School IPM

IPM for Ants in Schools

Introduction

Ants become pests when they invade buildings in search of food or shelter. It is often very difficult and laborious to eliminate most ants from their outside habitat, therefore management should be targeted at preventing ants from invading structures. Unfortunately, prevention is not always successful and control actions must be implemented.

Although ants are often regarded as pestiferous, it should be noted that ants are beneficial in several ways. First, ants are predators of numerous pest insects, including fly larvae and termites. Secondly, ants aerate soil and recycle dead animal and vegetable material thus aiding in the formation of top soil. Additionally, ants are responsible for pollinating plants in some areas. Ants provide a great service to the environment, and management efforts that prevent or control ants are preferred over practices that aim to eliminate ants.

Note that it is not within the scope of this project to address either carpenter ants or fire ants.

Identification and Biology

Ants are social insects that live in colonies whose members are divided into three castes: workers, queens, males. The responsibilities of the worker caste are to enlarge and repair the nest, forage for food, care for the young and queen, and defend the colony. The queen's primary duties are egg laying and directing the activities of the colony while males serve only to mate with the queens.

Ants pass through four stages of development: egg, larva, pupa, and adult. After mating with males, queens lay eggs that hatch into blind, legless larvae. The larvae are fed and cared for by worker ants. At the end of the larval stage they turn into pupae which do not feed. After a short period of time, adult ants emerge from their pupal stage and become worker ants.

The first step in management of pest ants is proper identification. Since there are many types of ants that may invade a structure it is important to identify the type of ant because most ants differ in their habits and food preferences. See Identifying Ants and Common House-Invading Ant Species.

The University of Florida offers a poster that combines line drawings, color and scanning electron microscope photographs in an identification key to help individuals identify the most common structure-invading ants.

Damage

Some species of ants such as thief, Pharaoh, and Argentine ants, are particularly prone to infesting food. Inside buildings, these ants are primarily a nuisance since they almost never sting or bite. Since ants walk over many different kinds of surfaces and sometimes feed on dead animals and insects, it is possible that they can carry disease-causing organisms to human food. It should always be assumed that ant-infested food stuffs have been exposed to organisms that can cause spoilage, and the food should be thrown away.

Detection and Monitoring

Visual inspection is the most useful monitoring technique for detecting ants and can be very useful in preventing a developing infestation. A thorough inspection and prevention program is required to locate the ant source.

• Constructing a map of the school on which you can note problem areas and areas needing repair.
• A bright flashlight is mandatory. Kneepads and a mirror are helpful.
• A sealant such as outdoor caulk can be used to seal holes and cracks that ants could use to gain entry to the structure.
• Keep accurate records during the monitoring program to help formulate an IPM plan and evaluate its effectiveness.
• Careful attention should be paid to indoor areas such as kitchens and food preparation areas.
• An ant infestation may indicate that there has been a change in the methods of storing food or food waste that allows increased food sources for ants. Note how food and food wastes are stored in the area, and whether refuse containers are emptied and cleaned regularly. Inspect recycling bins to ensure that recyclables have been cleaned before storage.
• Interact with kitchen staff and custodians to learn more about the problem from their perspective.
• Ants can be attracted to snacks kept in classrooms or teachers break rooms as well as to sweet drinks accidentally spilled on the floor.

Management Options

Habitat Modification

The environment should be modified to reduce ant entryways and access to food. With quality materials and careful work, the alteration will be permanent and make a long-term impact on the number of ant invasions.

Caulking

• Caulk all potential entryways with a silicone caulking compound.
• Use mildew-resistant caulk in moist areas.
• It is not necessary or practical to seal all cracks, but begin with the access point that the current trail of ants is using.
• Always carry caulk when making inspections and seal as many cracks as time allows, especially those around baseboards, cupboards, pipes, sinks, toilets, and electrical outlets. Silicone caulks are flexible, easy to apply, and long-lasting.
• Weather-strip around doors and windows where ants may enter.

Sanitation

Sanitation eliminates food for ants. Thorough daily cleaning of school kitchens and food preparation areas is essential.

• Sweep and mop floors.
• Drain all sinks and remove any food debris.
• If children regularly receive snacks in classrooms, these floors should be vacuumed and/or mopped daily.
• Periodically give all food preparation areas an complete cleaning, focusing on areas where grease and food debris accumulate. These include drains, vents, deep fat fryers, ovens, stoves, and hard-to-reach areas behind or between appliances. Thoroughly clean the area with a powerful vacuum.
• At the end of each day, remove all garbage containing food from the building.
• Use soapy water to wash any bottles, cans, wrappings, and other items that have food residues clinging to them before storing them for recycling.
• If dishes cannot be washed right away, it is very important that they at least be rinsed to remove all food debris.
• Place garbage in sealed plastic bags before it is placed into a rodent-proof dumpster or other storage receptacle.
• Keep garbage cans and dumpsters as clean as possible to deny food to ants, roaches, flies, mice, and rats.

Proper Food Storage

• Food not kept in the refrigerator should be kept in containers that close tightly. Cardboard boxes can be penetrated by ants.
• Keep particularly attractive substances, like sugar and honey, in a refrigerator.
• Although refrigerator storage is usually safe, ants sometimes get into refrigerators and freezers even when the seals appear intact. When this occurs, a light, temporary coating of petroleum jelly on the edge of the refrigerator seal will exclude the ants.
• Screw-top jars are ant-proof only if the lid has a rubber seal since the ants can follow the spiral ridges to get into the jar.
• Glass containers with rubber gaskets or plastic containers with tight-fitting, snap-top lids are also ant-proof.
• Upon arrival to the building, transfer packaged food into plastic or glass containers. To prevent roach problems, do not bring shipping boxes into the food preparation area. Instead, boxes should be broken down and stored away from the kitchen in a cool area until removed for recycling.
• Advise students and teachers not to leave unsealed food items in their desks or lockers.
• Any food kept in offices or classrooms should be stored in ant-proof containers.

Physical Controls

At times when only a few ants are noticed foraging in an area, squashing or crushing the ants may be effective.

Vacuuming

• Use a strong vacuum to vacuum up trails of ants effortlessly and quickly.
• Vacuum a tablespoon of corn starch to kill ants in the vacuum bag.

Detergent Barrier

Temporary "moats" of detergent and water may be useful during heavy ant invasions.

• Containers of food or food waste which must remain open during working hours can be placed in large, shallow pans filled with water mixed with a small amount of detergent.
• Use this technique to protect potted plants from ants that may be attracted to nectar produced by the plant or to honeydew produced by plant-feeding insects. Elevate the pot above the detergent-and-water mixture by placing it on an overturned saucer. Make sure the limbs and leaves of the plant are not in contact with surfaces that ants could use as bridges.

Chemical Controls

At times, non-chemical methods alone prove insufficient to solve the problem. Integrating a pesticide into your management program may be necessary to gain control of the ant problem.

Pesticides must be used in accordance with their EPA-approved label directions. Applicators must be certified to apply pesticides and should always wear protective equipment during applications. All labels and Material Safety Data Sheets (MSDS) for the pesticide products authorized for use in the IPM program should be maintained on file. Do not apply these materials when buildings are occupied, and never apply them where they might wash into drains or sewers.

When treating ants, all baits and dusts should be placed in cracks, crevices, and in precise areas where ants are active. See Tips For Controlling Specific Ants.

Detergent and Water

When ants invade a classroom or food preparation area, use a mixture of soap and water in a spray bottle. This mixture will quickly kill the ants which can then be wiped up with a sponge and washed down the drain. Each classroom, cafeteria, and food preparation area should be equipped with such a spray bottle so teachers and staff can safely deal with emergencies.

Boric Acid

Boric acid is one of the most valuable chemical control tools in an integrated ant management program. It is formulated as a dust, gel bait, and aerosol. It acts as a stomach poison and is relatively non-toxic to mammals. If kept dry, boric acid dust remains effective for long periods of time.

• When applying boric acid dust, wear a dust mask to avoid breathing the material.
• Use a bulb duster to apply a light dusting in cracks and crevices. This is recommended over dusting large, open areas.
• Boric acid is approved for crack and crevice treatment in kitchen and food preparation areas.
• Boric acid can be dusted into wall voids and spaces behind and under cabinets.

Diatomaceous Earth and Silica Aerogel

These are insecticidal dusts that can be used for ant control. Diatomaceous earth is made from fossilized diatoms, and silica gel is produced from sand. Both kill insects by desiccation; they absorb the waxy layer from the insect's outer covering, which causes dehydration and death. Although these materials are not poisonous to humans directly, the fine dust travels freely through the air and can be irritating to the eyes and lungs; therefore, use a dust mask and goggles during application.

Diatomaceous earth and silica aerogel are especially useful in wall voids and similar closed spaces. During construction and remodeling these dusts can be blown into such spaces, and in finished buildings they can be applied by drilling tiny holes in the walls. These dusts are also useful in crack and crevice treatments.

Some products combine diatomaceous earth or silica gel with pyrethrins. The pyrethrins provide a quick knock-down of the ants, and the dusts provide long-term control.

Ant Baits

Baits greatly reduce the amount of pesticide that must be used to kill ants. Foraging ants take the bait back to the nest to feed to other members of the colony resulting in colony death. Even if the queen is not killed, baits will usually stop an ant invasion. If a colony has been starved by effective sanitation measures, baits will be more readily accepted.

Always place baits out of sight and reach of children, or, if this is not possible, use baits at night or on weekends and remove when children are in school.

Some ants are very susceptible to baits, some are less so. There are many reasons for these differences, only some of which we understand. If you are having difficulty in controlling ants with a bait, the following points may be helpful:

• It is important to correctly identify the species of ant that is invading the school since each species differs in its food preferences. Some baits contain a sweet attractant and others use a protein or oily attractant. Therefore, the attractant in the bait must be preferred by the type of ant identified. If you cannot determine the type of attractant by looking at the label, call the manufacturer for more information. You should also ask if the company has data to support the efficacy of their product against the ant species you are dealing with.
• After setting out bait, observe to see if the target ant is taking the bait.
• Ant colonies have changing nutritional requirements that can pose problems in baiting. A colony that accepted a protein bait one week may be more interested in a sugar bait the next.
• The nesting and foraging environment can also affect bait acceptance. Ants nesting and foraging in dry areas will be more interested in baits with a high water content than will ants nesting in moist environments.
• When there are several competing ant species in one area, ants non-target ants may accept your bait more readily than the pest ant and, in some cases, prevent the pest ant from getting to the bait.
• Do not spray pesticides when using baits. Bait stations contaminated with pesticide are repellent to ants, and sprays disperse the ant infestation, making it more difficult to place baits effectively.
• Place bait stations along foraging trails, but do not disturb ant trails between the nest and the bait. Killing the ants or disturbing the trails prevents the ants from taking the bait back to the colony to kill nest mates.
• Do not apply bait until an ant problem is noticed. If you use baits preventively you may attract ants into the building.
• Some baits come packaged in plastic disc "bait stations" that come with double-sided tape so they can be attached to various surfaces out of view. It is important to remove bait stations once control is attained because the stations may serve as harborage for cockroaches. Some baits are formulated as granules or gels that can be injected into wall voids through small holes. Gel baits can also be placed near ant trails in inconspicuous places where they will not be disturbed.

Edited by: Jerry Gahlhoff, University of Florida.
Originally written by: S. Darr, T. Drlik, H. Olkowski, and W. Olkowski

Photographs: University of Florida

Published: April, 1998