The Southern Nevada Health District conducted its first mosquito fogging operation in the area bordered by the cross streets of Alexander Road and Decatur Blvd. and Valley Drive and Gowan Road, on Friday, June 9 between the hours of 1 a.m. and 5 a.m. Trucks applied Duet, a product registered for mosquito control by the U.S. Environmental Protection Agency comprised of active ingredients for mosquito control recommended by the Centers for Disease Control and Prevention. Working with local jurisdictional partners, additional mosquito fogging will be scheduled as needed to control the adult mosquito population in Southern Nevada.

Spraying activity is conducted overnight to avoid harming beneficial insects that are active during the daytime hours.

Duet is the name of a public health mosquito control product. It has two active ingredients: Sumithrin and Prallethrin. They are formulated to mimic the insect-killing (insecticidal) properties of natural substances called “pyrethrins” in chrysanthemum flowers. Duet was registered by the U.S. EPA in 1995 to help control adult mosquito populations that may transmit disease.

When applied as indicated on the label for adult mosquito control, Duet does not endanger human health. Prior to registering a product, the EPA evaluates products thoroughly to be sure there is a “reasonable certainty of no harm” to humans, animals and the environment from their use. Duet and its ingredients have passed rigorous tests required by the EPA and have been approved for use in ground and aerial application in outdoor residential and recreational areas and other similar areas.

Duet is applied at extremely low dosage rates – less than an ounce per acre. An acre is equivalent to approximately a football field. Such low rates mean there is very low exposure even if present during or immediately after the application is made; this level of exposure is far less than the amount necessary to pose a health concern.

People and pets can be outdoors during the application; there are no re-entry restrictions or
limitations for Duet. If you choose to remain indoors, the spray (mist) will dissipate quickly through the treatment area (in 5-30 minutes, depending on weather conditions). The low application rate and wide area dispersal of the spray ensure that exposures are minimal.

No. The ingredients of Duet are not corrosive or staining and therefore should cause no chemical harm to the finish of a car or house.

No. It is not necessary to close doors or windows. The spray will dissipate from the treated area quickly (within 5-30 minutes).

No. There is no need to take any precautions with air conditioning systems.

No special precautions or waiting periods are recommended for outdoor swimming pools. However, if a pool is not being used during the summer months (e.g., if it not being chlorinated or filtered), it should be covered or drained. Any standing body of water is a potential breeding ground for mosquitoes.

No. Duet will not deposit in significant amount. Any residue will degrade quickly on exposure to sunlight. As good public health practice, the Health District recommends always rinsing fruits and vegetables with water as a precautionary measure.

No. The spraying should not pose a risk for a healthy pond.

No. Horses and livestock should not be adversely affected by applications of Duet. Its ingredients are commonly used in livestock pest management products.

Because of the way in which Duet is applied and the time of day it is applied, it should not impact beneficial insects, like bees and butterflies. Duet is applied in small droplets, which break down quickly in the environment. Since the product must hit a mosquito while it is in flight to have an effect, it is sprayed at night when mosquitoes are actively flying and when other insects, such as bees and butterflies, are not active.

However, Duet is an insecticide and may be toxic upon direct exposure to bees active outside the hive. Beekeepers can protect their bees by sheltering the hives during the spraying operations.

The U.S. EPA has determined that Duet can be applied by truck or aircraft in residential and recreational areas, including vegetation surrounding parks, overgrown areas, and golf courses without undue risk to the environment.

Generally, Duet is applied at an ultra-low volume in an extremely fine mist of tiny drops, where the average droplet size is 17 microns – smaller than the size of a pinpoint. It can be applied via ground (truck or backpack) or from the air.

Duet is applied in very low dosages, from less than half an ounce to a little more than one ounce of formulated product per acre (.43 to 1.28 fl oz/ac). This is approximately a tablespoon of formulated product to treat an area the size of a football field.

This will not completely eliminate all mosquitoes. Killing adult mosquitoes (adulticiding) – or spraying – helps to control the size of mosquito populations and prevent the spread of disease. Mosquito populations are constantly dying off and regenerating, and adulticiding will not eliminate all of the adult mosquitoes in the community. Adulticiding is needed because source reduction (reducing unnecessary standing water), surveillance and larviciding (killing the mosquito population at the larval stage) alone are not enough to control mosquito populations.

Duet is effective in controlling disease-spreading mosquitoes. A specific area is identified and treated, but the spraying in this targeted area is not reaching an entire habitat of mosquitoes. Sometimes mosquitoes move into the spray zone from outside of it after it is treated, which is called “reinfestation” (i.e., they drift in on wind currents from areas that have not been treated). When mosquito reinfestation occurs, additional sprayings may need to be considered to control the spread of mosquitoes that transmit disease. Effectively controlling an adult mosquito population through spraying also depends on a number of external factors, including timing, the level of reinfestation, methodology used during the application and weather conditions.