High-moisture years often mean bumper years for mosquitoes. Although mosquitoes fly for long distances, some species can fly up to 40 miles in 24 hours, chances are good that many of the mosquitoes you find in your yard and home are being produced nearby. By eliminating the conditions they must have to survive, you can help reduce the numbers in your yard. And with a little cooperation from the neighbors, you may be able to minimize the mosquito problem even more.
Mosquitoes need areas that are periodically flooded or areas of standing or slow moving water to reproduce; eggs are deposited on the water, then hatch into small aquatic "wigglers". These wigglers then change to adults. So when control efforts are being made, it is important to consider any standing water in the area, whether it is from irrigation, flooding, runoff, or simply swampy edges around ponds or streams. Remember that extremely large numbers of mosquitoes can be produced in even a few cupsful of standing water.
Begin control efforts by looking around your yard and near your house and neighborhood, fields, or pastures, for standing water. Some of the more common sites include puddling from watering and irrigation, areas periodically inundated from stream runoff and snow melt, ponds, marshy areas, in hoof holes left by horses, elk, and other animals around watering areas, or rainwater accumulation that stands for 4 or 5 days. Later in the summer, standing water found in old tires, clogged roof gutters, boats or canoes that have not been drained, dripping outdoor faucets, and water leaks can support certain species of mosquito. However, humans are not the preferred hosts for these species so these sources of standing water are usually not main sources of the biting pests for humans, but can be sources for species that attack pets and livestock.
Periodically monitor standing water for larvae (“wigglers”), perhaps once a week, using a long-handled dipper. Mosquito-monitoring tools can be purchased through CENEX dealers. Be aware the larvae are quite sensitive to movement or vibration and quickly drop down from the surface of the water as you approach or try to scoop them into the dipper. A little practice will make it easier.
If you find mosquito larvae, drain or empty sources of standing water when possible. If it is not possible, or if the source of standing water is large, such as a pond, you might want to consider a biological control agent called BTI (Bacillus thuringiensis var. israelensis), which will kill immature mosquitoes (“wigglers”), black flies and fungus gnats, but is not harmful to humans, pets, or other organisms. Be sure you ask for BTI rather than just BT, which is effective for different insects. Slow-release BTI briquettes are available which require replacement only once every 30 or 90 days. If BTI sprays are used, they should be applied every 5 days during the breeding season. Aquatic surface films, also called mosquito larvicides, are specially formulated oils that suffocate mosquitoes. They can be quite effective and some are relatively safe for wildlife. Mosquito larvacides, which are primarily mineral oil with a small amount of spreading agent, are usually applied at rates of one quart/1,000 square feet of water (a strip 5 feet wide and 200 feet long, or an area approx. 31x31 sq. feet), or 2-4 tsp/100 square feet of water (a strip five feet wide and 20 feet long, or 10x10 sq. feet). The entire surface area of a lake or pond does not need to be treated, only a strip several feet wide next to the shoreline. BTI used in combination with aquatic surface films is more effective than either product used alone. Only the edges of ponds or lakes and adjacent marshy areas, where the mosquitoes are actually being produced, need to be treated.
Bonide also makes a granular product called Mosquito Beater which can be sprinkled in picnic or barbecue areas, or the backyard, and is said to offer protection for up to eight days by repelling mosquitoes. Two distributors for Bonide products in Montana are Garden City Seeds, in Hamilton, and some CENEX dealers.
Pyrethrin or malathion can be useful as a short-term control for adults mosquitoes when applied to picnic areas, yards, tall grass and shrubbery. However, these products can affect other animals and insects, including the beneficial organisms that help control a variety of pests. When using any insecticide, always read the entire label and follow directions carefully.
A wide variety of mosquito repellants are also available, including non-toxic citronella candles for porch and patio areas and non-toxic repellants for use on the body. However, the effectiveness of these biological materials has not been tested scientifically and mixed results are reported. You may want to try them and see for yourself. DEET, a readily available synthetic repellant, is very effective. Maintaining tight-fitting screens and weather stripping can help keep mosquitoes outside. Yellow light bulbs are non-attractive for many insect pests and can be used at building entrances.
References:
The IPM Practitioner. Bio-Integral Resource Center. Berkeley, CA 94707.
Mosquito Control Guide. 1996. Fifth Edition. VanDiest Supply Co. (Cornbelt Chemical Co.), McCook, NE 69001. 41 pp.
Olkowski, W., S. Daar, and H. Olkowski. 1991. Common-Sense Pest Control; Least-toxic Solutions for Your Home, Garden, Pets and Community. Taunton Press, Newtown, Connecticut. 715 pp.
Pacific Northwest Insect Control Handbooks. 1997. Extension Services of Oregon State University. Corvallis, OR 97331-0817.
Written by Sherry Lajeunesse, Extension Urban Pest Management Specialist. Sept., 1997
Categories: Mosquitoes, Insect
Date: 12/03/2001