[Ant Control] Controlling Ants

Editor’s note: In both the first and second books of his Practical Guide for Pest Control Professionals series, William H Robinson provides information in a readable, educational format. Following are excerpts on ants from the two books, The Service Technician’s Field Manual, and The Service Technician’s Inspection and Identification Manual. To order, visit PCT’s Online Bookstore at www.pctonline.com/store.
 

Ants have a range of habits: some are solitary, some live in large colonies; some are plant feeders and some are parasites or predators. They have chewing mouthparts, and they use their mandibles to chew wood and build nests to contain their colonies. The colony survives through a system of dividing the labor of building and maintaining it among individuals. Queens originate the colony and lay eggs; workers, which are sterile females, gather food, maintain and repair, and defend the colony.

New ant colonies usually start with a mating flight: males and females fly from the nest and mate in the air or on the ground. After mating, the female forms a nest by making a brood chamber, and begins laying eggs. Workers of the first brood forage and feed the queen, expand the nest, and care for the next brood. The founding queen continues to lay eggs and remains in the nest. When the colony reaches a size of several thousand workers, the queen lays eggs that develop into reproductive females and males, and the process starts over.
 

Ant Management.

Ant infestations are often indicated by the presence of winged adults indoors. Infestations can be monitored by using feeding stations baited with a non-toxic food, then, at regular intervals, counting the number of ants visiting each station. Checking monitoring stations at the same time each day can provide information on abundance and colony activity.

The action threshold for ant control is determined by the tolerance level of the residents of a site. In IPM programs for schools, the action threshold for ants in classrooms and kitchens may be as low as one or two. Post-treatment monitoring is usually done by counting the number of complaints from building inhabitants, without regard to the ant species involved.

Most ant control programs start after a report of ants indoors. However, ants in buildings also may be non-infesting species that collect honeydew from insects on plants adjacent to the building.

What follows is a review of how various insecticides are transferred by ants:
 

Granular Insecticides.

The use of granular insecticides is primarily for outdoor pests, including ants. Granules can be applied to bare soil, turfgrass, and mulch as a spot, limited-area treatment, or entire perimeter treatment. The active ingredient is attached to an inert clay or organic material that acts as a temporary carrier. The carrier eventually degrades or is incorporated into the soil. The release of the insecticide may be enhanced by moisture in the soil or in the thatch layer in turfgrass.

Granules may be designed to be transported to the nests of ants, and the insecticide distributed to immature stages and nestmates. The size of the granules targeted for ants may correspond to the size of the mouthparts. Some formulations are designed to be small to enhance penetration of mulch or turfgrass thatch. Light-colored granules can enable better monitoring during application and ensure uniform coverage. Some carriers act as soil conditioners to promote aeration of treated soil and can degrade to provide micronutrients to plants.
 

Baits.

A variety of active ingredients, from borates to neonicotinoids, have been incorporated into ant baits. The consistency of baits includes liquid, solid (granular), semi-solid, paste and gel. Moist baits containing a high (50 to 75 percent) percentage of water are attractive to ants, which find their food by random searching, using their antennae and sensitive mouthparts to detect odors and moisture. They are naturally attracted to moist bait formulations.

Transfer of a lethal dose, referred to as horizontal transfer, can occur between ants. The actual transfer may be through mutual grooming, food sharing, eating feces, eating dead bodies or cast skins, or consuming regurgitated liquid. Formulations with low doses or slow-acting insecticides provide for the donor individuals to return to the nest site or harborage before the insecticide takes effect. Vertical transfer is between different generations of the same species, such as from adults to immatures.

Worker ants gather and redistribute liquid carbohydrates and proteins gathered during foraging. Food sharing generally occurs for all foods, but especially carbohydrates. This may be because of the high energy requirements of foraging workers, or the demands of the developing larvae. Liquid ant baits used in household pest control may have only carbohydrate ingredients or both carbohydrate and protein components.

Granular bait also is shared among workers. Workers of the same colony may not transfer solid food, but they can exchange liquid extracted from the bait. In some species, foragers give food items to an intermediate nestmate at the nest periphery, rarely bringing a food item into the nest.

Transfer of particulate active ingredient material may occur by direct physical contact between treated and untreated individuals. Typically this is from WP and SC formulation residues on nonporous surfaces and the initial pick up of a large dose. This type of secondary transfer is most effective against ants (and cockroaches) that are often in crowded harborages for long periods. This type of secondary transfer is dependent on individual pests acquiring a sufficient dose of insecticide powder or crystals to provide for dislodgeable residues.