Cache Mosquito Abatement District (CMAD)
Field workers use a white cup on the end of a pole to dip water to check for the presence of mosquito larvae.
Education
Our goal is not to eliminate each and every mosquito; CMAD instead seeks to control them to reduce the likelihood of disease and as nuisance abatement. Rather than blanketing the District with pesticide all the time, we use an Integrated Pest Management (IPM) program consisting of surveillance, larvacide, and adulticide.
Surveillance
CMAD uses a variety of surveillance methods. At the start of each mosquito season, generally sometime in May, our field workers start dipping. They visit standing bodies of water and use a white cup on the end of a pole to dip out some water. Mosquito larva, although very tiny, will show up as dark specks or rods against the white cup. If larva are found, then the larvacide is dispensed.
Also in May we decide where to place our mosquito traps. Using a CO2 tank to attract the female mosquitoes, we trap them overnight once a week. The traps are collected the following morning and taken back to the lab where the mosquitoes are counted and then, by using a dissecting microscope, they are also divided into species. In our District, the Culex species of mosquito typically carries West Nile Virus and Western Equine Encephalitis.
Larvacide
We use different types of larvacide depending on what else is present in the water and on the size or surface area of the water. If the body of water is small enough and if fish or other aquatic residents are present, we use a product made from bacteria that targets only mosquito larva. In other cases, such as a large body of still water, we'll use a pesticide mixed with a small amount of oil. This forms a very thin film on the surface of water that prevents the larva from getting oxygen to breathe, thus suffocating them.
Adulticide
Currently, CMAD uses a truck-mounted fogger to treat adult mosquitoes. The pesticide used is malathion. It has been approved for use since 1956 and recently (2006) underwent a detailed study on its safety to non-target organisms (people, particularly children; animals; birds). Many toxicity studies have been done with malathion; at the level/concentration we use, it is well under the approved limit from EPA.
Our field workers receive training on the application of pesticides and are certified by the Utah Department of Agriculture and Food as applicators. The fogging machines are tested and calibrated each year to ensure they are delivering the target amount of pesticide at a specific vehicle speed (anywhere from 12 mph up to 23 mph). Please note that some of our fogging machines are designed to turn off the flow of pesticide solution yet still allow the motor on the fogging pump to continue running. This feature allows for better control of the application (avoiding bee hives, organic farms, etc.).
Our goal is not eradication of mosquitoes but to control them to reduce the spread of disease and their nuisance factor. Generally, fogging is done in the evening between dusk and 1:00 a.m. This is when mosqitoes such as the Culex species is most active and therefore most likely to be killed by the pesticide. Bees return to their hives at dusk and so are not likely to be exposed to the pesticide. Malathion breaks down relatively quickly in our environment (less than a day).
