Part 1: Ants and Pesticides
Ants are a large nuisance in many households, warehouses, restaurants, and other structures. Their control
however can be hit or miss when not done exactly as should be prescribed. The effectiveness of pesticides in
ant control can be different with the use of repellant or non-repellant products. Products such as tempo and
other repellent pyrethroids can divide ant colonies, force ants into unwanted areas and trap ants in undesirable
areas of the home. When the long residual of a pyrethroid is desired it may be best to apply a bifenthrin spray
since befenthrin at a low label rate is repellent only to termites, and not to ants. The best solution for ants
however is a complex process that involves the use of more than just a simple "spray" to eliminate them.
For new account startup services and special one-time treatments, the use of a Fipronil based spray like
Termidor along the foundation is recommended, but several other products work well for that purpose. For
areas away from the foundation treatments may be done with a neonicotinoid based product. Neonicotinoid
products include the active ingredients Imidicloprid, Acetimiprid, and Thiamethoxam. A more advanced option
is the use of a liquid formulation with a dual mode of action. Generally, the ideal product would have a
pyrethroid, and a neonicotinoid active ingredient in the formulation. Products like Bithor SC, Transport Mikron,
Transport GHP, and Temprid SC have this type of dual action as recommended. At the lowest label rate these
products should not have a high enough repellency to effect control.
Outside dusts such as DeltaDust should be used in moderation, and not broadcasted so as to create an issue
with their repellency. In cases where their use may pose a threat to control they should not be used. There are
many types of granular ant baits used in lawns and gardens, but two primary types seem to work the best. The
first of which, boron based baits, are made by adding boric acid to ground corn, almonds, or other carrier
agents. These include Mother Earth Granules, Niban granules, and several other brands. Since they are
stomach poisons they must be eaten to cause insect death, and their mode of action makes it unlikely that
ingestion of the small amounts used would cause any harm to the environment or non-target pests. The
second type of granule includes abamectin based poisons that block the neurotransmitter gama aminobutyric
acid. Feeding and egg laying stops in insects, and death occurs after several days. These baits include
Advance 375a and Ascend granules. When used in sub lethal doses abamectin has been shown to limit
reproductive rates of ant queens.
Interior treatments are done in several different ways, with techniques and styles that are easily combined.
The first approach is liquid pesticide application. Liquid pesticides are best applied inside as a crack and
crevice treatment. Broadcast treatments are very unreliable, ill advised, and can be unsafe as well as
ineffective. On the contrary however crack and crevice treatments have a higher level of safety because of the
low amount of pesticide use, and can be more effective thanks to the precise nature of this type of application.
The targeted application of dusts and gel baits in addition to crack and crevice treatments ensures a higher
level of control. In some cases, the use of dusts and baits alone can be effective. Liquid treatments should be
used only when necessary. Baits can be used in areas along trails, but a good rule is to use them close to the
ground or an ant entry point. This will slow the ants climb up the walls, or into other areas making them less of
an eyesore. On the contrary however, ant bait place along ceilings will force ants to trail up walls and other
items to reach the bait.
Part 2: Types of ants
A.) One node ants: argentine and odorous
The center section of an ant’s body that separates the abdomen from the thorax is referred to as the pedicel.
The pedicel has either one or nodes that protrude from the top of it. Ants can be separated into two primary
types with other classifications grouping them into more complex sub groups. One node ants include several
species commonly encountered in pest control. Most structure infesting ants will have one node with the
exception of a few two node ant species. Argentine ants are the most common species found in southern
states and other states of moderate weather. They have large colonies that intermingle with other colonies on
the property allowing for the sharing resources. Control of these ants can be difficult because the large super
connected colonies will infest the inside of the house connected to several different queens outside with most
of the colony still out in the yard.
Argentine ant control should be well thought out before the treatment begins and the
property prepared with the customer's cooperation. Lawn watering should be
adjusted to alter the property in manner that lowers ant intrusion into the structure.
When a lawn is too wet ants can be pushed inside, when a lawn is too dry ants will
come inside land looking for water. As the seasons change lawn watering should be
adjusted to match. Likewise, the treatments should change throughout the year.
Ant populations are at their largest in the summer because ants reproduce most
heavily in the spring. When starting an ant service in the summer lowering the ant
population is the priority, but a treatment in the spring also involves limiting
reproduction rates. As argentine ants are killed by pesticides issues associated with their control arise from
their ability to quickly replace lost workers. Therefore, control in the months where their reproduction is high
can be greatly increased by the use of abamectin based baits outside. The opposite is true in the winter
however, ants do little foraging therefore they wouldn't take very much if any back to the nest, and if they did it
would have little effect since their rates of reproduction are lower.
As the seasons change argentine ants can be found in most areas outside, but the bulk of the population tends
to change locations with the changing weather. In the cold months argentine ants will move the colonies closer
to the structure, and as it starts to get warm ants move more out into the yard, and by summer most ants can
be found everywhere on a property from the house to the fence line. Over watering or under watering lawns
creates similar issues with too much water constantly forcing ants out of the ground, and not enough water
creates a need that must be met either by foraging from fountains, pools, leaking sprinklers, or even heading
inside of the home.
Argentine ants tend to be more of an outside pest therefore a majority of their control is done from outside.
Most of the colony will be outside of the house with a colony type that almost never moves a colony inside.
With the external nature of the colonies existence and only about three percent of the ant population ever
leaving the nest, the foundation treatment outside becomes a large part of their control and prevention.
Repellent products therefore are an ill-advised solution and outside baits become a very important piece to the
complete control plan.
Odorous house ants are closely related to argentine ants but their control is
much more complicated. They can and often do nest inside of walls, shiplap
ceilings and other interior areas. This makes their control very difficult since
the source of infestation is usually. Odorous house ant will also have colonies
with multiple queens and multiple satellite colonies. This behavioral trait
referred to as budding makes it even harder to control them since a lost queen
won't collapse the colony and lost workers are quickly replenished. Seeking
out and finding colonies whenever possible should be a priority when trying to
control or eradicate them.
Wall voids with a known or suspected colony can be treated with a foam machine and an appropriate non
repellent pesticide. Dusts should never be used for these ants because the dusts act repellent and force ants
into other areas of the structure. Likewise, repellent pesticides such as pyrethrum will also cause colonies to
move or divide. While the use of insect growth regulators seems appropriate, and would logically slow
budding, their use is not recommended. In fact, Nygard which would seem to be adequate, acts as a repellent
to odorous house ants, and in many cases causes more issues than it resolves. The best process for control
is the use of crack and treatments in infested areas, and localized gel bait placements.
Odorous house ants can easily be distinguished from other closely related ant species because of their potent
odor when crushed. The smell is said to resemble rotten coconut. Under a microscope more obvious visual
cues can be noted. They have the same globular anus as other closely related ant species, but the spiked
node on their abdomen is usually hidden against the thorax whereas it can be easily seen in the other closely
related species. They swarm with flying alates leaving the nest around the late spring. The swarmers do not
have the obvious smell when crushed therefore when looking at flying ants the smell cannot be used as a
factor for species determination.
B.) One Node Carpenter Ants:
Carpenter ants are a common type of ant that is divided into many different sub
species. Of those sub species only a few infest homes typically. Carpenter
ants typically live in trees where they create hollow cavities in wood to make
their nests and satellite colonies. These satellite colonies however can
sometimes be found in the structural and non-structural lumber of homes. A
key sign of infestation is the frass that can be found in areas of infestation.
Found among the wood shavings from the ant colony many times are ant heads
and other left over body parts. These parts are discarded from the colony and
can be easily distinguished from termite droppings which are smooth with evenly sized and exactly shaped
Carpenter ant workers are polymorphic which means that they can be found in different sizes. This is helpful
when trying to identify them, especially when you see more than one. Likewise, they have a globular anus,
which separates them from several other species of ant, and under a microscope a ring of yellow hairs can be
noted at the end of their abdomen. They have no stingers but in many cases are large enough to bite.
Their control inside of a house may involve injecting galleries where satellite colonies are located, treating the
outside perimeter, outside trees, and locally treating inside hot spots. Several companies make granular
carpenter ant baits for outside use, and liquid treatments can be done using appropriate non repellents.
Integrated pest management practices include the trimming of trees that are touching the house, and removing
dead trees from the property. These control measures are a necessity in many cases and can be the
difference between long term control and small, even unnoticeable changes.
Velvety tree ants are becoming more common in urban environments, in contrast with their situation a few
years ago. They traditionally were found in rural places and were not a typical problem within structures. They
do not prefer the inside of a house. In fact, most inside infestations clear up on their own without any
treatment. Outside they can be found under bark mulch, all over trees, and in dead logs. When crushed they
have a similar odor to odorous house ants. Their bodies have an obvious change in color between the
abdomen and thorax with the pedicel usually an orange color. The abdomen itself has small hairs on top that
resemble velvet which is why it has the name that it does. The abdomen therefore has a velvety appearance.
Treatments should not just focus on the ants themselves but should include the use of systemic insecticides
that kill honeydew producing insects since they are the primary food source of this species. Products with a
dual mode of action such as Temprid or Bithor are most appropriate and with cases such as heavy bark mulch
these products can be broadcasted with the use of power sprayer. The Temprid label allows for its use at a
rate lower than what is listed, and cutting it down to a rate of. 375% which is 4 ml per gallon is appropriate.
Because the treatment involves soaking the area, when the water evaporates a similar amount of pesticide will
be left on the ground as if the area were treated using a backpack sprayer at a higher rate. However, the
treatment will penetrate deep into areas of mulch, and ground cover as a result of the heavy spray and large
amount of water used by comparison. Abamectin based baits, and boron based baits make the job complete
when applying them outside as needed.
C.) 2 Node Fire Ants and Harvester Ants.
Many of the ant species with two nodes have similar characteristics. In the
case of many species such as fire ants and harvester ants they prefer to be
outside. In rare cases with fire ants, colonies and reproductives can be found
inside of wall voids with accumulated water, flooded basements, and areas of
water damage. In many cases roof leaks, and damaged plumbing are
discovered after a swarm of ants flies from the area.
Their control outside is done by treating mounds individually then applying a
general perimeter spray, followed by the application of baits. While many
companies make special fire ant baits, Advance 375a and other abamectin
based baits, or the full size Niban granules and their generics are appropriate.
The granules of Niban FG are generally considered too small for these larger ants with the exception of
Southern Fire Ants which are smaller, and a few other species that feed on smaller granules.
Fire ant workers usually have two rounded nodes on their pedicel, and they have stingers. The Red Imported
Fire Ant is red as the name suggests and very large compared to other ant species. The southern fire ant is
much smaller with the head and thorax red to brown and the abdomen mostly black. Harvester ants are red
like Imported Fire Ants, and also large, but can be easily be distinguished from them by noting the hairs on the
underside of the ant workers faces. These small hairs are the key defining characteristic of harvester ants.
D.) 2 Node Pharaoh Ants.
Pharaoh ants are a lot like odorous house ants with how they are controlled, but
aren't as easily moved from place to place. They are also much smaller than
most other ant species with a relatively small size of around 2mm in length.
They have stingers but don't use them. Budding is normal with this species and
they can have several hundred reproductives per colony, but growth regulators
can and should be used on them to limit reproduction. Pharaoh ants can nest in
walls and prefer to nest especially close to water sources. Areas behind
baseboards in bathrooms where humidity might make an area attractive are common nest locations, but also,
in wall voids, and even inside of furniture. Inside of houses they prefer warm humid conditions (80-86 degrees,
and 80% humidity).
Like with Odorous house ants the use of repellent pesticides increases the likelihood of treatment failure.
Treatments should always be done with non-repellent pesticides, and selective applications of baits, and dusts.
Repellent pesticides can force ants to go into hiding while colonies are moved, and return as a much larger
colony, or even multiply colonies in reaction to the repellency. Exterior treatments should not be overlooked
either, and should be done in many cases. These ants can nest outside close to the house, and can
sometimes be found under weed covers with workers foraging the adjacent rooms.
Part 3: IPM strategies for ants.
First and foremost, ant behavior varies depending on moisture. Overwatered lawns and under watered lawns
are of concern for many species of ants. Leaking pipes, roof leaks, and any moisture related structural defect
can lead to problems relating to any ant species. Proper lawn watering is very important. However, in many
cases homeowners prefer the simple, incorrect idea of "the more water the better." This often times forces ant
colonies close to the foundation, or inside of the house. Water is such an offense to ants that in many cases
ants can be seen carrying eggs as they leave an area just saturated. Ants will quite often enter homes as a
result of overwatering outside, but likewise a lawn that is too dry will also force ants inside. It is often seen on
the driest days of the year when ants scour the inside of a structure in search of what's missing outside; water.
Gaps and cracks that can provide ant entry should be sealed when possible. While weep holes around
windows should treated with an appropriate pesticide product, other cracks and gaps around window frames
can be sealed with appropriate caulking. Cracks in brick and concrete can be treated but for long term control
those gaps and cracks should be sealed. On the inside of a structure, countertops should be sealed along
joints, and gaps, with particular attention around sinks and toilets for areas that water or other wetness may
Particular attention should be paid to any recurring issue that ants seem attracted to. If an ant problem
continues with ants returning to a dripping faucet, or continuous food source such as dishes in the sink, those
conducive conditions should be corrected immediately. Care should be taken on all ant inspections to find
these issues that should be corrected. Dripping sprinklers, spilled food in cupboards, loose candy stashes and
many other things can contribute to an ongoing ant infestation. In many houses things fall behind refrigerators,
stoves, and other items that do not get moved regularly. Checking, and cleaning these areas are always a
necessity. Treating these areas may also be appropriate, but not always necessary.
Photos courtesy of photographers published on Bugwood.org ITP Node
The use of trade names in this publication is solely for the purpose of providing specific information. American Pest CEUS does not
guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of
other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use
pesticides safely. Read and follow directions on the manufacturer's label.