Mosquito populations in Iowa are determined primarily by the frequency and amount of rain that falls during the course of the spring, summer, and early fall. Mosquitoes have a complete life cycle of four stages: Egg > Larva > Pupa > Adult. The first three stages occur in standing water. The eggs hatch when exposed to water; the larvae ("wrigglers") feed and grow in water; pupae ("tumblers") remain in the water while they transform to the flying adult. The life cycle typically takes up two weeks, but may take as little as a week or as long as a month. There can be several generations of mosquitoes each summer. “Mosquito season” generally lasts from May through September in Iowa.
Only female mosquitoes bite and feed on the blood of humans or other animals. Blood provides the nutrition the female needs to produce eggs to produce offspring of the next generation.
Mosquito Management in the Home Landscape
Individual efforts to reduce the number of mosquitoes on your property may provide limited, short-term benefit. Even if you eliminate all mosquito breeding on your premises you may not see a reduction in mosquito numbers or biting activity. Mosquitoes have no respect for property lines and can fly several miles from where they developed and migrate into your backyard from adjacent areas.
To reduce mosquitoes developing on your property eliminate all possible standing water sources in which mosquitoes could breed. Eliminate and dispose of cans, tires, and other objects that could hold water. Repair clogged rain gutters, and turn over toys, buckets, bins and other items that catch water. Drain, fill or ditch low-lying areas that hold water for several days following a rain.
Temporary or permanent water impoundments that can't be eliminated should be inspected weekly for the presence of developing mosquito larvae. If mosquito larvae are found and cannot be physically removed, consider treating the standing water with a mosquito larvicide. Before applying any insecticide to a body of water determine there are enough mosquito larvae present to warrant an application. Ponds that have steep banks, are relatively free of organic matter, and have little or no vegetation extending into the edge of the pond produce very few mosquitoes compared to shallow marshy areas can serve as a breeding area for tremendous numbers of mosquitoes.
Products suggested for homeowners will contain the insect growth regulator methoprene or the bacterium specific to mosquito larvae, Bacillus thuringiensis israelensis (Bti). When used according to label directions, these products will effectively control mosquitoes and are harmless to humans, pets, fish, and other types of wildlife. Some insecticide cannot be applied to water containing fish or other aquatic wildlife. Read and follow label directions.
Sprays and fogs applied to control mosquito adults (adulticides) are best suited for communities or large areas. Homeowner sprays and fogs are generally short-term in their effectiveness and have little benefit in reducing adult mosquitoes for an extended period of time. Homeowner options for treatment include ready-to-use aerosol, fogger, garden sprayer, or hose-end applicator. Insecticide sprays for mosquitoes should be directed to tall grass, flower beds and shrubs, underside of the deck and other areas where mosquitoes rest. Treatment may reduce adult mosquitoes for a day or two (such as the day before a backyard picnic or family gathering).
With all lawn and garden insecticides, the minimum re-entry interval is “after the spray has dried.” Time required to dry depends on humidity and moisture at the time of application and may vary from minutes to hours to overnight, depending on conditions. Check for reentry statements and other restrictions on the pesticide label and remember to read and follow label directions.
The practical alternative for dealing with mosquitoes is to avoid outdoor activity during peak mosquito activity times (one hour before until one hour after sundown), wear light color and loose-fitting clothing, and use personal repellents for short-term protection against mosquito biting.
Pick the repellent ingredient with a low to moderate concentration of active ingredient that best meets your needs. Use repellent sparingly to reduce unnecessary or excessive exposure and don’t apply repellent near eyes, on lips, or on broken skin. Apply to your face by spraying your palm and then spreading the repellent carefully. Don’t use near food. Wash repellent off with soap and water when it’s no longer needed. See the CDC website for more information on repellents.