In laboratory bioassays, boric acid (BA) mixed with soil caused significant subterranean termite mortality. In choice tests, eastern subterranean and Formosan subterranean termites were exposed to boric acid mixed with soil at concentrations of 0.05, 0.25, 0.50, 1.00, 2.00, and 4.00 percent Al (wt:wt). Termites could choose to remain in their main nests with non-treated substrate and adequate food, or to tunnel through BA-treated soil in an attached foraging tube to reach a satellite nest containing non-treated substrate and additional food. Termite survival, feeding, and tunneling, and gut protozoa populations were determined after 12 weeks. Exposure to BA-treated soil caused significant, steadily increasing mortality in both species, concomitant with a decrease in feeding as BA concentration increased. Boric acid was non-repellent, and termites removed BA-treated soil from foraging tubes and deposited it in main and satellite nests. Generally, at BA concentrations of 1.00-2.00% or less in soil, termite gut protozoa populations were not dose dependent and did not significantly decrease for either termite species as BA concentrations increased, except at the 4.00% concentration where termites appeared weakest. Overall, BA mixed in soil caused significant detrimental effects to both termite species.
