Ants in Food Facilities
April 2024 Edition - Paul Gough ACE - Corporate IPM Manager
Ants are popular! A quick internet search for ant videos returns 112,000,000 results. They’re the subject of school science projects, university entomology labs, documentaries, movies, and TV shows. They even starred in an episode of McGyver (Season 1, Episode 6: Trumbo’s World).
While ants aren’t generally as dramatic in real life as they are on the screen, they are the number one household pest in the United States according to the National Pest Management Association. Because they’re so familiar, ants don’t tend to generate the same “ick” factor as cockroaches and other insects, and often don’t raise as much of an alarm. In a food facility, this tolerance can create a food safety risk. Ants have been shown to carry systemic pathogens and to be a source of cross-contamination for food-borne illnesses. An important part of managing ants in a food facility is to educate all employees that their presence is not normal or OK; ants are a food safety hazard that must be prevented, reported, and addressed with vigilance.
There are about 20 species of ants in the United States that are considered as “urban pests”, meaning they will readily invade and nest in, on, or around our buildings and structures. The most common of these seen in food facilities are pavement ants (associated with concrete floors), carpenter ants (which nest in soft, often water-damaged wood), and odorous house ants (which smell of rotten coconut when squashed and are opportunistic, nesting under and in just about anything).
Unlike stored product pest insects, which live in dry foods and grains, ants are social insects that live in hidden colonies. Worker ants travel to and from their food and moisture sources, gathering resources and bringing them back home. Mature colonies can have tens of thousands of workers. Ants that we see out in the open are likely the tip of the iceberg, and this is why reactive control efforts that only address what is seen often fail. Proactive measures and preemptive treatments will typically yield better and longer lasting results.
Ants are dedicated foragers that typically enter buildings from the exterior. Even when they’ve established an interior colony, they maintain seasonal outdoor access and typically obtain much of their food supply from the outside environment. Because of this, early spring efforts to eliminate harborage and access, and to utilize effective pest management products around the exterior perimeter, can have a devastating effect on ant colonies during their critical time of growth and reproduction.
A Spring cleanup should be performed as soon as the ground thaws on the exterior building perimeter and roof, before
the mowing season starts:
- Clean up litter, food debris, old (and new) weed growth; refresh the gravel perimeter as needed.
- Eliminate excessive landscaping plants, especially flowering and fruit-bearing shrubs and trees.
- Cut back any plants or trees that touch or overhang the building; remove vines.
- Limit or eliminate the use of wood mulch; it provides food and harborage for a variety of pests, and often comes pre-infested with ants.
- Ensure window seals are intact; seal or repair any cracks or damage to exterior walls, siding, and brickwork.
- Do not wait until grass is overgrown to begin seasonal landscaping efforts! At this point it is too late.
- A licensed pest control operator should apply a granular ant bait formulation to the perimeter.
- Ants often nest in or under plastic exterior rodent stations, which are warm and retain moisture; pest management professionals should be checking for this regularly and eliminating nests.
- The roof should be inspected for litter, food spillage, access points, and particularly evidence of leaks and water damage inside and out. Gutters should be checked for blockages and overflow, and enclosed overhanging eaves accessed and inspected.
In late summer when the weather has dried up, a 2nd application using liquid ant bait stations around the exterior perimeter can also be highly effective.
Interior inspection and maintenance should be conducted at the start of the season too. A Spring plant shutdown week might be an ideal time:
- Walls and floor/wall junctions in food areas should be checked for cracks, seams, and holes that need to be sealed; areas of deteriorated paint should be refreshed.
- Floors should be inspected for unsealed joints, cracks, and small holes left from removing equipment or wiring.
- Joints should be checked for buildup of compacted food product.
- Preventive application by a licensed pest control operator of liquid residual pest management products, applied in accordance with Food Handling Directions for Use, can be effective in areas such as storage that are not frequently covered in product or wet washed.
- In areas with a history of activity associated with hollow block or frame walls, a licensed pest control operator can apply dust or foam formulation pest management products into wall voids. This may require drilling and subsequently sealing or placing treatment ports in holes.
Inbound loads, particularly pallets, crates, wooden dunnage, and supplies/equipment brought in by contractors should be inspected for insect and rodent pests, including ants. Ants (and rodents) are frequently brought into facilities on items that have been stored outdoors.
When ants are identified in the facility, they should be reported immediately, and samples collected for identification by a pest management professional. Efforts should be made to identify the source and to find and eliminate the nest (often outdoors) if possible. If the nest(s) cannot be found or reached, an aggressive baiting program, with multiple placements and attractant bait types in accordance with label directions, should be implemented.
Large ant species, such as carpenter ants and field ants (which nest in lawns), can enter or be brought into facilities incidentally; without a colony to support them, they will quickly die off. Sticky traps placed along walls and edges and inside existing rodent traps can be a good way to capture stray ants that have entered through a doorway or on pallets.
Flying (winged) ants are the reproductive caste of a colony; their presence indicates a well-established and healthy population. Flying ants will exit the colony in large numbers triggered by temperature and humidity conditions, often indoors. Their only function is to mate and find new nesting sites; their primary impulse is to leave, so they will accumulate at windows and light sources. Insect light traps, vacuums, and addressing the source colony are the primary control methods. Space treatments will knock down those that have emerged, but emergence can go on for days or sometimes weeks. Proactively eliminating or stressing the colony so that reproductives don’t have the chance to develop is the best way to prevent flying ant outbreaks.
In summary, ants are a frequent and important pest of food facilities which pose a hazard to food safety that often goes unrecognized. Seasonal proactive management and preemptive treatment should be part of every food facility’s annual pest management plan.