The Pests

Ants in a Kitchen: Why a Spray Can Make Some Colonies Worse

Written for: Kitchen managers, bar managers, maintenance staff

Parts of this page marked Professional synthesis, not law are a Board Certified Entomologist's reading of published records. They are not legal rules, they are not legal advice, and they are written to read the same for an owner, a customer, or either side's counsel.

Ant lines are a small share of restaurant pest citations, and most are critical when they appear (what inspectors cite). What makes ants worth a page is that the instinctive response, a can of spray along the trail, is the one that makes a particular ant worse.

Baits, not sprays

Baits are a key tool for managing ants and the only type of insecticide recommended in most situations. — UC IPM, Pest Notes: Ants

Spraying ants indoors with pesticides will not prevent more ants from entering. — UC IPM, Pest Notes: Ants

A bait works because the foragers carry it back to the colony. A spray kills the foragers you can see and leaves the colony, and the next day’s foragers, untouched. In a kitchen the spray is also a critical citation (who may apply pesticide).

The Pharaoh ant: a spray can split the colony

The Pharaoh ant is the small, pale yellow ant that turns up inside heated buildings year round. Its colonies have many queens, and they reproduce by splitting, a process called budding. A spray can trigger it.

New colonies begin by budding where groups of workers carry brood stages to new locations. — UC IPM, Ant Key: Pharaoh ant

Budding may also be triggered by insecticide sprays applied to trailing workers. — UC IPM, Ant Key: Pharaoh ant

Non-repellent baits (such as boric acid, hydramethylon or sulfonamide) should be used, as repellent baits can worsen the situation by causing the colony to fracture and bud. — University of Florida IFAS Extension, EENY-290, Pharaoh Ant

Do not use liquid or dust insecticides; they could spread ants, making the problem worse. — Utah State University Extension, Pharaoh Ant

Use a bait specific to the pharaoh ant. — Utah State University Extension, Pharaoh Ant

So a Pharaoh ant trail along the dish-area wall that gets sprayed on Monday can be three trails on three walls by Friday. The program is a non-repellent bait placed on the trails and left alone, and a technician who knows which ant it is before choosing the product.

The Argentine ant

The Argentine ant, the small brown ant that trails in long lines in summer, also has many queens and also spreads by budding; the published description is of budding as its normal way of founding colonies:

New colonies are established in the spring and summer and are propagated by budding, where one or more newly mated queens crawl out of an established colony with a group of workers. — UC IPM, Ant Key: Argentine ant

The recommended control is again bait, timed to the colony’s low point:

Use insecticidal baits, especially during winter – early spring when populations are smaller. — Utah State University Extension, Argentine Ant

I did not find a published source that says a spray triggers budding in the Argentine ant the way it does in the Pharaoh ant, so this page does not claim it. What the sources do say is enough: bait, not spray, for both.

Do not generalize

Professional synthesis, not law. The budding problem belongs to ants whose colonies have many queens and can split; the Pharaoh ant is the documented case. It is not a property of ants in general, and this site will not tell you that “spraying scatters ants.” It will tell you that in a kitchen the spray is a citation, that a bait is what the extension literature recommends for nearly every ant, and that identifying the species before treating is the step that decides which bait. That identification is what your pest company is for (questions to ask), and a photo to (801) 477-0223 will get you the name the same day.

Outside, the Exclusion Walk covers the trail’s point of entry: the gap at the threshold, the conduit penetration, the crack at the slab.