Question of the Week
Answer: There are several non-chemical options available. Commercial formulations of Bacillus thuringiensis var israelensis (also known as "Bti") are available in pellet or powder form that can be applied to rice paddy water. The Bti product is made up of the dormant spore form of this naturally occurring soil bacterium, as well as an associated pure toxin. The toxin disrupts the gut in the mosquito by binding to receptor cells present in insects, but not in mammals. Another form of Bti is available as a product called Mosquito Dunks. One donut-shaped dunk can control mosquito larvae in a volume of 100 square feet of water for 30 days. Please be aware that Bti is also lethal to a wide range of filter feeding insect larvae, including gnats.
Another option is to put "mosquito fish" (gambusia) into the rice paddy. These fish eat mosquito larvae. Several counties in California distribute mosquito fish at no charge to residents with man-made fishponds and pools as part of their Mosquito Abatement programs. However, it is not recommended to introduce them into natural habitats (streams, lakes, etc.), because these introduced species compete with native species.
A third option is to remove all the water periodically. Water in rice is primarily used as weed control, as the water drowns most weeds, which are not as efficient as rice is in transporting oxygen to the roots. Periodic removal of water will allow the paddy to dry out, killing the larvae, or at least reducing their populations.
See https://attra.ncat.org/attra-pub/biorationals/ for ATTRA's ecological pest management database and sourcing information for the above-mentioned biorationals.
Managing Mosquitoes on the Farm, UC Mosquito Research Program
This site has much information about managing mosquitoes in an agricultural setting, including rice paddies.
Pesticides and Public Health: Integrated Methods of Mosquito Management, Center for Disease Control
This article reviews various approaches to mosquito control, including biological.
Florida Mosquito Control Association
This site has links to dozens of other mosquito sites across the country, and abatement districts in both Florida and California.
The mention of specific brand names does not constitute an endorsement by NCAT, ATTRA, or USDA.
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