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.

For an update on where we will be fogging next please click here.

The pesticides being used for truck-mounted spraying are Anvil 10+10 and DeltaGard; the active ingredient for Anvil 10+10 is d-phenothrin (Sumithrin®).  The active ingredient for DeltaGard is Deltamethrin.   The product used in the airplane is Dibrom Concentrate, the active ingredient is naled. 

Anvil 10+10 and Dibrom are applied at less than one ounce per acre and DeltaGard (which is diluted with water at a 2:1 mixture (2 parts water to 1 part DeltaGard) is applied at two ounces per acre; which means the exposure level for people and animals in the spray block is extremely low.  At high concentrations the products could have detrimental effects, so the risk is higher for the applicators and loaders than it is for the general public.  We apply the pesticides according to the product label and calibrate our equipment regularly to ensure that we are using the products as safely and effectively as possible.

Adulticides We Use in Trucks:

Pyrethroids

A pyrethroid is a synthetic version of pyrethrin, which is a natural chemical found in chrysanthemum flowers.  Pyrethroids are the most common active ingredient in commercially available insect sprays and are also used as structural termiticides.  The pyrethroids permethrin, resmethrin, and sumithrin are registered for mosquito-control programs.  Benton County Mosquito Control presently uses a sumithrin based product called Anvil 10+10 (10% Sumithrin and 10% PBO).

This is the EPA's statement on Sumithrin for mosquito control:  Sumithrin (d-Phenothrin)

Piperonyl Butoxide (PBO)

Piperonyl butoxide is a synergist used in a wide variety of pesticides.  Synergists are chemicals that lack pesticidal effects of their own but enhance the pesticidal effects of other chemicals. Benton County Mosquito Control uses Anvil 10+10 which has piperonyl butoxide as an active ingredient (synergist).

Deltamethrin

Deltamethrin is a pyrethroid but does not use any piperonyl butoxide in its formulation.  It is water-based and is commonly diluted with water at varying ratios (we use a 2 parts water to 1 part DeltaGard ratio for our applications). Benton County Mosquito Control uses DeltaGard.

Truck Application Example

The current application rate of Anvil 10+10 is 0.62 fluid ounces per acre.  The name Anvil 10+10 tells us that 10% of the product is sumithrin (a pyrethroid) and 10% is piperonyl butoxide (a synergist); these are the active ingredients. The remaining 80% of the product (i.e. "Other Ingredients") are not insecticides are primarily work as a carrier (oil) for the active ingredients.

If our application rate is 0.62 fluid ounces per acre, then only 20% of this amount is actual pesticide.  So, only 0.124 fluid ounces of active ingredient are applied per acre, which works out to 1 fluid ounce for every 8 acres.  This incredibly small amount can be used because (1) mosquitoes have a low body mass and don’t require much insecticide to kill them and (2) we use ultra-low volume (ULV) technology in our truck foggers, which allows very small droplets to be formed.

The current application rate for DeltaGard is 2.01 fluid ounces per acre.  But, DeltaGard is only 2% active ingredient (no PBO is used) and we dilute it at a 2:1 ratio.  So, out of the 2.01 fluid ounces per acre of final product, only 0.013 fluid ounces per acre is active ingredient being applied.  Which would mean that 1 fluid ounce of active ingredient would cover 77 acres.  This incredibly small amount can be used because (1) mosquitoes have a low body mass and don’t require much insecticide to kill them and (2) we use ultra-low volume (ULV) technology in our truck foggers, which allows very small droplets to be formed.

Adulticides We Use in Planes:

Naled

We use a different chemical, naled, by air because it is dense(15 lbs/gal), therefore it can penetrate thick vegetation to come in contact with flying mosquitoes.  It is approved for use over residential areas, marshes, wetlands, crops, and pastures – all things we have within the Benton County metro area.  It also breaks down within hours of application reducing any long-term effects on the environment.  

Naled will cause eye irritation if you are directly in contact with the spray cloud.  It takes about 20 minutes for the product to drop from the release height of the plane, so if you see it fly over you have time to get inside.  Please click the link regarding Naled use for mosquito control from the EPA:  Naled

Does Naled Pose Risks to Human Health?
Naled can be used for public health mosquito control programs without posing unreasonable risks to the general population when applied according to the label. We have estimated the exposure and risks to both adults and children posed by ULV aerial and ground applications of naled. Because of the very small amount of active ingredient released per acre of ground, the estimates found that for all scenarios considered, exposures were hundreds or even thousands of times below an amount that might pose a health concern. These estimates assumed several spraying events over a period of weeks, and also assumed that a toddler would ingest some soil and grass in addition to skin and inhalation exposure. However, at high doses, well above those for normal labeled uses, naled like other organophosphates, can overstimulate the nervous system causing nausea, dizziness, or confusion. Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis and death.

Adulticiding occurs near or after sunset and often after temperatures have dropped below 80 degrees Fahrenheit. This greatly reduces the potential contact that bees could have with adult mosquito sprays and vice versa.  But the District takes additional steps to try and reduce potential risk.

If you are registered commercial or backyard beekeeper with Washington State Department of Agriculture (WSDA), please contact us so we can be aware of where your beehive(s) are located.

If you are NOT a registered beekeeper, Revised Code of Washington (RCW 15.60.021) requires that "(1) Each person owning one or more hives with bees, brokers renting hives, and apiarists resident in other states who operate hives in Washington shall register with the director by April 1st each year."

The registration is one method we use to try and open up lines of communication with local beekeepers.  Please use this link to learn more about the registration process; WSDA Apiary and then give us a call.