Mosquito Breeding Habitats
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
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