Quick Access

Pest Management

Department Role in Mosquito Abatement


Mosquitoes are in the order Diptera ("two wings") one of the largest and most diverse insect groups. Their relatives range from predatory horse flies and robber flies to house flies, gnats, and fruit flies. A fair number of flies are even parasitic at some point in their life cycle. All flies go through complete metamorphosis (egg to larvae to pupae to adult) and have legless larvae.


Mosquitoes are very diverse, even by the standards of the Diptera. Their larvae are always aquatic, but are found in habitats from pools of glacial melt-water to hot springs, slow-moving rivers and lakes to small accumulations of water in containers and tires. Only the female mosquito bites (to obtain the blood meal she needs to make eggs), but most are very particular about what they bite. Some feed on mammals, some bite only birds, and some are specialized to feed on only amphibians or reptiles.


Mosquitoes lay their eggs in or near water. Some lay directly on the water, and the eggs hatch immediately. Some lay their eggs at some distance above the water line; these eggs hatch only when the area floods enough to cover them. This is why large numbers of mosquitoes seem to appear from nowhere after floods: the eggs are already there.


Mosquito-borne disease is fortunately not common in Montana. Several types of equine encephalitis, St. Louis encephalitis, and West Nile virus (another encephalitis) have been found here in the last few decades, but cases have been few and fatalities even fewer. The best protection against mosquito-borne disease is repellents such as DEET or picaridin, applied as directed on the product labels. Some "natural" or "soft" chemical repellents such as essential oils and plant extracts are effective, but do not last as long as DEET or picaridin. Electronic, magnetic, and ultrasonic devices have repeatedly and conclusively been shown to be utterly ineffective.


The aggravation caused by large numbers of mosquitoes is not insignificant, however. Landing rates of 3-5 mosquitoes a minutes are enough to interfere with normal outdoor activities, according to the Centers for Disease Control (CDC). At landing rates near 20 per minute livestock lose weight rapidly and human activity outdoors is difficult. After floods and hurricanes, CDC has recorded landing rates up to 200 mosquitoes per minute. This is more than enough to make repair and disaster-recovery efforts impossible.


Mosquito Abatement in Montana

There are a number of Mosquito Abatement Districts in Montana, and several towns have their own mosquito abatement equipment. In some areas private businesses are available to treat for mosquitoes. IPM mosquito-control methods do include conventional pesticide applications to knock down the nuisance populations of adults, but rely more heavily on population monitoring, treating or eliminating breeding sites (standing water, egg-laden vegetation in floodplains, old tires and other containers), and education of the public.


The Department of Agriculture is not directly involved in mosquito control activities. We do, however, regulate pesticide use, register mosquito-control pesticides and repellents, and license and recertify the pesticide applicators involved in mosquito control. We provide technical support and work closely with mosquito control districts to identify mosquitoes, train pesticide applicators, and ensure that the machines used for adulticide applications are properly calibrated.


Published: Wed Aug 10 16:54:00 MDT 2011.
Last Modified: Mon Aug 22 14:58:00 MDT 2016