Mosquito Management by Trained Personnel - Purdue Extension ...

Public Health
PURDUE EXTENSION
E-52-W
Department of Entomology
MOSQUITO MANAGEMENT BY TRAINED PERSONNEL
Ralph E. Williams, Extension Entomologist, Michael J. Sinsko, Public Health Entomologist,
Indiana State Department of Health, and Gary W. Bennett, Extension Entomologist
More than 50 species of mosquitoes are present in Indiana.
The biting of most species is simply annoying. However,
certain species (especially in the genera Culex and Aedes)
can threaten public health because of their ability to transmit
viruses that cause human encephalitis. Several such viruses
have caused disease outbreaks in various parts of the U.S.
over the last few years. In 1975, a strain of virus produced an
epidemic of St. Louis Encephalitis in Indiana causing illness
and death in several counties. This virus is transmitted from
birds to humans by mosquitoes. A limited number of mosquitoes
can transmit the virus, and prime concern is centered
on species of Culex mosquitoes.
Other mosquito-borne viruses that have been of concern
in Indiana include those that are responsible for causing such
diseases as La Crosse fever, Eastern equine encephalitis, and
Western equine encephalitis. Recent concern has focused
on the spread of West Nile virus. With this virus, like many
of the other mosquito-borne encephalitis viruses, wild birds
serve as the reservoir. Mosquitoes feed on infected birds and
transmit the virus to other birds. Infected birds may become
ill and recover or may exhibit no noticeable symptoms. Wild
birds may also die of the infection, however. Crow mortality
has been high.
The virus becomes widespread in the wild bird population
by midsummer, when mosquitoes are abundant. The likelihood
that mosquitoes will become infected and transmit the
virus to dead-end hosts such as people and horses is highest
between July and late October. A few Culex species are the
probable vectors of West Nile virus. Aedes albopictus (Asian
tiger mosquito) is also of concern.
Steps that can be taken to protect individuals and their
homes are described in the Purdue Extension publication
E-26, “Mosquito Control in and Around the Home” . But steps
taken by individual homeowners will not completely eradicate
the problem. To reduce annoyance and public health concerns,
mosquito management should be undertaken on an area-wide
basis by trained personnel.
Mosquito feeding on an arm.
(Photo credit: John Obermeyer)
MOSQUITO BREEDING AND DEVELOPMENT
Mosquitoes always develop in water, but the type of breeding
place varies with the species. Common breeding places
are flood waters, woodland pools, and slowly moving streams
and ditches, particularly if these moving waters are polluted
with organic waste. They also develop in any container that
holds water, such as tree cavities, rain barrels, fish ponds,
house gutters, down-spouts, bird baths, old tires, tin cans,
and catch basins.
Mosquitoes lay eggs on the surface of water or in low
places where water is likely to accumulate. The eggs may
hatch in fewer than three days or when flooding occurs. The
larvae, commonly called “wiggle-tails,” mature in 7 to 10 days
and change into a pupa or “tumbler” stage. Two or three days
later, adult mosquitoes emerge. After taking a blood meal,
each female lays 100 to 200 or more eggs. The entire life
cycle, depending upon temperature, may be completed in as
few as 7 to 10 days.

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Larva
Pupa
Adult
Mosquito adult, larva and pupa
AREA-WIDE MANAGEMENT
Mosquito management on an area-wide basis is a complex
problem that should be attempted only by professionals.
The administration of community programs must be flexible.
This flexibility should, however, be based upon the established
principles of good mosquito management. A number of
techniques are available, depending upon the target species
involved and the priorities that have been established. For
example, the control of species involved as disease vectors
can be quite a different problem from that of species that are
strictly nuisance biters.
Health Education
All good public health programs must include education of
the public for understanding and support. This is especially
important with mosquitoes, because homeowners can help
greatly by managing their own property to eliminate mosquito
breeding sources. In areas where extensive breeding occurs
in containers on private property, the effectiveness of any
community-wide effort directed at public property alone will
be greatly reduced. It is, therefore, of utmost importance to
inform the citizens of the ways in which they can help.
Survey for Breeding Places
An effective community-wide mosquito management program
cannot be planned or conducted until a survey is made
to locate the major breeding places of problem mosquitoes.
This takes a great deal of time and work but is well worth
the effort. Though mosquitoes usually require standing water
for breeding, it is not true that mosquitoes will be produced
in every body of standing water. A survey will identify those
breeding sites that must be eliminated or treated. This will avoid
unnecessary environmental and monetary costs. Because
the most efficient management programs concentrate on the
control of mosquito larvae rather than adult mosquitoes, the
survey is an essential prerequisite.
Any site that accumulates standing water should be
examined for possible mosquito breeding. Visual inspection
of sites should be made, and mosquito larvae should be
sampled with “mosquito dippers” for species identification.
Sites identified as actively breeding mosquitoes should be
noted for follow-up control efforts.
Adult mosquito surveillance measures mosquitoes populations
that have successfully developed and emerged from
aquatic habitats. Use of light traps (e.g., New Jersey light
trap, CDC light trap) are standard tools for adult sampling.
Landing counts can also be used.
For training opportunities in mosquito surveillance
techniques and species identification, contact the
Indiana State Department of Health for available sessions.
Source Reduction and Habitat Alteration
Many mosquito problems can be permanently reduced by
either eliminating breeding places or altering the habitat in
such a way as to reduce the numbers of larvae that can be
supported. This might mean cleaning a shoreline of vegetation
that provides natural harborage for larvae. Eliminating
a source of organic pollution will alter a breeding place to
not only deprive larvae of nutrients, but also to provide an
environment in which mosquito predators can survive and
become established. Under no circumstances should a body
of water be drained or an area filled until permission has
been obtained from the local drainage board and until it has
definitely been established that problem species breed in it
in sufficient numbers to cause problems.
The following practices may be used to reduce mosquito
breeding sites.
1. Ditch and clean stagnant streams to insure a continuous
flow of water to eliminate border vegetation that
produces habitat for mosquito larvae to develop.
2. Drain or fill back-water pools and swamps where stagnant
water accumulates. Sanitary landfills can often be used
in such locations, resulting in the elimination of mosquito
breeding sites and improving the value of the land. Check
with the Indiana State Department of Health, however,
before establishing such landfills.
3. Because all mosquitoes breed in shallow quiet water,
remove vegetation and debris from along the shores of
lakes and ponds to discourage mosquito breeding. Such
bodies of water should have a steep clean shoreline with
as little vegetation as possible. Weed killers may be used
in some cases to eliminate or prevent emergent plant
growth. Refer to Purdue Extension Publication WS-21
“Aquatic Pest Management” for further information
on the use of aquatic herbicides.
4. Stock small lakes and ponds with top-feeding minnows
if allowable.
5. Improve wetlands and marshes to encourage development
of mosquito predators (e.g., frogs, predatory insects,
predatory fish).
CHEMICAL MANAGEMENT TECHNIQUES
The use of chemicals is, at best, a temporary expedient
that should be limited to only those situations for which no
other alternatives exist. In general, chemical control can be
divided into two major operations. The first, larviciding, is the
most efficient and effective, and should be the backbone of

3 MOSQUITO MANAGEMENT BY TRAINED PERSONNEL — E-52-W
any good chemical program. The second, adulticiding, is less
efficient and as such should be used strictly for supplemental
or emergency purposes. The detection of active transmission
of mosquito-borne disease is an example of such an
emergency. The Indiana State Department of Health routinely
monitors levels of arborvirus transmission throughout the
state and may be contacted for information on the status of
disease transmission.
A number of insecticides have been registered for use
in mosquito control. The relative value of chemical control
varies with the mosquito species and the location conditions
where control is to be applied. Because each situation differs,
care must be taken to select the proper insecticide for
a particular situation. Some of these factors include:
• Effectiveness against target species (resistance problems);
• Relative toxicity to humans and domestic animals (impact
on non-target organisms);
• Contamination of food, garden, or fruit;
• Cost;
• Availability in quantities needed;
• Need for residual action in some situations;
• Chemical stability;
• Flammability;
• Ease of preparation;
• Corrosiveness; and
• Offensive odor, staining, etc.
Resistance can be a problem in mosquito control,
especially when using organo-phosphate and pyrethroid
compounds. However, before assuming that resistance is
the cause of poor control, it must be established that poor
control is not caused by other factors such as improper identification
of mosquitoes, spray techniques, lack of knowledge
about insect habits, or faulty source reduction procedures.
Any decrease in susceptibility should be substantiated in
carefully controlled tests before seeking another toxicant or
considering a change of procedure.
PESTICIDE SAFETY MEASURES
The key to the safety of humans and other nontarget
organisms is knowledge of the hazards involved in handling
and applying pesticides.
All pesticides must be handled in such a way that any
possibility of harm to nontarget organisms (including humans),
either through contamination of food and water or by contact,
is kept to a minimum. Before using any pesticide it is essential
to first READ THE LABEL. In preparing and applying the
pesticide, FOLLOW ALL DIRECTIONS CAREFULLY.
• Wear protective clothing to avoid prolonged or dangerous
exposure to pesticides.
• Take care to avoid contamination of foods or drinking
water of human and animals.
• Keep application equipment clean and in good condition.
• Store pesticides only in their original containers with
the proper label and out of reach of children and animals.
• Dispose of empty containers properly, and know the
emergency measures for treating accidental poisoning
and cleaning up of spills or other pesticide contamination.
Many chemical insecticides registered for use in mosquito
control are toxic to birds, fish, and other wildlife, so appropriate
precautions must be taken. In addition, most of these
insecticides are toxic to bees exposed to direct treatment or
to residues on crops. In making applications, care should be
exercised to avoid getting any of these insecticides on food or
feed crop areas. Instructions on the label will give precautions
or restrictions while using insecticides for mosquito control.
LARVAL CONTROL
Mosquito breeding sites that are undesirable or impossible
to alter or eliminate may be treated with an appropriate
larvicide. Table 1 lists the insecticides recommended for use
as mosquito larvicides in Indiana. The application of larvicides
should only be made at sites where mosquito larvae of the
proper target species are present. In addition, the degree of
control obtained with larvicide applications often depends
upon the amount of pollution and the type and amount of
vegetative cover present. Some of the insecticides listed in
Table 1 thus have a range of application rates.
Where cover is heavy, granular formulations frequently
provide better control than emulsions or oil sprays. Repeated
treatments with some of these insecticides may be
needed, especially after heavy rainfall. Generally, three or
four treatments each season will be needed. For proper mixing
instructions, application rates, and precautions, all label
directions should be read and followed carefully. Application
rates may vary depending on the extent of vegetative cover
and/or degree of pollution of the water to be treated.
Granular larvicides can be applied from the air if the
plane does not have to fly over populated areas. Granules
can also be applied by crank-operated spreaders similar to
those used for spreading seeds and fertilizers. Knapsack
or other hand sprayers that can be carried by field workers
may be used for liquid formulations. Power sprayers may
be satisfactory if advantage is taken of the wind so that the
larvicide drifts into larval-infested water areas. Larvicide
treatment of fish-bearing waters should be avoided. Briquet,
granular, and pellet formulations are often preferred for use
in catch basins and in containers not easily disposed of.
ADULT CONTROL
Various application methods are available for adult mosquito
control. Thermal fogs can provide a rapid, temporary
control of adult mosquitoes with little residual effect. Thermal
fog generators break up the insecticide by means of hot
gases or superheated steam to produce a fog or smoke. This
method is effective only where there is little or no wind in the
evening or night. Malathion (Fyfanon) is recommended for
use with thermal fogging equipment.
A more effective method of ground application is the use
of ULV (ultra low volume) cold aerosol equipment. These
machines produce a very tiny droplet of high concentrate
insecticide, which results in a greater area coverage with
less dosage. This type of application is designed to kill active

MOSQUITO MANAGEMENT BY TRAINED PERSONNEL — E-52-W
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adult mosquitoes and provides little or no residual control.
Like the thermal fog generator, the cold aerosol machine
should be used during the time the adult mosquitoes are
most active. This means from twilight until about midnight,
when atmospheric conditions are usually best (lack of wind).
ULV application is generally the preferred space treatment
for adult mosquito control.
The cold aerosol method has certain advantages over
thermal fog generators. Less insecticide is applied, resulting
in fewer pollution problems. Smaller holding tanks and
consequently smaller vehicles are needed because smaller
quantities of insecticide are used. There is less of a traffic
hazard compared with thermal fog applications, which reduce
visibility. ULV ground applications, however, are somewhat
less effective than thermal fogs in heavy vegetation, because
the larger ULV droplets tend to be filtered out more rapidly.
Insecticides recommended for use with ULV ground equipment
include: permethrin (Biomist), chlorpyrifos (Dursban,
Mosquitomist), sumethrin (Anvil), malathion (Fyfanon),
synergized pyrethrins, and resmethrin (Scourge). (Note that
resmethrin is a restricted use insectcide.)
Application by fixed-wing aircraft or helicopter for adult
mosquito control is also a common practice. It is useful
under emergency conditions or if areas to be controlled are
too large or are inaccessible for economical treatment with
ground powered equipment. Best results are obtained in
areas without dense tree cover so that spray particles can
penetrate the low shrub zone where the greatest mosquito
activity occurs. To obtain uniform coverage of an area, careful
observance of preplanned flight patterns, altitudes, and air
speeds is essential.
Applications should not be made over a food or feed crop
area or populated areas unless the insecticide is labelled for
that use. Label directions regarding application over fishbearing
waters should be followed. The same insecticides
for use with ground ULV equipment can be considered for
aerial treatment. For proper mixing instructions, application
rates, and precautions for any insecticides used, all label
directions should be read and followed carefully.
READ AND FOLLOW ALL LABEL INSTRUCTIONS. THIS INCLUDES DIRECTIONS FOR USE, PRECAUTIONARY STATEMENTS (HAZ-
ARDS TO HUMANS, DOMESTIC ANIMALS, AND ENDANGERED SPECIES), ENVIRONMENTAL HAZARDS, RATES OF APPLICATION,
NUMBER OF APPLICATIONS, REENTRY INTERVALS, HARVEST RESTRICTIONS, STORAGE AND DISPOSAL, AND ANY SPECIFIC
WARNINGS AND/OR PRECAUTIONS FOR SAFE HANDLING OF THE PESTICIDE.
Revised 5/2010
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