Ant foragers are ‘essential workers’

• If you only kill the ants you can see, the colony will make more.

• Target the colony, even if you have to use the foragers to do it.

Foraging pyramid ants (Dorymyrmex insanus) take down a caterpillar to bring home as dinner for their colony. PHOTO: COURTESY OF, AND COPYRIGHTED BY, GENE WHITE, PMIMAGES@EARTHLINK.NET

Ants are among the most common household pests that bring us into homes and businesses every day. You may be familiar with the heartburn-level frustration of returning a day or two later, watching active ants working a new area without any regard to the ants you dispatched earlier.

Here’s why: Like many people these days, the majority of ants are working safely from home. Only the ant foragers are “essential workers,” leaving the nest to get work done. Although it varies — some species don’t even have a home — the foragers of most pest ant species only make up between 5 percent and 10 percent of the colony. Most ant workers are tending the brood (eggs, larvae and pupae), tending the queen, or maintaining the nest. The really dangerous work of going out into the wide world to bring home the food is left to a small minority of mostly older workers.

In other words, if that’s where all your control measures are aimed, the colony will survive and generate a whole new brigade of foragers.

A BETTER WAY

There are several ways to target the colony, but only one of them can be done without the foragers. If you know where the colony is, don’t sprinkle bait around their doormat and wait. Rather, lift up their roof and make a direct application. Of course, this can only happen when you know where the colony is.

When your only access to the colony is through foragers, though, you have two main options:

• Non-repellent contact residuals can be picked up by foragers and translocated back to the colony to be spread by grooming. But while this can be extremely effective, it’s not always possible. Label restrictions can limit the use of these products, and many integrated pest management (IPM) program protocols don’t allow the use of contact residuals until other methods have been tried.
• Baits work by serving as the food that foraging ants take back to the colony. In the case of liquids and gels, the baits are taken in by the ants and shared through trophallaxis (food sharing) with other workers in the colony, but adult ants can’t eat solid food. The larvae serve as the colony’s stomach, and provide digestion of solid food. There is evidence that toxicants can pass from bait granules into some ants, but for baits to be effective, they have to deliver their actives to the colony. If the foragers are killed too quickly, there isn’t time for the toxicant to be spread far enough to eliminate the colony.

Getting control isn’t difficult if you can find the colony. But if all you can find are foragers, you will need to find a way to reach all the ants that are working from home.

You can reach Mark Sheperdigian, BCE, vice president of technical services, Rose Pest Solutions, Troy, Mich., at shep@rosepest.com.