ANR-999 IPM TACTICS FOR ARGENTINE ANT CONTROL
ANR-999, New Jan 1997. Faith
M. Oi, Extension Entomologist,
Assistant Professor, and David H. Oi, Affiliate Assistant
Professor, both in Entomolgy at Auburn University
IPM Tactics For
Argentine Ant Control
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The Argentine ant, Linepithema
humile (Mayr)--formerly named Iridomyrmex humilus--is
one of the more troublesome ants in Alabama. Argentine ants are
mainly a nuisance to people because they are often found indoors,
forming wide, noticeable lines or trails of ants into homes (Figure
1).
These ants do not sting or bite. They are 2-3 mm in length
and black to brown in color (Figure 2). Argentine ant workers
are all about the same size (monomorphic), in contrast to fire
ants, where workers can be different
sizes (polymorphic). Workers emit a faint musty odor when crushed.
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Figure 1. Noticeable lines or trails of ants. Arrow
denotes queen relative to worker ants. |
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Figure 2. Argentine ants feeding on sugar source.
Line depicts actual size of the ants. |
Colonies are large and can contain many queens. Nests can be
identified by the presence of brood. Brood are the larval and
pupal stages of the ant. Brood are cream colored to white and
immobile, so workers ants must carry them when they need to be
moved.
These ants probably arrived in Louisiana in the 1890s on coffee
ships from Brazil. They rapidly spread throughout the United States.
Entomologists have been trying to control these ants since the
early 1900s. Argentine ants avoid the cold winters by inhabiting
heated buildings.
Control Of Argentine Ants
Argentine ants are difficult to control for the following reasons.
- All ants are holometabolous (complete metamorphosis), having
an egg, larval, pupal, and adult stage. Foraging adult ants are
only a fraction of the total colony. Broadcast spraying around
the perimeter of the house targets only the foraging adult ants
in the colony. Control will be temporary since the colony will
simply send out more foraging ants when others are killed.
- The colony supports multiple queens if ant populations are
large. If a broadcast spray around the house is the primary method
of control, the Argentine ant workers and queens will scatter.
When the ants scatter in sufficient numbers, new colonies can
be formed. The one main colony can split into several smaller
ones, all of which have the potential to grow. Thus, broadcast
spraying alone can make the problem worse.
- Unlike many other ant species, Argentine ants from different
colonies do not fight. Therefore, their spread is less limited
because they are not territorial.
- Even with their large colony size, they are quite mobile
and can move from one area to another quickly. A broadcast spray
may temporarily alleviate an Argentine ant infestation. But there
is a good possibility that the ants will simply move to another
area until the chemical breaks down. After the chemical breaks
down, the ants will return because they are constantly scouting
and foraging for food, water, and nesting sites.
- Heavy mulch against the walls of houses creates pockets of
moisture that these ants need.
- Potted plants are a favorite nesting site. Moving infested
pots into the house can create an indoor infestation.
These characteristics combine to create a pest control nightmare.
Argentine ant control in the Southeast is an ongoing effort. Due
to the large size of the colonies and their rapid mobility, even
if one colony is eliminated, another will move into the area over
time.
IPM Control Program
An Integrated Pest Management (IPM) approach offers a greater
chance for control of the Argentine ant. An IPM approach incorporates
all available control methods into a pest management program.
IPM methods include identification, inspection, sanitation, exclusion,
and chemical strategies.
Identification
For maximum control make sure you properly identify the ant
pest. Different ants have different food preferences and different
behaviors that will directly impact the efficiency of ant pest
control.
Collection Tip--One way to collect ants for identification
is to place a dab of honey or sugar water in the center of an
index card. Place the index card where ants are seen. Allow ants
to recruit to the sugar source. Put ants on the index card into
a plastic bag, then place the bag in the freezer. The cold temperatures
will slow the ants down or kill them. When they are immobilized,
the ants can be easily tapped into a vial of alcohol and submitted
for identification.
Inspection
Find the source of the ants. Place bait or granules where the
ants are foraging or nesting. Generally, Argentine ant trails
will be conspicuous (Figure 1). If trails
are not obvious, placing an index card with a dab of honey or
sugar water where ants have been seen may help locate established
trails as ants recruit to the sugar source. In general, treatments
are not effective if they are not placed where ants are found.
Sanitation
- Eliminate sources of moisture (such as leaky faucets, plumbing,
and free-standing water) and food because these ants are scavengers.
- Clean windows of dead insects. These ants will feed on dead
insects.
- Remove the food source if ants are trailing to food. With
a mild detergent, wipe ant trails after food is removed to erase
the trail pheromone. The trail pheromone is a special chemical
that foraging ants lay down to guide other foraging ants to food
or to a new nesting place.
- Spray the ants with soapy water from a spray bottle. This
will often temporarily halt ant problems if insecticide use is
of concern around food or other sensitive areas. Soap breaks
the surface tension of the water, causing the ants to drown.
- Check potted plants for ants before bringing the plants indoors.
One way to check for ants is to water the soil thoroughly to
force ants out of the soil.
Physical Exclusion
- Caulk cracks and crevices in the house.
- Keep branches from coming in contact with your house (ants
will walk on them into the house).
Chemical
- Apply chemicals judiciously. Precision spot treatments at
points of entry into the house such as around window sills and
door thresholds may be effective. Broadcast spraying for these
ants is unwise. A liquid insecticide will make the area repellent
to ants. Ants will not feed on a bait that is placed in the vicinity
of a repellent liquid insecticide.
- Bait stations designed for outdoor and indoor use have been
reported to be effective in killing these ants. Look for products
with delayed toxicants such as hydramethylnon and sulfluramid.
The toxicant must be slow-acting because if ants die in the immediate
area of the bait, other ants will avoid the area and not feed
on the bait.
- 1 percent boric acid in a 10 percent sugar solution is a
homemade remedy for many sweet-loving ants such as the Argentine
ant. There are several disadvantages to this bait. First, it
is very slow-acting. Second, because the colonies are so large,
they must be given a constant supply, which means the homeowner
would have to repeatedly check on the bait. Even then, control
is not guaranteed. The only advantage is that this bait is inexpensive.
Characteristics Of The Ideal
Ant Bait
- Slow-Acting Toxicant
- Non-Repellent Toxicant
- Preferred Food Source
Baits work because they exploit the ants' behavior of sharing
food and nutrients with other ants. Passing nutrients from one
ant to another is called trophallaxis. If food contains a slow-acting
toxicant and the ant does not detect it, the toxicant is passed
throughout the colony by trophallaxis, before killing its members,
including the queen.
Ant baits work only if the ants eat the bait. Eliminate any
alternate food sources by keeping counters clean and storing food
in sealed containers.
Professional Pest Control
Good pest control operators have the training, equipment, and
materials necessary to perform ant control safely and effectively.
You may prefer to have all of your pest control done by a professional
because effective pest management requires extensive knowledge
of IPM tactics.
If you do contract the services of a pest control operator,
ask questions about the plan to control your pest problems and
get estimates from at least three reputable firms before choosing
one.
Trade names are used only to give specific
information. The Alabama Cooperative Extension System does not
endorse or guarantee any product and does not recommend one product
instead of another that might be similar.
For more information, contact your county Extension
office. Look in your telephone directory under your county's name
to find the number.
For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information.
Issued in furtherance of Cooperative Extension work in agriculture and
home economics, Acts of May 8 and June 30, 1914, and other related
acts, in cooperation with the U.S. Department of Agriculture. The Alabama
Cooperative Extension System (Alabama A&M University and Auburn
University) offers educational programs, materials, and equal
opportunity employment to all people without regard to race, color,
national origin, religion, sex, age, veteran status, or disability.
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