This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Don't assume an uptick in ant activity after setting out pesticide traps means the treatment failed. New UC Riverside research shows their behavior changes as chemicals make their way through a colony.
The research from the laboratory of UCR entomology professor Dong Hwan Choe was recently published in the journal Insects. It focused on how invasive Argentine ants, which are most commonly found in homes and gardens in Southern California, respond to two common insecticides used in ant baits: thiamethoxam and boric acid. While both treatments kill most worker ants in a colony, they do so at different rates.
Thiamethoxam killed all the workers within about seven days, while boric acid killed roughly 90% within about two weeks. The ants' behavior also varied widely in the days immediately following exposure. "During a previous study, we saw the ants behaving strangely on the first or second day after introducing a thiamethoxam bait, and it made us wonder if the behavior was related to the toxic effects of the insecticide," Choe said.
Thiamethoxam is a neonicotinoid known to be highly effective against various types of insects. Because it is also deadly to bees, there are more restrictions on its use; it cannot be sprayed on plants during flowering season. However, using it in stationary baits reduces the likelihood that it will harm insects that aren't the intended targets.
Choe and his students constructed transparent colonies in the laboratory to give them a clear view of the ants' activity both inside and outside their nesting sites. In healthy colonies, Argentine ants spread themselves throughout the available nesting space. Most remain inside caring for the queen, young ants and other colony members, while some workers venture outside to search for food.
After exposure to thiamethoxam, many more ants became much more active outside the nest, roaming through the foraging area before eventually dying. Because the chemical targets the nervous system, Choe suspects the extra activity may result from neurological effects. "It's like they're all high on nicotine," Choe said.
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