collaborated recently on related projects with colleagues at the Pasteur Institute in Paris, Ohio State University, Cardiff University and Ben-Gurion University of the Negev.  The findings of these studies have important implications for genetic engineering of bacterial larvicides and resistance management in programs using bacterial larvicides as an environmentally-friendly approach to mosquito control.

Figure 1
Figure 2

Selected Publications:

List of publications from PubMed and Personal Website 

Lab Personnel:

Wirth, Margaret
Staff Research Associate —   
Popko, David
Graduate Student Researcher — 
Thieme, Jennifer
Laboratory Helper —
Beasley, Donald
Graduate Student Researcher —
Duguma, Dagne
Graduate Student Researcher —;
Henke, Adena
Graduate Student Researcher — 
Why, Jennifer
Graduate Student Researcher —

More Information

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Career OpportunitiesUCR Libraries
Campus StatusDirections to UCR

Genomics Information

Institute of Integrative Genome Biology
2150 Batchelor Hall

Tel: (951) 827-7177
E-mail: Aurelia Espinoza, Managing Director