Skamania County Mosquito Control District

May 29, 2009

The Skamania County Mosquito Control District, through its association with the Northwest Mosquito and Vector Control Association, supports management of vector populations when and where necessary by means of an integrated program designed to benefit or to have minimal adverse effects on people, domestic animals, wildlife and the environment. This integrated pest management policy
recognizes that vector populations cannot always be eliminated, but often must be suppressed to tolerable levels for the well being of humans, domestic animals and wildlife, and that selection of scientifically sound suppression methods must be based upon consideration of what is ecologically and economically in the long-term interest of people.

An Integrated Pest management (IPM) plan is an effective, integrated strategy endorsed by the Department of Ecology and the Centers for Disease Control that emphasizes using multiple methods to achieve long-term control of mosquito populations before they become adults and are able to spread West Nile virus. Prevention is achieved through public education, surveillance, monitoring of treatment threshold levels, and control activities that use the least toxic and most environmentally friendly methods available.

Mosquito surveillance is an essential component of a comprehensive mosquito-borne disease prevention and control program. The objective of mosquito surveillance is to determine species composition, geographic distribution and abundance of potential vectors of mosquito-borne pathogens within each county by collecting and identifying larval and adult mosquitoes. Up-do-date information on mosquito species and their location is essential to developing effective prevention and control programs. Samples of adult female mosquitoes can also be analyzed for the presence of arboviruses, which help determine the primary vector species in an area.

An effective surveillance program includes: identifying and mapping breeding sites, identifying and mapping the location of potential vector species within each county through the collection of adult or larval mosquitoes; and testing of potential vector species for arboviruses, which for us, is done by the Washington State Department of Health, when laboratory capacity permits.

Benefits of Larval surveillance are used to determine the locations and seasons that mosquitoes use specific aquatic habitats and, when specimens are identified and counted, the information can be used to determine species composition and population densities. The information can be used to determine optimal times for application of larval control measures, including chemicals, biological controls, draining or impounding. It can also be used to help assess the effectiveness of both chemical and biological control measures. Routine larval surveillance data can be useful in interpreting adult mosquito surveillance data. For example, if larval surveys indicate 95-100 percent control by larvicides and yet the number of adults does not decline, one can suspect in the absence of reinfestation, that an important larval concentration was missed. A system for the detection of insecticide resistance is also provided through a larval surveillance program.

Adulticiding is the process of controlling mosquitoes when they are mature, flying mosquitoes. Adult female mosquitoes are the ones that bite, so ultimately they provide the largest threat to the public welfare. Adulticiding is necessary because larviciding is not 100% effective, some sites may be unknown and mosquitoes can migrate into the District from surrounding areas. Also, there are areas that we cannot treat and so mosquitoes have the opportunity to develop without interference from us. Adulticiding can provide temporary control of mosquitoes in a given area, but is not practical as the only method of control.

Adulticides We Use:

Pyrocide is an insecticide that contains pyrethrins. Pyrethrins are derived from the extract of chrysanthemum flowers. Pyrethrins are widely used for control of various insects. Pyrethrins are one of the least poisonous insecticides to mammals(1). Pyrethrins are low in toxicity to mammals because they are quickly broken down into inactive forms and pass from the body in the urine and feces (1,2). Pyrethrins have an extremely low pesticide movement rating because they bind tightly to the soil(1) and rapidly degrade in sunlight at the soil and in water.

AQUA-RESLIN® Mosquito Adulticide is highly effective, using permethrin and the synergist piperonyl butoxide (PBO). Utilizing our unique FFAST formulation, it’s one of the most advanced mosquito-fighting tools in the world.
FFAST is an acronym for Film-Forming Aqueous Spray Technology, and it allows water droplets to behave like oil. Water, however, eliminates the potential storage liability, environmental concerns, inconvenience and extra cost of oil sprays, while preserving their effectiveness.

(1) Ray, D.E. (1991). Pesticides derived from plants and other organisms. In W.J. Hayes Jr. & E.R. Laws (Eds.), Handbook of Pesticide Technology. Vol. 2. (pp.585-593). Toronto: Academic Press.
(2) Hayes, W. J. (1982). Pesticides Studied in Man. Baltimore: Williams & Wilkins.

Adulticiding Schedule:
Adulticiding, or what is commonly referred to as fogging, is a necessary aspect of an integrated mosquito management program. Adulticiding is used to reduce mosquito populations that have matured and are capable of flight (the larger percentage of Skamania County MCD’s program is larviciding, or controlling mosquitoes while in an immature stage in stagnant waters).
While adulticiding can be an effective tool and generally provides a certain level of control in a timely manner, it is susceptible to a number of factors. Wind speed (too high), temperatures (too cold or too hot), access (being able to physically drive to areas where the mosquitoes are located) and timing (maximizing mosquito exposure while minimizing exposure to people, pets, etc) are all considerations that can affect the performance of adulticiding. Consequently, these and other factors may prevent us from performing an adulticiding event on any given date/night and in the location that we have listed below.

All adulticiding in the District limits that fall into the Skamania County Mosquito Control District’s jurisdiction are listed below. Control efforts are often performed in non-populated areas to help reduce mosquito populations before reaching people. These sites are not updated on the website.

The vast majority of adulticiding will be conducted around sunset, during nighttime hours and/or possibly early morning (around sunrise).
Scheduled Date for Adulticiding: The week of June 1, 2009

• Adulticiding is scheduled for West end of District
North Bonneville:
• No adulticiding is scheduled
Home Valley:
• No adulticiding is scheduled