Pesticides make Argentine ants go crazy, sending them roaming or clustering before workers die

A recent study from the University of California, Riverside has revealed how exposure to two common insecticides affects Argentine ants. The research focused on thiamethoxam and boric acid, both of which are used in ant baits, and how they change the behavior of the invading species.

Thiamethoxam, known to be highly effective against various insects but also harmful to bees, killed the majority of workers within about seven days. However, the study found that many ants became unusually active outside the nest before eventually dying. The researchers believe this heightened activity may be due to neurological effects, as the insecticide mimics nicotine's effects, overstimulating the nervous system and causing paralysis.

In contrast, boric acid had the opposite effect. It caused affected ants to stop foraging and gather tightly inside the nesting space, especially near water sources. This behavior could be due to boric acid's impact on the ants' digestive and excretory systems. The ants' clustering near water may be a result of these internal damages.

Understanding these behavioral changes could help pest control professionals and consumers better interpret what they observe after setting out ant bait. For instance, ants stopping foraging after encountering boric acid might appear to have been quickly eliminated, but surviving ants could later reappear.

The findings could also influence how ant baits are formulated. Lower doses of thiamethoxam might prolong the unusual roaming behavior, which could be beneficial for pest control. However, it's important to note that both chemicals are effective at killing most of the ants in a colony, but they may not always kill the queen. Therefore, a single application of bait often leads to temporary relief from the pests, as another invasion can occur when the queen hatches a new brood.