A community
can best handle mosquito problems when an organized abatement district
(tax-supported) is established. Qualified personnel with adequate
funds can then be hired to conduct an effective mosquito-control
program. Under Illinois law, the Mosquito Abatement Districts Act
(70 ICCS 1005/et. seq.) enables voters, by referendum, to organize
tax-supported mosquito abatement districts.
In
an area without a mosquito abatement district, local community leaders
must direct and implement the program themselves; successful programs
must have persons who are qualified to direct effective mosquito-control
operations. This fact sheet is intended to assist communities that
are not part of an established abatement district. Professional
advice can be obtained by contacting:
Illinois
Department of Public Health
Division of Environmental Health
525 West Jefferson Street
Springfield, IL 62761
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or
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University
of Illinois
Extension Entomology Office
172 Natural Resources Building
Champaign, IL 61820
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or
your unit office of the University of Illinois Cooperative Extension
Service. In addition, the following facts about mosquitoes and suggestions
for their control should be helpful.
Mosquito
Facts
Mosquitoes are among the most common pests of people. Their biting
is an annoyance and an irritation. They can carry numerous diseases
that affect humans and their pets or livestock. In Illinois, although
disease transmission is extremely rare, there are 3 kinds of encephalitis
(St Louis Encephalitis, La Crosse Encephalitis and Western Equine
Encephalitis) which mosquitoes can transmit to humans, as well as
a nematode affecting dogs (dog heartworm).
Although,
disease transmission is the most commonly cited reason for considering
mosquitoes to be a public health problem, the presence of large
numbers of biting pests will influence the physical and mental well
being of most people. Mosquitoes also cause economic loss to livestock
as a result of blood loss and irritation. In addition, mosquitoes
can reduce recreation activities which will result in a loss of
tourist income, and they can depress property values on land adjacent
to areas where they are produced.
Immature
mosquitoes are worm-like creatures called larvae that need to live
in water while they feed on the microbes or decaying organic matter.
Depending on the species, the adult female lays her eggs on standing
water or in places that later become flooded. Larvae are rarely
found in lakes and ponds with deep water and clean margins (without
excessive vegetation and stagnant pools) or in flowing water such
as streams and rivers. Mosquitoes can be classified by where the
larvae are found:
- floodwater
or temporary pool
- treeholes
and artificial containers
- standing water
Knowing which type of habitat a mosquito species prefers will help
in providing effective control.
Generally,
the peak biting periods of mosquitoes occur just before and after
dark, and again just before dawn. However, each species has its
own peak period of biting activity. Male mosquitoes do not bite,
but feed on the nectar of flowers and plant juices. At other times,
outside the biting periods, adult mosquitoes can be found resting
in grass, shrubbery, or other foliage.
A Synopsis
of the Mosquitoes of Illinois by H.R. Ross and W. R. Horsfall published
in 1965 as "Illinois Natural History Survey Biological Notes
No. 52" is still used by many mosquito control districts as
an aid to developing their own key. No keys are perfect. In general,
it is best to acquire some training in mosquito identification from
someone trained in Medical or Veterinary Entomology before attempting
to identify mosquitoes. Most trained entomologists develop their
own keys and rely on mosquito taxonomists for further help.
Floodwater
and temporary pool mosquitoes common to Illinois include the
inland floodwater mosquito (Aedes vexans), the saltmarsh
mosquito (Aedes sollicitans), and the dark rice-field mosquito
(Psorophora columbiae). The eggs of these mosquitoes, which
are laid singly on damp soil, require a drying period and may remain
dormant for months, hatching within minutes after being covered
by shallow water. The inland floodwater mosquito breeds in areas
subject to flooding, such as marshy areas, low wetlands, or poorly
drained areas, and is the most important pest mosquito in the state.
The saltmarsh mosquito is found chiefly in southern Illinois in
association with improper handling of sulfuretted wastes from strip
mines and salt water from oil-field operations. The dark rice-field
mosquito and other closely related species will develop in temporary
pools, roadside ditches, shallow depressions, and even wheel and
animal tracks that fill up during rains.
Floodwater
and temporary-pool mosquitoes will complete their development from
egg to adult in 8 to 14 days. There can be several generations a
season if there is adequate rainfall to flood or inundate their
egg-laying sites. Heavy populations occur in 10 days to two weeks
after the egg-laying sites are flooded. The adults are persistent
biters and will bite throughout the day if disturbed. Most floodwater
mosquito species are strong flyers. Over a period of days, they
may migrate several miles from their breeding sites. These factors
make the floodwater mosquitoes very serious pests in Illinois.
The
tree-hole mosquito, Aedes triseriatus, can be a serious
pest near wooded areas, as the females are easily disturbed and
will bite throughout the day. Eggs are laid singly just above the
water line in tree holes and hollow stumps or artificial containers
like old tires. As rainfall fills these cavities and covers the
eggs, the larvae hatch and develop. The tree-hole mosquito is a
carrier (vector) of LaCrosse Encephalitis.
The
Asian tiger mosquito (Aedes albopictus) is another species
which can be found associated with artificial containers, especially
old tires. In Asian countries this recent immigrant carries encephalitis
or other viruses to humans. It is an aggressive species which feeds
throughout the day.
Standing-water
mosquitoes, such as the northern house mosquito (Culex pipiens)
and related species, develop in overgrown ponds, stagnant and shaded
pools, poorly managed waste-effluent lagoons, catch basins, puddles
in drainage ditches, as well as in artificial containers such as
old tires, tin cans, children's toys, bird baths, and roof gutters.
These mosquitoes lay their eggs on the surface of the water in groups
(rafts). The mosquito larvae become full grown in about 7 to 10
days and feed on bits of organic matter in the water. The pupae
transform into adults in 3 to 4 days. The adult female is ready
to bite in another day or two, remaining near the larval development
site in order to feed. The northern house mosquito is an important
vector of St. Louis encephalitis.
The
larvae of Anopheles quadrimaculatus, which was the primary
vector of malaria in the eastern United States, are primarily found
in permanent fresh water pools, ponds, and swamps that contain aquatic
vegetation or floating debris. The females lay their eggs singly
on the surface of the water. Although malaria no longer is a threat
in Illinois, the malaria mosquito can be a serious pest near wetlands.
Suggestions
for Controlling Mosquitoes in a Community
- Determine the Species Present. Monitor mosquito populations during
the summer with light traps, biting counts, and other methods.
(See "Mosquitoes in Illinois: Recommendations for Prevention
and Control" by the Illinois Department of Public Health)
- Locate Larval Development Sites. Locate and map "mosquito
breeding sites" both within and for at least 5 miles (preferably
15 miles) outside the city. Outlying flooded areas must be managed
for successful suppression of floodwater (Aedes) mosquitoes.
Continue to watch for new sites or sites overlooked in the initial
survey.
- Eliminate Larval Development Sites. Make short-term and
long-term plans to eliminate as many of the mapped sites as possible
by leveling, filling, and draining. Pay particular attention to
drainage ditches, catch basins, grassy depressions and lowland
areas. Consideration must be given to the legal aspects of mosquito
control in wetlands or wildlife habitats.
- Clean Water Margins. Remove vegetation and debris along
the margins of ponds, lakes, and streams and fill or drain backwater
pockets. Do not allow vegetation to overhang the water. Mow the
grasses and weeds along the margin frequently. Stock the water
with top-feeding minnows. Contact your local State Department
of Natural Resources Office (usually located in the county seat)
to determine which species of minnows can be released for control
of mosquito larvae.
- Use Insecticides as a Supplement to Cultural Practices.
Anyone who conducts mosquito control on property other than their
own must have a General Standards (Operators) Exam license and
be supervised by a Licensed (Category 8) Applicator. The Illinois
Department of Public Health supplies study materials for this
test which is administered by the Illinois Department of Agriculture.
Training sessions are conducted in the winter by the University
of Illinois Cooperative Extension Service. The study text used
for the Category 8 examination, "Mosquitoes in Illinois:
Recommendations for Prevention and Control", is an excellent
source for general insecticide information. It can be obtained
from the Illinois Department of Public Health and the University
of Illinois Cooperative Extension Service.
In Illinois there are no legislated regulations governing decisions
on when to apply insecticides for mosquito control, as long as pesticide
label instructions are followed. Some communities have developed
thresholds for various species beyond which action is taken. With
the appropriate experience, larval population numbers can be used
to predict when resulting adult populations will rise beyond the
level tolerated in a community. Although this sort of data may take
some time to develop, it may be both a time and money saving technique
in the long run. Some communities practice tighter larval control
inside community environs than in the surrounding regions.
To
control mosquito larvae or wigglers. Check for the presence
of mosquito larvae with a white dipper. Apply an insecticide treatment
according to label directions to stagnant water areas when the determined
number of larvae are found. Repeated treatments will be needed during
periods of mosquito abundance. A single treatment should stop the
emergence of new mosquitoes for 10 to 14 days. Treehole mosquito
populations are more difficult to sample, but the best treatment
remains the removal or drainage of artificial containers.
To
control mosquito adults (for emergency relief when adult mosquitoes
are numerous). Apply a fog to grass, weeds, and shrubs; along wooded
areas, ditches, roadsides, and parking lots; and in parks and around
the perimeter of playgrounds. Fogs kill only those mosquitoes hit
by the chemical. Their effect is of short duration, usually a matter
of a few hours to a few days. Fogging is best done in the evening
just before or just after dark when mosquitoes are most active and
when atmospheric conditions are such that the fog will remain near
the ground. Do not apply the treatment if the air temperature is
below 60° F or as stated on the insecticide label. Fogging at
other times of the day has an arguable psychological benefit but
does not eliminate as many adult mosquitoes. Repeated treatments
will be needed, and their frequency will depend on the effectiveness
of the larval-control program and frequency of rainfall. A control
program aimed at only the adult mosquitoes is rarely satisfactory
because not all the adults are killed and additional ones are produced
or rapidly move into the treated areas.
Type
of application equipment to use. Thermal fog generators are
available for applying fogs. Ultra-low volume (ULV) applicators
are available, or existing equipment can sometimes be adapted to
apply the undiluted concentrate as a fine aerosol or cold fog. Power
sprayers or small hand-operated tank sprayers can be used to apply
larvicides, spray catch basins, or apply a residual "barrier
treatment" along the margins of a woods. Granular and briquet
formulations of mosquito larvicides are also available for treating
small larval sites such as ditches or catch basins. All mosquito
control personnel must be licensed by the Illinois Department of
Agriculture.
Precautions.
KEEP THE PUBLIC INFORMED about mosquito control operations. Before
any applications of fogs are made, notify the public of the date
and time of applications whenever possible. Individuals with severe
allergy conditions and persons with asthmatic problems may wish
to stay indoors or plan to be away from the community during the
treatment hours. Car finishes may be spotted with certain insecticide
sprays and owners may wish to house them in the garage during the
treatment hours. The understanding and cooperation of the general
public are necessary if the program is to be a success.
For
individual homeowners. A fact sheet on mosquitoes and their
control in and around the home is available as NHE-94 from the your
unit office of the University of Illinois Cooperative Extension
Service. The efforts of individual homeowners to control mosquitoes
on their properties can greatly enhance the success of a community
in solving mosquito problems.
For
more information on managing mosquitoes and chemical recommendations,
see the University of Illinois Urban Pest Management Handbook or
contact your unit office of the University of Illinois Cooperative
Extension Service.
Prepared
by Entomologists at the University of Illinois, Illinois Natural
History Survey, and Illinois Department of Public Health. For additional
copies, contact your unit office of the University of Illinois Cooperative
Extension Service.
Urbana,
Illinois 1995. Issued in furtherance of the Cooperative Extension
Work Acts of May 8 and June 30, 1914, in cooperation with the U.S.
Department of Agriculture. Dennis R. Campion, Interim Director,
Cooperative Extension Service, University of Illinois at Urbana-Champaign.
Entomology
Fact Sheet, NHE-132, Revised 4/96
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