Mosquitoes

This spring's abundant rain has created the potential for an upsurge in mosquito activity that may be "felt" by many people over the next few weeks. The only reason we have not felt the problem before now is that our unseasonal cool temperatures have slowed the mosquito developmental rate and delayed adult emergence in many areas of the state. Regardless of whether record numbers of mosquitoes are produced this year, many people are now asking how to control these pests in and around their homes. The first and most important thing to remember is that while there are several options available to reduce the number of mosquitoes breeding on your premises, this may not result in a reduction in mosquito numbers or biting activity. To put it very simply, our most common species of mosquito can migrate several miles from where it developed. Therefore, you could eliminate all mosquito breeding on your property and still be bothered by mosquitoes migrating into your backyard from adjacent areas.

Adulticiding is one option available for mosquito control. However, it does have its limitations. Coarse sprays of products such as Sevin, Dursban, malathion, or resmethrin applied to shrubbery and other dense, low-growing vegetation can reduce adult mosquitoes for a few days. This is fine if the application is made the day before a backyard picnic or family gathering but has little benefit in reducing adult mosquitoes for an extended period of time. Hand held foggers or foggers that adapt to lawn mowers can also provide temporary relief from adult mosquitoes but will also have no lasting effect. The best option for mosquito control is to target your control efforts at the larval stage. Any area or object that can hold water for a period of one week should be filled, drained, or discarded. This includes areas such as stagnant puddles, pools or ditches, and objects such as cans, buckets, old tires, clogged rain gutters, bird baths and child wading pools. A number of insecticides are also available for application to a body of water to control mosquito larvae. However, before applying any insecticide to a body of water you need to ask the following questions. First, can the body of water be effectively drained or filled so that no application is needed. Second, are there enough mosquito larvae present in the water to warrant an application. And third, are there fish or other aquatic wildlife present in the body of water that might be damaged or killed if an application is made. These are critical questions that need to be answered. Contrary to popular opinion, not all bodies of water serve as abundant mosquito breeding areas. For example, ponds that have steep banks, are relatively free of organic matter, and have little or no vegetation extending into the edge of the pond will typically produce very few mosquitoes. In contrast, shallow marshy areas can serve as a breeding area for tremendous numbers of mosquitoes. For bodies of water that hold fish or other beneficial aquatic wildlife, products such as Altosid, Bactimos, Teknar, and Vectobac can be safely used.

Whether mosquitoes are developing on your property or in adjacent areas, the use of mosquito repellents can provide protection against biting activity. Products that contain the active ingredient N,N-diethyl-metatoluamide (DEET) are the products of choice and should provide protection for several hours.

This article originally appeared in the May 26, 1993 issue, p. 81.