West Nile Virus Larvicide Questions and Answers

What is larviciding? become sluggish and die within 24 hours is Larviciding is the use of pesticides to applied to standing water in a granular form. control specific species of insects such as This agent is used to control mosquito larvae mosquitoes. Larvicides kill the larvae before in temporary standing water. Standing water it becomes an adult mosquito. Controlling is water that remains in an area for more mosquitoes when they are in the water is an than one week (seven days or more) and is effective approach because the mosquito is not flowing or subject to wind or wave somewhat isolated and known breeding sites action. Standing water can collect on the can be recorded and routinely monitored. ground, a roof, pool covers, and in For many districts, this is the bulk of their containers such as tires and eaves. operations. Are there any risks to using this Why is larvicide being used? product (Bti)? Larvicide is used in areas where monitoring Bacillus thuringiensis israelensis (Bti) has information shows that mosquito larvae are no short or long term health effects on present. Larvicide is only applied when humans or on wildlife, including aquatic other measures for the reduction and control organisms. Bti is only used on temporary of breeding sites do not work to minimize standing water (ditches, etc.) and on the risk of West Nile virus. For Kittitas temporary or permanent no-flowing water County we chose to larvicide a specific area sites. It represents a very low risk to other because a positive equine was recorded last non-target insect species. year in Upper County. How is the West Nile virus program What products are being used? carried out? There are a number of different products The Kittitas County Health Department’s available for abatement practices. Often West Nile virus program is focusing on times, one product will be better suited for a three areas this year: particular situation than another product. The larvicide that has been selected for • Public education mosquito control in Kittitas County is Bti • Monitoring and surveillance (Bacillus thuringiensis israelensis). • Larviciding If standing water can be removed to Bacillus thuringiensis israelensis, known as eliminate the potential mosquito breeding Bti, is a bacterium. Bti contains protein site, this is done. In this case, larviciding is crystals that rupture digestive cells in not necessary. If the standing water cannot mosquito larvae when ingested and larvae be removed (as in catch basins, ditches,

507 N. Nanum St. Suite. 102 · Ellensburg, WA 98926 T: 509.962.7515 · F: 509.962.7581

ponds, etc.), these areas are monitored for instructions for use must be strictly followed the presence of mosquito larvae. Larvicide is at all times. This larvicide cannot be applied applied only when mosquito larvae are to catch basins or other waters that can drain found. The larvicide that would like to be off your property. used in Kittitas County is in granular form. Larvicide is not sprayed into the air or onto Are there any other ways to control surrounding land. mosquitoes that don’t include the . use of pesticides? How do you investigate possible There are several ways to control breeding sites? How do you know if mosquitoes other than by the use of there are mosquitoes breeding in this pesticides. You can remove all potential site? places where mosquitoes might breed. This The definition used for standing water is includes items around the yard such as old water that persists for seven days or more. If tires and containers where water might the site meets the definition for standing collect. Also, fill in low areas and ditches water the site will be investigated. The that can collect water. Elimination of investigation includes dipping of the water mosquito breeding sites is an effective to determine if mosquito larvae are present. measure of control although it may not be feasible in all cases. What larvicide can I use on my property? Will I be kept informed? There is a larvicide product containing Bti The Kittitas County Health Department uses that received federal approval in 2003 and is a variety of methods to keep the public available at local stores. This larvicide informed about West Nile virus. Methods product can only be used for the treatment of include periodic media releases, the Health standing water sites on your own property. Department’s website, and the distribution of information at locations throughout the The product is available at many hardware county. stores. Please Note - The manufacturer’s

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Kittitas County Public Health Department 507 N Nanum St. Suite 102 Phone: 509-963-7515 Fax: 509-962-7581

507 N. Nanum St. Suite. 102 · Ellensburg, WA 98926 T: 509.962.7515 · F: 509.962.7581