Programmatic review of the mosquito control methods used in the highly industrialized rice agroecosystems of Sacramento and Yolo Counties, California

Abstract

In the Sacramento Valley (California, USA), rice (Oryza sativa L.) fields are an economically important crop and productive habitats for the mosquito species Culex tarsalis and Anopheles freeborni. Since 2010, approximately 150 km2 of conventional and 16 km2 of organic rice have been grown in Sacramento and Yolo Counties. These fields are often within mosquito flight-range of both rural towns and urban centers. Culex tarsalis are highly competent vectors of West Nile virus, and An. freeborni are aggressive, mammalophagic, nuisance biters. The Sacramento–Yolo Mosquito and Vector Control District provides mosquito control for the two counties in its jurisdiction. The principles of Integrated Pest Management are used to control mosquitoes in rice growing areas, relying upon a range of surveillance and control interventions. Larvae are controlled by limiting habitats that enable development of immature mosquitoes while balancing agricultural and wildlife needs, applying larvicides, and the use of Gambusia affinis (mosquitofish). Adult mosquitoes are controlled by ultra-low volume pesticide applications. The program was assessed for larval and adult mosquito control efficacy and areas of programmatic improvement identified. Because rice fields are productive habitats for mosquitoes, complete elimination of the habitat is not a feasible goal, thus efforts are aimed at interrupting disease transmission and reducing the number of mosquitoes that traverse into populated areas.