Ant Baits

Ant Trails: A Key to Management with Baits1
John Klotz, Dave Williams, Byron Reid, Karen Vail, and Phil Koehler2

1. This document is ENY-259, one of a series of the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences, University of Florida. First printed: March 1994. Revised: September 2000. Reviewed: August 2003. Please visit the EDIS Website
at http://edis.ifas.ufl.edu.
2. John Klotz, Dave Williams, USDA-ARS, Insects Affecting Man and Animals Labroatory, Gainesville, FL; Byron Reid, Bayer Corporation; Karen Vail,
associate professor, Department of Entomology and Plant Pathology, University of Tennessee, and Phil Koehler, professor/extension entomologist,
Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville,
32611.

The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational
information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.
For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative
Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean.

Communication in the ants is based on chemical signals.

These chemicals are called pheromones and
vary from alarm and nestmate recognition, to the one
we will focus on here, recruitment. All of the pest
ants use odor trails for orientation, but these trails
differ from one species to another. Where the
pheromones originate in the ant's body, their
chemical composition, as well as how long they last,
all vary from one ant species to the next. In fire ants,
the trail chemical is produced by the Dufour's gland,
which is named after its discoverer, Dufour, and is
laid down by the stinger. This pheromone is made up
of molecules which evaporate very quickly. Thus, the
fire ant's odor trail is very short-lived. In comparison,
the trail pheromones of some carpenter ant species,
which are produced by the hind gut, will last for days.
However, in both cases, these odor trails have the
same purpose of communication, namely recruitment
to a resource.

Trailing
A scout ant in search of food leaves the nest and,
in the random search pattern that follows, takes a
somewhat meandering path outward, until she finds
food. She then feeds on the food source and heads
straight back to the nest (Figure 1). Somehow on the
outgoing trip she can keep track of her position with
respect to her nest, and, on the return trip, uses this
information to take the shorter, more direct route
home. On the way back to the nest, she lays down an
odor trail. Once back in the nest, this scout ant then
alerts her nestmates of the food find, which
encourages them to leave the nest. These recruited
ants will follow the odor trail directly to the food
source. In turn, each ant will reinforce the odor trail
until the food is gone. This behavior is a highly
efficient means of exploiting a temporary food
resource.

Figure 1. Ant trail. Credits:
Ant Trails: A Key to Management with Baits 2
In some instances, these odor trails can become
more or less permanent, as in the case of ants that are
visiting permanent food sources such as an aphid
colony, garbage area, and other sites in structures
with permanent food and water. The trail can even be
physically cut into the turf, as with carpenter ants that
chew their way through the thatch layer.
Structural guidelines are another type of trail
that ants use to orient in their natural environment.
These may include twigs and branches which ants use
to travel to and from the nest on foraging trips.
Traveling along a branch lying on the forest floor is
much quicker than negotiating a path through grass or
leaf litter. In the man-made structural environment,
guidelines consist of pipes, conduits, wires and other
utility lines. Ants follow these guidelines to enter
structures as well as to travel within them. These
structural guidelines serve as natural highways for
ants.

Trailing along these chemical or structural
guidelines is an important behavior of ants that if
better understood can be exploited for control
purposes. In inspections, trailing ants should be
observed carefully to determine where they are
getting into structures. Through close observation, the
source of the infestation can be located. Following
trailing ants is the best way to locate the actual nest
site. One can feed wandering ants a little honey or
pieces of insects and then follow them directly back
to their nest site.

In the two examples which follow, this
behavioral knowledge will be applied to the control of
Pharaoh ants in an apartment complex, and carpenter
ants in a home.

Pharaoh Ants
Perhaps never is it more critical to consider
trailing behavior than in baiting programs for
Pharaoh ants (Figure 2). Baits cannot be placed in
just any location and be expected to work. Pharaoh
ant trails and their resources (both food and water)
must be located for proper placement of baits and
effective control.

Figure 2. Pharaoh ant. Credits: James Castner, University
of Florida

An interview with each apartment dweller is a
good way to begin to locate areas of ant activity, and
to educate the resident on the control program. It is
important for the resident to understand that it will
take time for the bait to eliminate the ant problem.
The resident should understand that delayed-action
baits take time to accumulate a toxic dose in the ant
colony, so that the entire colony can be eliminated.
Sprays may be used several days later after baits are
applied to kill off any stragglers, but sprays should be
avoided initially as they will only cause satelliting
(formation of new nests), will kill only a few
foragers, and might contaminate bait stations.
A pretreatment survey should be conducted first
using a dab of peanut butter on a white index card.
The cards are then placed where food and water are
located throughout the apartment complex as well as
outside. Inside, survey cards should be placed in the
apartments, and other areas such as the lobby,
kitchens, laundries, lounge areas and offices. At least
eight to sixteen cards should be placed in each
apartment (usually two to four each in the kitchen,
living room, bathroom, and bedroom). Survey cards
should be placed in any areas where the resident has
seen ant activity.

Window sills should be used for card locations in
the living room and bedroom of each apartment. Dead
insects on window sills attract foraging ants, and the
numerous cracks and crevices around window casings
are ideal nest sites. In the kitchen and bathroom,
cards should be placed near sources of water, such as
pipes and drains, sinks, counter tops, and toilets.
Outside, survey cards should be placed near windows,
around entrances and exits, and incomming and
outgoing plumbing lines. It's important to position
the cards along edges or other structural guidelines,
where the ants are likely to travel. These cards should
be left undisturbed for several hours, and then the
number of worker ants on each card should then be
estimated and recorded on an inspection diagram.
Ant Trails: A Key to Management with Baits 3
This pretreatment survey locates areas where ant
activity is concentrated, so that baits are put out in
areas of greatest ant activity. Monitoring will find
small isolated colonies that otherwise might be
overlooked and could cause reinfestation in the
future. Where feeding occurs at survey cards, the
trailing ants should be traced back to where they are
entering from a crack or crevice, switch plate, pipe
flange, etc. These entrance sites should be noted on
the diagram, and the toxic baits placed here in the
treatment program.

A good floor plan of an infested apartment
complex can be used as the inspection diagram to
document survey data and locate bait treatments. Not
only is this an invaluable tool, but it can also be used
to educate the resident about the ants and discuss
treatment strategy. A floor plan will help in
estimating how much bait or how many bait stations
to use. For an average size room, four to six bait
stations (depending on the level of infestation),
should be sufficient. A large apartment complex with
a heavy infestation of Pharaoh ants will require more
bait and application time, as well as the potential for
a higher frequency of reinfestation compared to a
small apartment complex with a light, localized
infestation.

Carpenter Ants
Although baits are available, the primary
methods for carpenter ant (Figure 3) control are nest
and barrier treatments with residual insecticides. How
can knowledge of trailing behavior be applied to
these methods of control?

Figure 3. Florida carpenter ant. Credits: James Castner,
University of Florida
In carpenter ant control, probably more so than
with most other ant problems, the pretreatment
inspection survey is the single most important
component of a successful control program, because
the nest site is very often extremely difficult to find.
Here, again, the use of structural guidelines by
carpenter ants should be emphasized for inspections.
In cases where control measures have failed it may be
helpful to conduct a night inspection, since carpenter
ants are nocturnal. Just as in Pharaoh ants, a
pretreatment survey (using insects or honey instead of
peanut butter) may also help in determining areas of
ant activity.

The treatment should be focused on areas where
ants travel: behind pipe flanges and switch boxes
where the ants travel along pipes or wires in wall
voids. For treatment inside structures use dusts
applied lightly to avoid repellency which occurs
when too much dust is present. The ants must walk
through the dust and pick it up, not walk around it.
On the outside perimeter, liquid sprays are
applied in a band that is thoroughly and judiciously
placed to prevent ants from trailing into a structure. If
this is not carefully done to provide a continuous
barrier, ants will find a break or bridge to cross over
and infest our structures.

Besides these important chemical control
procedures, there are several nonchemical techniques
which can be used to help out. Trimming back
vegetation that may provide runways for the ants onto
the structure and sealing or caulking entryways into a
structure.

In dealing with ants always keep one step ahead
of their trails, whether during inspections to
determine how they are getting into the structure and
where they are traveling within a structure, or during
treatment focusing on those areas where ants are
likely to travel. Incorporating these ideas on trailing
behavior into ant control programs will insure more
effective inspections and more successful treatments,
and allows for better control while minimizing the
use of chemical pesticides.
Ant Trails: A Key to Management with Baits 4
Using Bait Stations
Like all living organisms, ants have certain
nutritional requirements: carbohydrates, proteins, and
fats. In nature they obtain these essential nutrients
from a varied diet of insect prey (proteins and fats),
nectar, aphid honeydew and other plant products
(carbohydrates). These nutrients are found either in
liquid or solid form. Ants naturally strive for a
balanced diet to optimize the growth of the colony,
however, the amount of each of these three dietary
requirements necessary for optimal growth may vary
seasonally. For example, "bait switching" is well
documented in Pharaoh ants which have satisfied
their appetite for one food and then consequently,
they choose another. Carpenter ants eat a diet rich in
proteins during brood development, usually in the
spring and summer, but the colony will change to
carbohydrate foraging in late summer and fall to meet
the adult worker's increased energy requirements
(Figure 4).

Figure 4. Dietary traits of carpenter ants. Credits:
As structural pests, the ants' opportunity to
achieve a balanced diet is limited only by sanitation
practices and the baits used to control them. Ideally,
sanitation problems can be corrected, so that baits
don't have to compete with other food items, thus
forcing the ants to feed on whichever bait is provided.
Baits are more target-specific than broadcast
applications of insecticides in spot and perimeter
treatments that place heavy loads of broad-spectrum
insecticides into the environment. Baits are more cost
effective compared to more labor intensive
inspections to locate nests (attempts which are often
unsuccessful) and to treatment strategies which often
involve invasive techniques like drilling and dusting.
And, if baits are used properly they are highly
effective. For example they exploit the natural
foraging behavior of ants to recruit and share
resources, thereby spreading the bait toxicant
throughout the entire colony, and eventually
destroying it.

On the negative side, baits tend to be slower
acting than sprays or dusts, requiring patience by a
distraught resident, for example, who needs to be
educated on how baits work and the length of time
required to gain control. Also, their shelf-life is
limited due to susceptibility of the attractive part of
the bait to spoilage. However, the many advantages
of baits far outweigh these two disadvantages, which
can be alleviated through education of the resident
and new and improved bait formulation.
A bait consists of four components: (1) an
attractant, usually a food or pheromone which makes
the bait acceptable and readily picked up, (2) a
palatable carrier, which gives the physical structure
or matrix to the bait, (3) a toxicant, which should be
non-repellent, and delayed in action, effective over at
least a ten-fold dosage range, and (4) other materials
added for reasons of formulation, such as emulsifiers,
preservatives, waterproofing or antimicrobial agents.
Each of these components must be developed and
tested for efficacy. Currently, a variety of baits can be
selected, whose efficacy range from marginal to
excellent in control.
So, how does one deal with this bewildering
array of baits?

The best test of a bait is how it works in the field.
If the ants are attracted to the bait and are feeding,
there's a good chance of eliminating the problem.
However, this only holds true if the bait contains a
toxicant that is slow-acting. Fast-acting insecticides
are only going to kill foraging ants, allowing the
queen, nest workers, and brood to survive and soon
replace those few that are killed before sharing the
poison with their nest mates. Slow-acting insecticides
allow time for the foragers to exchange food,
eventually eliminating the entire nest when the
toxicants reach lethal levels.

Ant Trails: A Key to Management with Baits 5
If the ants are not visiting the bait, then change to
another brand. This is usually sufficient to initiate
feeding again. Of course none of these techniques
will succeed without thorough pre-baiting surveys,
and the sufficient number and proper placement of
bait stations.