[Ant Control Issue] Ants in Your Plants

Features - Cover Feature: Ant Control Issue

The type of ant most likely to infest a food or beverage plant is primarily dependent on the region in which the plant is located and the type of food processed.

April 30, 2013
Lisa Lupo

With 200 species of ants in the U.S. with different habits, behaviors and food preferences, it is critical that the species be identified prior to attempting to eliminate it. The type of ant most likely to infest a food or beverage plant is primarily dependent on the region in which the plant is located and the type of food processed. But the most common can be grouped into three categories: tramp ants, Pharaoh ants and carpenter ants.

Pretend for a moment that you’re the QA manager of a food plant. It’s 4:45 on a Friday afternoon. Production is just about shut down for the weekend when an employee comes up to you to report that he saw an ant in the plant. It’s been a long week, and you’re definitely ready for the weekend. Do you:

A. Record it in the pest sighting logbook, figuring the technician will see it next time he comes in.

B. Jot yourself a quick note to take care of it first thing Monday morning.

C. Call your pest management technician for an emergency visit.

According to Joe Barile, technical service lead, PPM/Vector, for Bayer, the only correct answer is C. “If a QA manager suspects, sees, or has ant activity reported, they must act on it immediately,” Barile said. “If it is 4:45, and they’re shutting down for the weekend, they still need to act on it, or two ants can become thousands in minutes.”

While ants can carry and transfer disease bacteria, this is not as much an issue as with other pests, such as cockroaches and flies that feed and breed in pathogenic areas. But, because one ant that finds food in a plant can leave a trail for the entire colony of workers to follow, they can create adulteration hazards for the product in and around processing and storage areas.

“If you have a big ant problem, it’s probably indicative of other problems,” said Rockwell Labs’ Cisse Spragins. The most common reason for ant problems is lack of sanitation. “If ants are coming in, it will probably be because there is something there they want to eat,” she said.

Ants can be very finicky creatures, attracted to sweets one day and protein on another. “In food plants, ants will feed on certain things depending on what the colony needs,” Barile said. “Its individual needs are not as important as the colony’s as a whole.” For example, one day the ants may seek proteins needed for the queen to lay her eggs; on another, they may seek fats to store for energy. Thus, ant behavior can change based on the food the colony needs.

Food build up or spillage may be responsible for attracting the ants, or, said Hope Bowman, Western Pest Services entomologist and technical specialist, “Ants may be attracted to storage areas where food hasn’t been moved for a period of time. If there’s spillage, they are even more likely to find it.”

PMPs servicing food plants should pay particular attention to break rooms, where food spillage may occur, and employee locker rooms, where open foods may be stored, Bowman said. She recommends that plants have monthly or quarterly cleanout of lockers and locker rooms. By throwing out old food and keeping areas clean, a plant can guard against cockroaches and rodents as well as ants.

Tramp Ants invade facilities just to get resources and carry them back out. They don’t live or breed in the plant, but can cause contamination or adulteration hazards. The most common tramp ants include odorous house, Argentine, pavement and crazy ants:

Odorous House Ants

  • Colonies are very large and have multiple queens.
  • Can appear suddenly by the thousands.
  • Are opportunistic feeders, appearing suddenly, then disappearing.

Argentine Ants

  • Have super colonies that can spread for many square miles.
  • Are opportunistic feeders of food and water.
  • Are likely to appear in periods of drought.

Pharaoh Ants
are one of the smallest of the structural ant species. With multiple queens, care must be taken not to stress the colony, as it will “bud” into additional colonies, causing increased hazard. They:

  • Are extremely aggressive foragers.
  • Can enter through smallest of cracks and crevices.
  • Need a regular water source from moist food or free water.

Carpenter Ants
can be a huge problem in plants, even with the limited amount of wood. They:

  • Don’t actually eat wood, but seek out the moisture of damp wood of pallets or structures.
  • Will actively forage in the plant and feed on food debris.
  • Will forage 300 feet or more from the nest, primarily doing so at night.

Pavement Ants and Crazy Ants

  • Similar in behavior, these ants are foragers.
  • They lay trails to and from foods to provide other worker ants with a path.
  • Floor level sanitation is very important to destroy trails.


In addition to plant sanitation, Spragins said, “The most important thing is to not have ants get inside in the first place. You want to stop them outside before they get in and cause a problem.”

Ants can enter buildings through gaps, cracks and seams, as well as open dock doors and windows. Thus, the first step in keeping ants out is following standard pest-proofing practices: sealing all gaps, cracks and seams; keeping doors and windows closed; and ensuring these are well-sealed with fitted gaskets, door sweeps, etc. “The most obvious thing to do is to build them out,” Barile said.

Gaps also can occur around utility chases, with only 1/64-inch hole needed for an ant to get in and out. “Be sure these are sealed tight, tight, tight, because ants are very small,” he said.

University of Georgia Researcher Dan Suiter said it is important to be proactive with ant exclusion. When temperatures drop in the fall and winter, populations looking for places to overwinter can move indoors, causing a “major headache,” he said. “Do what you can to head off these extreme September and October populations.”

Chemical Control.
Exterior controls also can include chemical application, but one thing the experts all cautioned against is a plant manager attempting to self-treat. Restricted-use products should be used only by trained, certified applicators, but even using over-the-counter products can make the problem worse. “If you only spray,” Spragins said, “you are just chasing workers away; you’re not doing anything to eliminate the colony.”

This can be particularly at issue with ant species that have multiple queens. For example, Bowman said, Pharaoh ants will split rapidly and create new colonies, causing even greater problems for the food plant.

The most critical aspect of chemical use is ensuring it is labeled for that use, particularly for in-plant application. “Any chemical has to be approved,” Barile said. As such, he added, “label comprehension is critical.” If a product is used that is not labeled for food production areas, the FDA can designate the food as contaminated and not fit for consumption.

Spragins recommends PMPs treat around the outside perimeter with a weather-resistant granular bait. The worker ants will take the bait back to the nest to feed the queen and colony, thus eliminating the entire colony, rather than just the foraging workers.

The bait also can be placed on a slow-acting, non-repellent residual. The ant will get the chemical on its body then carry the bait and chemical back to its nest. “It is very effective when you have an active ant problem,” Spragins said. “The combination works better than either one by itself.”

PMPs should also focus on inspecting for ants, both outside and within the plant, Bowman said. They should look for areas and foods that could be attractive to the ants, as well as structural openings or defects through which the ants can enter. While inspecting rodent stations, PMPs also should look for ants, she said, as the stations can be treated, or baited, for the ants along with rodents.

“The best process is for the QA or safety manager to rely on a professional to provide the monitoring, diagnostics, inspection service, and communication on a regular basis,” Barile said. This communication should focus on:

  1. The PMP gaining a complete understanding of plant processes and people, including a sit-down meeting with all those who will be involved, then walking through the plant with the person who will be responsible for acting on recommendations.
  2. Two-way conversation including history of the plant and concerns of the processor, and the PMP’s initial observations of conducive conditions.
  3. Follow-up on all recommendations. “Food plants are often surprised when they hear the PMP talk about things they never knew contributed to pests,” Barile said, such as employee behavior, lighting, food in desk drawers and outside ornamentals.

“Pay attention to the service report,” Bowman added. “A technician may make a recommendation that is not necessarily pest specific, such as spillage or a leak. Know that there is a reason the technician is telling you about it.”


This article originally appeared in PCT’s sister publication, Quality Assurance & Food Safety. Lisa Lupo is the editor of QA magazine.

Ant drawings courtesy of Bayer Ant Identification Guide, available at http://bit.ly/ZmKEUl.