Mosquito Management Can Help Reduce Chances of Breeding, West Nile Virus

Despite a long dry-spell in Colorado during late spring and early summer, there is still plenty of time for mosquito populations to swell, thanks to recent wet weather much of the state has experienced over the past few weeks.

     "It may be later in the season, but there is still enough time for the life-cycle of the mosquito population to get going," said Chester Moore, a professor in Colorado State University’s College of Veterinary Medicine and Biomedical Sciences and College of Agricultural Sciences. Mosquitoes can carry on with their breeding cycles into September, he said.

     Moore doubts the recent rainfall would increase the chances of the West Nile Virus afflicting large numbers of people as it did in 2003.

Proper mosquito management can help reduce the chances of people and animals being bitten by mosquitoes, and contracting West Nile virus and other diseases. Colorado State University Cooperative Extension has several information resources available to the public about mosquito management.

Steps can be taken around the home to prevent biting-mosquito populations.

– Eliminate standing water, which is mosquitoes’ habitat, by draining low spots and ditches.

– Empty rainwater receptacles, such as bird baths, old tires, etc., at least once a week or cover or remove them.

– Place mosquito netting and tight screens around patios to create mosquito-free areas.

– Reduce unnecessary lighting around a home – mosquitoes are attracted to lights. Bug zappers are not effective at reducing mosquito populations and may kill beneficial insects that prey upon mosquitoes. Ultrasonic devices, such as those that claim to mimic dragonflies, do not affect mosquito activity.

– Adult mosquitoes rest in shrubbery and other shaded areas during the day. These areas can be treated with approved insecticides. Foggers for flying insects can also be used but will provide only short-term relief. Various aerosol insecticides are available for controlling mosquitoes indoors.

– Mosquito-eating fish, fathead minnows and a fish called Gambusia, can be released in bodies of water with mosquito habitat.

– Chemicals, referred to as larvicides, can be used in some habitats to kill mosquito larvae. This is generally the most economical and effective method of chemical control because the larvae are contained in water-filled habitats.

The best mosquito management is preventative and occurs before biting adults appear, but some measures can be taken later in the season to control their populations. The most typical form of controlling adult mosquitoes is applying insecticide, often called adulticiding or fogging. These insecticides are applied over a large area or on a community basis because mosquitoes are strong flyers.

Personal protections, including recommendations for using DEET:

-Light-colored clothing is less attractive to adult mosquitoes, and tightly woven fabrics give some protection against bites.

-DEET is considered the most effective mosquito repellent. However, there is concern about undesirable side effects on young children and others who might be unusually sensitive to this chemical.

– Apply DEET only to exposed skin and clothing, not to skin that will be covered with clothes.

– Avoid frequent reapplication or skin saturation.

– Do not apply DEET to cuts, wounds or irritated skin.

– Keep DEET away from eyes and mouth.

– Do not apply DEET to hands of young children.

– Use products with DEET concentrations of less than 20 percent on


– Do not spray DEET directly over the face.

– Avoid breathing DEET aerosol sprays.

– Wash treated skin and clothing after returning indoors.

Facts about mosquitoes:

– There are about 3,500 different kinds of mosquitoes. About 40 of these are found in Colorado. Not all types of mosquitoes feed on humans or transmit disease. Only a few of these kinds of mosquitoes are considered important transmitters of human disease.

– The lifecycle of a mosquito follows four distinct stages: egg, larva, pupa and adult. Eggs are laid in or near water and hatch into larvae. Larvae feed on organic material and small aquatic organisms. Pupae, which also are found in water, are the stage in which mosquitoes begin to transform into adults. Adults emerge from pupae to feed on blood from various hosts. Only the female mosquito can take a blood meal.

– During the summer, adult mosquitoes have a life span of a few weeks. However, some kinds of mosquitoes spend the winter as adults. Overwintering mosquitoes can live about six months, from late September to March.

– Adult mosquitoes can fly a mile or two to feed. Some mosquitoes have been observed to fly 10 miles or more.

– The buzzing sound of a mosquito is actually the unique wing beating frequency of females. This sound is attractive to male mosquitoes of the same species.

– Mosquitoes use a variety of cues to find their hosts, including chemicals such as carbon dioxide and lactic acid, as well as shape, color, heat and humidity. That’s why some people are bitten more often than others; individuals vary in the amount of these "cues" they produce.

For more information about mosquito management, visit or contact the local Colorado State University Cooperative Extension office, usually listed under the county government section of the local phone book.