It is a very common misconception among the public that streams, ponds and lakes and are mosquito breeding habitats. Mosquitoes cannot breed successfully in flowing water, and streams can only produce mosquitoes when they dry up and leave shallow, stagnant puddles in the stream bed. Although it is true that your average farm pond can produce a few mosquitoes (e.g., 1-2 mosquitoes per 50 ft of shoreline per week), these would all originate from narrow bands of emergent vegetation or stagnant inlets along the shoreline. A pond that has several hundred square feet of shallow marshy habitat on one end will be able to produce more mosquitoes. However, if a pond is deep, contains fish, or has been in existence for long enough to develop resident populations of predatory species (insects, frogs, spiders, etc.), it will not produce enough mosquitoes to be of any consequence. In contrast, a temporary body of water such as a 10 ft. long x 1 ft. wide x 6 in. deep section of flooded ditch or wheel rut can easily produce a thousand mosquitoes in a short period of time.
Mosquito larvae associated with permanent bodies of water generally live where the water is shallow (1 ft or less), and weeds, debris, emergent grasses or some sort of aquatic vegetation shelters the mosquito larvae from fish and other predators. Relatively few mosquito species actually breed in permanent bodies of water such as marshes or swamps. Most of the mosquito species associated with marshes or swamps actually breed in temporary pools along the margins of these habitats.
Any temporary body of water that is present for more than a week can be a mosquito breeding habitat. Flooded cattle hoof prints in a muddy field have been known to produce dozens of mosquitoes each. The limiting factors are the longevity of the aquatic habitat, and the duration of the mosquito species' life cycle (life cycle = time from egg hatch to emergence of adult mosquitoes from the water). The shortest life cycle on record for a mosquito is about 4.5 days, and this particular species breeds in mid-summer in the sun-warmed puddles of flooded fields, or areas of forest clear-cut (e.g., wheel ruts).It can only develop this quickly when the water conditions (i.e., temperature and food supply) are ideal. Other mosquito species typically have life cycles that take at least one or two weeks. Thus, most mosquito species can complete their life cycle in a flood pool or puddle that is present for more than 2 weeks, but will not be able to survive in a puddle that dries up after only one week.
Citizens who complain about mosquitoes in their neighborhood often focus on a nearby pond or stream as the source of their problem. Knowledge that ponds or flowing streams are generally not the source of a mosquito problem, and that temporary bodies of water are very often the source, will save personnel much time and effort when they go to investigate a mosquito complaint.
Dr. David N. Gaines
Public Health Entomologist
VDH-Office of Epidemiology
(804) 786-6261
