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Dangerous
Products and Promotions
That Have Limited Value for Mosquito Control
Wayne J. Crans, Associate Research Professor in Entomology
Virtually every year, a new product appears on the market that claims
to be the answer for the elimination of mosquito nuisance. In nearly every
case, the promotion is accompanied by a great deal of advertising, but
the merits of the product are rarely backed with scientific testing. The
American public has invested billions of dollars in zappers, repellers,
and plants that claim they will keep mosquitoes from biting. Products
and promotions for mosquito control are big business; unfortunately most
have limited value in reducing mosquito annoyance.
Electronic Repellers
Hand-held electronic devices that rely on high-frequency sound to repel
mosquitoes have become surprisingly popular in recent years. Prices range
from $9.95 to $29.95 for units advertised in magazines. Heavy-duty repellers
that claim to keep away spiders, hornets, and rats, in addition to mosquitoes
may sell for more than $100.00. The manufacturer's rationale for using
sound as a repelling factor varies from one device to the next. Some claim
to mimic the wing beat frequency of a male mosquito. This, supposedly,
repels females who have already mated and do not wish to be mated a second
time. Others claim to mimic the sound of a hungry dragonfly, causing mosquitoes
to flee the area to avoid becoming the predator's next meal. Most of the
electronic repellers on the market hum on a single frequency. Top of the
line devices allow for adjustment by the user to achieve the most effective
frequency for the mosquito causing the problem. Scientific studies have
repeatedly shown that electronic mosquito repellers do not prevent host
seeking mosquitoes from biting. In most cases, the claims made by distributors
border on fraud. Mated female mosquitoes do not flee from amorous males,
and mosquitoes do not vacate an area hunted by dragonflies. Electronic
mosquito repellers do little in the way of reducing mosquito annoyance.
Bug Zappers
Electrocuting devices, popularly known as Bug Zappers, are the most popular
device on the market for reducing mosquitoes around the home. Most rely
on ultraviolet light to draw insects through an electrified wire grid.
A resounding pop followed by a series of sizzling sounds signals the homeowner
that an insect has passed through the electrocuting device. Most homeowners
keep the machine on a timer that turns the units off during the daylight
hours, but some run the traps day and night during the summer season.
Bug zappers kill a lot of insects, but very few of the insects killed
function as pests. Most of the popping sounds are night-flying moths tricked
into the trap while attempting to navigate by the moon. The long drawn-out
sizzles are usually beetles, because they are heavier than most night
flying insects and have considerably more bulk to fry. Scientific studies
indicate that mosquitoes make up a very small percentage of bug zapper
collections. Comparison trapping has also shown no significant difference
in mosquito populations in yards with and without the traps. Biting insects,
in general, make up less than 1 percent of the insects killed in zappers.
Unfortunately, beneficial insects are usually well represented in an average
night's catch. The continued popularity of these traps is probably due
to the never-ending sound effects, which remind owners that their investment
is working. Most trap operators are unaware that their zappers are killing
harmless insects that would otherwise serve as food for wildlife.
Citrosa Plants
The Citrosa plant is a genetically engineered houseplant created by incorporating
tissue cultures of the grass that produces citronella oil into hybrid
varieties of geranium to produce a cultivar that emits a citronella aroma.
Citronella oil is known to have mosquito-repelling properties, and the
concept of allowing a plant to emit a barrier of repellent vapor appears
sound. Unfortunately, the claims made by the distributors have not stood
up to scientific testing. Tests conducted in Florida indicated that Citrosa
plants did not reduce the number of bites received by test subjects. Moreover,
mosquitoes landed freely on the leaves indicating that the plant does
not emit enough citronella oil to repel the insects. Crushing the leaf
and rubbing it into the skin did not keep mosquitoes from biting and mixing
the leaves into a slurry did not help. The idea of engineering a plant
with mosquito repelling properties should be encouraged. Advertising and
selling that plant before its effectiveness is documented takes advantage
of the American consumer.
Insectivorous Bats
Every so often, a well-meaning conservation group promotes bats to eliminate
mosquitoes from areas where nuisance has become intolerable. This undoubtedly
leads to rediscovery of research conducted in the 1950s indicating that
bats released in a room filled with mosquitoes could catch up to 10 mosquitoes
per minute. The research was conducted to measure the effectiveness of
echolocation in insectivorous bat species. The results have been extrapolated
to suggest that wild bats can consume 600 mosquitoes per hour. Using that
figure, a colony of 500 bats will remove 250,000 mosquitoes each hour
and theoretically afford mosquito control for an entire neighborhood.
Research since that time has shown that insectivorous bats are opportunistic
feeders and that mosquitoes make up a very small percentage of their natural
diet. Bats' behavior when locked in a room with nothing to feed upon but
mosquitoes has no bearing on their behavior in the wild. Bats feed on
the same insects that turn up in bug zappers and are no more effective
for controlling mosquitoes than their electronic equivalent. Providing
habitat to enhance bat populations is an admirable activity for conservation
purposes. Using mosquito control as the reason to initiate public interest
is misleading at best.
Purple Martins
The average person truly believes that Purple Martins control mosquitoes.
No other form of biological control has been so broadly publicized, and
the concept of using a colonial bird is easy to accept. Purple Martins
are lovely birds and having a colony nearby is educational and aesthetic.
Purple Martins, however, do not control mosquitoes and should not be propagated
if eliminating mosquitoes is the central issue. Proponents of the Purple
Martin cite the oft-quoted statement that a Purple Martin will eat 2,000
mosquitoes a day and up to 14,000 when the insects are extremely plentiful.
The quote is based on an anecdotal account in the literature that was
based on body weight of the bird and the number of mosquitoes that would
be required to sustain its metabolism. Most ornithologists realize that
mosquitoes form an insignificant portion of the Purple Martin's diet and
would agree that the birds play a limited role controlling mosquito populations.
If mosquitoes are plentiful, the birds will feed on them, but an adult
Purple Martin that is foraging in mosquito territory will accept a dragonfly
in place of a mosquito without hesitation. Purple Martins, as well as
other insectivorous birds, should be encouraged to nest and be provided
with housing whenever possible. Do not, however, believe that the birds
will significantly diminish mosquito populations in your community. The
manufacturers of Purple Martin houses cite mosquito control potential
for their own economic gains. The birds do not need this hoax to retain
public acceptance.
There are products on the market that will provide relief from mosquito
attack. Commercial repellents that contain DEET can be highly effective
for short periods. Many people, however, dislike the oily consistency
or object because of health concerns connected with the product. Products
that rely on fragrance to repel mosquitoes show considerable promise and
have been under intense investigation since the Avon product, Skin-So-Soft
showed proven repellent properties. Predacious fish feed on the immature
stages of mosquitoes and are extremely efficient in terms of control.
In salt marsh areas, native killifish can be managed to eliminate mosquitoes
from some types of marshland. In upland areas, pond-raised mosquito fish
can be stocked to eliminate mosquitoes. Electronic repellers, bug zappers,
and mosquito-fighting plants represent hoaxes that are marketed solely
for economic gain. The American consumer, should be aware that these products
have little value for mosquito control.
The author is indebted to Lee Mitchell of the Toledo Area Sanitary District
for much of the information included in this fact sheet.
New Jersey Mosquito Control Association, Inc. Contributed funds to help
defray the cost of this fact sheet.
NJAES Publication No. H-40101-01-96 supported by state funds.
Rutgers Cooperative Extension
N.J. Agricultural Experiment Station
Rutgers, The State University of New Jersey , New Brunswick
Distributed in cooperation with U.S. Department of Agriculture in furtherance
of the Acts of Congress of May 8 and June 30, 1914. Cooperative Extension
work in agriculture, home economics, and 4-H. Zane R. Helsel, director
of Extension. Rutgers Cooperative Extension provides information and educational
services to all people without regard to sex, race color, national origin,
disability or handicap, or age. Rutgers Cooperative Extension is an Equal
Opportunity Employer.
Taken from http://edis.ifas.ufl.edu/IN419
Table 1. Protection Times of Tested Mosquito Repellents
| Products
|
Active Ingredient
|
Average Complete Protection
Time
|
| AntiMos 301 |
Citronella; pine oil; garlic oil; dipentene oil;
comphor powder; camphene |
10 days |
| OFF! Deep Woods
|
23.8% DEET
|
5 hours
|
| Sawyer Controlled Release
|
20% DEET
|
4 hours
|
| OFF! Skintastic
|
6.65% DEET
|
2 hours
|
| Bite Blocker for Kids
|
2% Soybean Oil
|
1.5 hours
|
| OFF! Skintastic for Kids
|
4.75% DEET
|
1.5 hours
|
| Skin-So-Soft Bug Guard Plus
|
7.5% IR3535
|
23 minutes
|
| Natrapel
|
10% Citronella
|
20 minutes
|
| Herbal Armor
|
12% Citronella; 2.5% peppermint
oil; 2% cedar oil; 1% lemongrass oil; 0.05% geranium oil
|
19 minutes
|
| Green Ban for People
|
10% Citronella; 2% peppermint
oil
|
14 minutes
|
| Buzz Away
|
5% Citronella
|
14 minutes
|
| Skin-So-Soft Bug Guard
|
0.1% Citronella
|
10 minutes
|
| Skin-So-Soft Bath Oil
|
Active Ingredient not known
|
10 minutes
|
| Skin-So-Soft Moisturizing
Suncare
|
0.05% Citronella
|
3 minutes
|
| Gone Original Wristband
|
9.5% DEET
|
0
|
| Repello Wristband
|
9.5% DEET
|
0
|
| Gone Plus Repelling Wristband
|
25% Citronella
|
0
|
|