Fire Ant Control: Feasibility Study
former technical writing student
now with the Texas Department of Health
Plans to develop a commercial campground on a 10-acre
plot in western Bastrop County are contingent on
establishing a fire ant control program to allow people
and domestic animals to use the land for recreational
This report describes the current fire ant problem
on the property, lists the criteria set by the potential
developer, gives the reasons for a limitation of the study
to a comparison of broadcast treatments, compares two fire
ant control programs, outlines conclusions based on the
comparisons, and offers recommendations.
Note: See the technical review of this report.
Current Fire Ant Infestation Levels
Fire ant infestation rates on the 10-acre property
average 80 visible mounds per acre. In the most heavily
infested areas, more than 100 mounds per acre are visible.
Since mounds are not visible during the first 30 days of the
development of the colony
, the total infestation rate
should be assessed at a level higher than the visible mounds
suggest. Without treatment, the infestation can be expected
to increase. At current levels, development as a campground
is not feasible.
Fire Ant Control Criteria
Criteria for the fire ant control program are based on
the needs of the potential developer. The goal of the study
is to identify a program that will:
- Reduce fire ant population by 90% or more.
- Maintain fire ant population at a level appropriate for
safe, continuous use of camping facilities from April
- Maintain environmental toxicity levels well below those
allowing recreational use of the property.
- Minimize costs.
- Minimize frequency of product application.
Limitations of the Study
Two types of fire ant control treatments are available:
individual mound treatments and broadcast treatments. The
most common treatments for individual mounds include
chemical drenches, surface dusts, injected toxicants,
fumigants, and baits
[11:20]. Broadcast treatments are baits
composed of corn grits coated with soybean oil and a
toxicant. With the exception of bait, treatments for
individual mounds are fast-acting pesticides designed to
kill high numbers of fire ants
[12:144]. Since the only way
to destroy a fire ant colony is to kill the queen
individual mound treatments often fail because they do not
affect the queen. Although thousands of ants may be killed,
the queen is whisked to safety deep in the mount. A queen
can lay up to 1,500 eggs a day
repopulate the colony or she can simply move to a new
location and establish a new colony. Another disadvantage of
individual mount treatments, including bait products used to
treat individual mound, is that developing colonies are not
visible and, therefore, may not be treated
addition, locating the mounds takes more time than
broadcasting a product over the entire area.
Given the shortcomings of individual mound treatments,
this study is limited to a comparison of the two existing
types of broadcast treatments, most commonly marketed as
Amdro and Logic. These bait products are based on
theknowledge that both the larval stage and adult ant stores
liquid food and regurgitates it to feed other ants,
including the queen. The baits include slow-acting chemical
agents which are passed along until they reach the queen and
kill her to eradicate the colony.
Comparison of Fire Ant Broadcast Treatments
Amdro and Logic represent different types of fire ant
broadcast treatments. The two products will be compared on
the basis of the following factors:
Chemical actions of Amdro and Logic.
ingredient in Amdro, tetrahydro-5,5-dimethyl-2(1H)-
methyl)phenyl)-2- propenylidene)hydrazone, is an insecticide
that is activated slowly to allow time for it to reach the
[8:122]. The active ingredient in Logic is fenoxycarb,
a growth regulator, that, when consumed by the queen,
prevents her from laying eggs that normally would develop
into worker ants. As the number of worker ants diminishes by
natural death and no new workers take the place of the dead
ants, the queen dies from lack of care and feeding
Logic also affects eggs that would normally develop into
themales which swarm and mate to produce new queens. These
swarmers are born with deformed wings, preventing them from
swarming and mating
. Both Amdro and Logic are designed
to eradicate a fire ant colony by killing the queen, but do
so by different chemical actions. Amdro kills the queen with
a poison; Logic inhibits normal ant development.
- Chemical actions
- Application requirements
- Environmental hazards
Application requirements of Amdro and Logic.
treatments should be applied when ants are active and the
ground temperature is between 7005 and 9505 F. The ground
must be dry, with no rain forecast for the next few hours
Amdro is designed for broadcast application on
pastures, range grass, lawns, turf, and noncrop areas
at a rate of 1 to 1-1/2 pounds per acre
. It may
also be distributed around the base of an individual mound
at a rate of 5 tablespoons per mound, not to exceed a total
of 1-1/2 pounds per acre, including any bait broadcast in
Logic is recommended for controlling fire ants around
homes, office buildings, city utilities, on roadsides, in
parks, cemeteries, school yards, and on golf courses at a
rate of 1 to 1-1/2 pounds per acre. For best results, both
mound and broadcast treatment are recommended
application rates of Amdro and Logic are the same. Both
products are designed primarily as boardcast treatments on
turf but individual mount treatment is recommended in
conjunction with the broadcast method.
Environmental hazards of Amdro and Logic.
hazards can be assessed on the basis of toxicity of the
product, the range of organisms affected, and product
accumulation in the environment.
The toxicity of a substance is generally
expressed in terms of its lethal dosage, the amount of the
substance which, when ingested, results in the death of 50%
of the test animals
. Lethal dosage is abbreviated as
LD50. The lower the LD50 number, the more toxic the
. The LD50 is 1131 mg per kg of body weight for
the active ingredient in Amdro
[8:122]. The LD50 of the
active ingredient in Logic is 9220 me per kg of body weight
The active ingredient in Amdro is approximately
eight times more toxic than that of Logic. However, a lethal
dosage ratio of 1131 (Amdro) to 8813 (Logic) more accurately
compares the difference in toxicity between the two products
because Amdro contains 0.88% active ingredient and Logic
contains 1% active ingredient. As purchased, the commercial
product Amdro is approximately seven times more toxic than
In practical terms, a lethal dosage for a medium-sized
dog (weighing approximately 35 pounds) is more than 3 pounds
of the active ingredient of Amdro. Since a one pound bag of
the product contains only 1% active ingredient, the entire
amount of Amdro purchased to treat a 10-acre camp ground
would not constitute a lethal dosage for a medium-sized
animal. Smaller animals are in greater danger of ingesting a
lethal dosage. However, non-fatal health effects, such as
diarrhea, can result for any size animal from consumption of
a tablespoon of Amdro
. Logic, by virtue of its lower
toxicity level, would need to be consumed at a much higher
rate to produce comparable effects.
- Organisms affected.
In addition to killing fire ants,
Amdro kills harvester ants. At a higher concentration, the
active ingredient in Amdro kills cockroaches. Amdro may
attract pets and rodents
[8:123] and, if consumed in
sufficient amounts, can kill pets. Amdro is toxic to fish
. When used as recommended, Logic affects only ants,
including harvester ants and other ant species that compete
with fire ants. Since it has the same corn grit and soybean
oil base as Amdro, it is attractive to pets and rodents
but must be consumed in greater amounts to be fatal, due to
its lower toxicity. Logic is also toxic to fish.
- Environmental accumulation.
Amdro does not accumulate
in the environment and is not systemic in plants
Logic dissipates rapidly in soil. No residues can be
detected three days after application
product remains toxic for an extended period of time in the
Effectiveness of Amdro and Logic.
The initial effects
of Amdro are noticeable 1 to 2 weeks after application and
theproduct reaches maximum effectiveness in 1 to 1-1/2
. In a study conducted by Texas Department of
Agriculture (TDA) personnel
[9:2-3], 8 weeks after a single
broadcast application of Amdro on 4 test plots, the number
of fire ants and colonies had been reduced by 88% and the
toal ant population by 92%. After 35 weeks, 86% fewer
colonies existed, compared to pretreatment levels. Ant
population had been reduced by 98%. One year and 13 days
after the Amdro application, the number of mounds on the
test plots ranged from 47% fewer than pretreatment level to
32% more than that level. Population reduction averaged 35%.
Initial effects of Logic are not apparent until 2 to 3
months after application
. In the TDA study
of the fire ant colonies had been eradicated and the ant
population had been reduced by 92% at 8 weeks after a
broadcast treatment of Logic. At 35 weeks, Logic-treated
plots averaged an 81% reduction in the number of fire ant
colonies and a 98% reduction in fire ant population. One
year and 13 days after the application of Logic, levels of
mound reduction ranged from 91% to 46%, depending on the
plot. Ant population reduction was 87%. Table 1 is a
summary of the results of the study.
|Table 1. Table of fire ant mound and population reduction
rates for a single application of Amdro and Logic.
||1 Year, 13 Days
Early spring application (as soon as soil temperatures
reach acceptable levels) of Amdro would bring fire ant
population levels into the range desirable for recreational
use of the 10 acre property in 8 weeks or less. An
additional fall application of Amdro would be required to
maintain acceptable fire ant population levels. Early spring
application of Logic would bring fire ant population levels
under control in 8 weeks. A single annual application in
early Spring would maintain desirable fire ant population
Both Amdro and Logic have a com grit and soybean
and must be used within three months after
opening to be effective
. Baits are available in large 25
pound and 50 pound quantities for a low price per pound but,
for the purposes of this study, large purchases are not cost
effective due to the short life of the open product. For the
purpose of treatment of the 10-acre property, purchases of
quantities of 15 pounds or less are appropriate. Therefore,
this cost survey is limited to retail prices of small
quantities. Only the lowest prices are reported, excluding
taxes. A 1-pound container of Amdro costs $7.99 at HEB
grocery stores. At application rates of 1 pound per acre,
broadcast twice a year, the cost is $159.80 per year. At
application rates of 1-1/2 pounds per acre, the annual cost
is $239.70. B&G Company sells 4-pound bags of Logic for
$28.79. At application rates of 1 pound per acre, the annual
cost of Logic is $86.37. At rates of 1-1/2 pounds per acre,
the annual cost is $115.16.
Product costs for Logic are significantly lower than
costs for Amdro. Additionally, only one annual application
of Logic is required, compared to two aplications of Amdro,
so labor costs for Logic are half those of Amdro.
From a business perspective, the comfort and safety of
campers are probably the most important factors in the
consideration of fire ant control measures. If campers are
not relatively free from ant bites (most people expect a
few--this IS Texas) and protected from harsh chemicals, they
will not return to the campground or recommend it to friends
and family. Once comfort and safety are achieved, cost
effectiveness becomes an important factor. The following
conclusions can be drawn from the preceding comparison of
chemical action, application requirements, environmental
hazards, product effectiveness, and cost of Amdro and Logic:
A factual summary of these conclusions is presented in
- Amdro and Logic have identical application requirements
- Amdro is approximately 7 times more toxic than Logic.
Neither product accumulates significantly in the
environment. At recommended application rates, neither
product poses a serious threat to people or pets.
- Amdro acts more quickly than Logic, but Logic has better
long-term control capabilities. One annual spring
application of Logic maintains approximately the same
level of fire ant control as two applications of Amdro
- The annual product cost for application of Logic at a
rate of 1 pound per acre is 47% lower than the cost of
Amdro appliced at the same time. At rate of 1-1/2 pounds
per acre, the cost of Logic is 53% lower than the cost of
- Labor costs for Logic application are half those of
|Table 2. Factual Summary of Comparisons of Amdro and Logic.
|Application rates in pounds/acre
||1 - 1.5
||1 - 1.5
|Lethal dosage of active ingredient in mg per kg
||1 to 2 weeks
||2 to 3 months
|Duration of effects at desirable levels
|Number of annual applications
|Annual product costs
||$86.37 - 115.16
To achieve long term fire ant control on the proposed
campground, a single annual application of Logic in the
early spring is recommended as the most effective, least
toxic, and most cost-effective long-term method. However,
since spring has already passed, I recommend a broadcast
treatment with Amdro now to control fire ants immediately
and allow development of the campground. If the property can
be treated with Amdro and left undisturbed for 6 to 8 weeks,
the fire ant population should be brought to and maintained
at a level allowing recreational use of the property for the
remainder of this year's camping season. A single
application of Logic early next spring and each subsequent
spring should maintain the level of fire ant infestation
within the desired level for the proposed use of the
- Amdro Fire Ant Insecticide. Produce label. Wayne, NJ.:
American Cyanamid Co., 1987.
- Clair, Dan. Pest Management Program, Texas Department
of Agriculture. Personal interview, Austin, TX. June 26,
- Logic Fire Ant Bait, Technical Data. Commercial
- Logic Professional Fire Ant Bait. Product label.
Memphis: Terminix International Inc., n.d.
- Mulder, Roger. Pest Management Program, Texas Department
of Agriculture. Personal interview, Austin, TX. June 14,
- Rhodes, T. C. DVM. Personal interview, Cedar Creek, TX.
June 16, 1989.
- Texas Department of Agriculture, How to Safely and
Successfully Manage Fire Ants (without resorting to the
use of harsh chemicals). Austin, TX. n.d.
- Thomson, W.T. Agricultural Chemicals: Book 1,
Insecticides. Fresno, CA: Thomson Publications, 1985.
- Trostle, Mark R. "Ground Application of Bait Toxicants
to Texas Sod Farms." Paper presented at the 1989
Imported Fire Ant Conference, Biloxi, MS.
- United States Environmental Protection Agency. Pesticide
Fact Sheet, No. 78. Washington, DC: February, 1986.
- Vinson, S. Bradleigh, and A. Ann Sorenson. Imported Fire
Ants: Life History and Impact. Department of Entomology,
Texas A&M University, College Station, Texas, and
Agricultural & Environmental Sciences, Texas Department
of Agriculture, 1986.
- Yoffee, Emily. "The Fire Ant: Ruthless, Dangerous,
Unstoppable - and It's After You." Texas Monthly,
August, 1988: 80-85 and 142-146.
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