Objectives

Demonstrate the effects of water level in rice fields on 1) survival and development of mosquito (Culex tarsalis and Anopheles freeborni) larvae and 2) the interaction of mosquito larvae with invertebrate and vertebrate predators.

Summary of Results

No differences were found in mosquito larvae abundance among water depth treatments. However, mosquito larvae of both species developed slower in shallow water. The slower development could affect the adults and therefore influence larval control operations. Shallow water treatment also had a less diverse population of other organisms.

No differences were observed between weedy and weed controlled plots for larval abundance, larval development, or the diversity of organisms.

Project Leader: R. K. Washino, Department of Entomology, University of California, Davis.

Fish Species Compared for Mosquito Control

(Funded by the University of California)

Objectives

To determine whether juvenile Sacramento blackfish (Orthodon microlepidotus) could provide mosquito control comparable to the mosquito fish (Gambusia affinis) in experimental rice paddies. Also to determine if these two fish species in combination provided better mosquito control.

Summary of Results

Mosquito larvae numbers, mostly Anopheles freeborni, were significantly greater in paddies containing the Sacramento blackfish than in those containing mosquitofish. The paddies containing blackfish also tended to have more algae than other paddies. It does not appear worthwhile to mass rear the native Sacramento blackfish for mosquito control. Unlike mosquitofish, the juvenile blackfish cannot reproduce in the rice paddy habitat.

Project Leaders: Joseph J. Cech, Jr., Alison L. Linden, Stuart McAlister, and john C. Chiu, Department of Wildlife and Fisheries Biology, University of California, Davis.

Effectiveness of Fish Species and Aquatic Vegetation on Mosquito Abundance

(Funded by the University of California)

Objectives

The objectives are to determine the individual and interactive effects of mosquitofish, green sunfish, and aquatic vegetation on mosquito abundance.

Summary of Results

Mosquito fish (Gambusia affinis) and green sunfish (Lepomis cyanellus) both depressed populations of Anopheles freeborni mosquito. The green sunfish significantly reduced mosquitofish populations but despite this reduction, the two fish species together interacted to depress populations of A. freeborni even further than either species alone. The densities of A. freeborni were greater in rice paddies that contained southern naiad than in those containing rice.

Project Leaders: Rick Karban and Leon Blaustein, Department of Entomology, University of California, Davis.