Every year we deal with mosquitoes in Minnesota. There has been concern that mosquito numbers could be substantially higher this season because of river flooding in many areas of the state. The good news is that these flooded areas should not increase mosquito numbers much.
Spring mosquito species, such as Aedes stimulans, are usually not numerous enough to cause much problems. Also their breeding sites are not typically found in areas that have been flooded. The primary summer species, Aedes vexans, requires warmer water temperatures and does not emerge until late May or early June. By then, most of the flooded areas should have receded, reducing potential larval habitat. While flooding will have little impact on mosquito numbers, rainfall is much more important influence on their relative populations. The more rain we receive, the more mosquitoes will be produced. If we experience a dry year (2012, 1988), we will see fewer mosquitoes.
Regardless of how abundant mosquitoes are, their control is very challenging. To have any chance at being successful, a control program is best done on a large scale (e.g. the Metropolitan Mosquito Control District treats mosquitoes in the seven county area around Minneapolis and St. Paul). The best method to control mosquitoes is to treat the larvae. They breed in standing, shallow pools of water (of which there is great abundance of in Minnesota). Larvae are treated with Bacillus thuringiensis var. israliensis (B.t.i.) or methoprene. Homeowners can buy B.t.i., but because they are treating just small areas, they are very unlikely to get good results. Spraying adult mosquitoes is not very effective or practical. At best, it should be only considered for special events or emergency spray programs of disease-infected mosquitoes.
So what can a person do? There is no guaranteed method to completely avoid mosquitoes. You can try the following these guidelines. Keep in mind that you can follow these suggestions and still have a problem with mosquitoes.
Cut weeds and tall grassy areas near your home to help reduce mosquitoes harborage areas. Leave yard lights off when possible to avoid attracting them unnecessarily. You can also try less attractive lights like sodium lights as fluorescent or incandescent lights are more attractive to mosquitoes. Make sure that window and door screens fit properly. Repair or replace any screens with holes or tears. Remove any containers that may hold water (e.g. old tires). If they can not be removed, then drain them. If this is not possible, then apply a small amount of vegetable oil on the water's surface (this will suffocate any larvae in the water). Keep gutters cleaned so water doesn't accumulate.
Mosquitoes are most active early in the morning and at dusk. Try to avoid those times when possible. If you find yourself out when mosquitoes will be a problem, protect yourself by wearing long-sleeved shirts and long pants. Use a repellent. DEET (N,N-diethyl-meta-toluamide) is the most effective. Apply DEET to clothes or skin but only enough to lightly cover the desired areas. Do not over apply repellents! Do not treat children with a product containing more than 15% DEET. Always read product information thoroughly before using.
Published in Yard & Garden Line News, May 15, 2001