Biological Control
What is biological control?
Biological control agents of mosquito larvae include predatory fish, predatory aquatic invertebrates, and mosquito pathogens.
Mosquitofish (Gambusia affinis)
Mosquitofish (Gambusia affinis) are used for larval mosquito control by the Alameda County Mosquito Abatement District for many reasons. They feed primarily at the water’s surface, where larvae can be found, and can tolerate a significant range in water temperature and water quality.
The District provides mosquitofish at no cost to Alameda County residents for mosquito control in water features, such as ornamental ponds, animal watering troughs, water gardens, fountains, and unmaintained swimming pools. The water in the pond must first be treated to remove chloramines (disinfectants present in tap water). Tap water conditioner products to remove chloramines can be purchased at pet stores.
It is against California Department of Fish and Game regulation for private citizens to plant mosquitofish in waters of the state without a permit (Title 14 CCR, Fish and Game Code, Section 1.63, Section 6400, and Section 238.5). Do NOT introduce mosquitofish to rivers, stock ponds, lakes, or creeks.
Request Mosquitofish for your Backyard Pond or other Water Features
To request mosquitofish for your water feature in Alameda County, please fill out our service request form to have mosquitofish delivered to your property. Mosquitofish can also picked up at our office Monday - Friday from 8am - 4pm (if possible, please bring a large container or bucket with water from the pond).
Before distribution, District staff must first determine if mosquitofish is the appropriate method to control mosquito larvae.
Information needed from Alameda County residents for mosquitofish:
- Contact information: Name, street address, phone number
- Size of water feature (gallons or square feet)
- Has the water been treated for chloramines?
- Tap water in Alameda County contain chloramines, which are toxic to mosquitofish and do not evaporate from water if left standing overnight. Water must be treated for chloramines (different than chlorine) before mosquitofish are added using a tap water conditioner or chloramine treatment kit. These are found at aquarium or pet supply stores.
Biorational products (also referred to as biological larvicides)
Mosquito pathogens include an assortment of viruses and bacteria. Examples of bacteria pathogenic to mosquitoes are
- Bacillus sphaericus (Bs)
- Bacillus thuringiensis israelensis (Bti), and
- Saccharopolyspora spinosa (spinosid).
These materials are also referred to as biorational products. Bs and Bti, produce proteins that are toxic to most mosquito larvae, while spinosid produces compounds known as spinosysns, which effectively control all larval mosquitoes. Bs can reproduce in natural settings for some time following release. Bti materials the District applies do not contain live organisms, but only spores made up of specific protein molecules. Both Bs and Bti are extremely mosquito specific and do not affect other aquatic life. All three bacteria are naturally occurring soil organisms that are commercially produced as mosquito larvicides.
