Mosquito Control

Physical Mosquito Control is the portion of our work which involves eliminating mosquito sources, improving access to these sources, or modifying sources to discourage mosquito breeding and encourage the growth of natural mosquito predators. The District staff spends much of its winter time maintaining existing drainage systems to assure that water flows freely to discourage mosquito breeding.

Other physical techniques that are used to reduce large mosquito breeding include making banks of holding ponds steeper to discourage emergent vegetation; removal of brush and berry bushes that provide cover to mosquito larvae, and construction and maintenance of roads that provide access to known mosquito sources that cannot be eliminated, such as isolations along the Sacramento River.

Another important aspect of physical control within the District involves source prevention. District staff reviews plans for large construction projects within the Shasta Mosquito and Vector Control District to be sure that they will not adversely affect natural runoff and create new mosquito sources. Cleaning up rubbish that may hold water, ditch maintenance, periodically changing bird-bath water, and cleaning rain gutters are all physical control measures that everyone can take around their homes to decrease the health risk and annoyance caused by mosquitoes.

Mosquito control is achieved in persistent water sources from ponds to watering troughs through the use of the mosquitofish, Gambusia affinis. This small relative of the guppy was originally discovered in The Gulf Coast area. Since its discovery in the 1920’s it has been released worldwide for mosquito control to the point that it is now the most widely distributed freshwater fish in the world. Shasta Mosquito and Vector Control District raises mosquito fish, which are given out free of charge to residents within the District for control of the mosquito’s aquatic life stages. Our integrated pest control methods also encourage natural mosquito control by discouraging growth of mosquito larvae while encouraging the survival and proliferation of natural mosquito predators. In addition, the District is always looking for ways to improve our biological control program.

Another aspect of our comprehensive, modern and integrated approach to mosquito control is chemical control. The Shasta Mosquito and Vector Control District uses a variety of environmentally compatible chemicals to control mosquito larvae and adults without causing harm to non-target organisms. Some of our products for larval control are based on unique bacteria, which produce protein substances that kill mosquito larva but are non-toxic to other insects and other animals. Insect growth regulators, which interrupt the mosquito’s life cycle, are also used. Other chemicals are applied which float on the surface of the water and prevent the mosquito larvae from obtaining air to breathe. Adult mosquitoes are killed using ultra-low-volume aerosol applications of modern pyrethrin-based chemicals. The District has five weather stations which are used to assure that application of chemicals to control adult mosquitoes takes place when conditions are right to get the maximum effectiveness against mosquitoes while having the least possible adverse effects on the environment. All of the mosquito control products used by the District are easily biodegradable and do not persist in the environment.