Evaluation of boric acid as a slow-acting toxicant against subterranean termites (Heterotermes and Odontotermes)

Various concentrations (100, 500, 1000, 5000 and 10000 ppm) of boric acid were tested in laboratory to check its potential as a slow-acting toxicant against subterranean termite, Heterotermes indicola (Rhinotermitidae: Isoptera). Under the tested concentrations, ELT 50 (Effective Lethal Dose to kill 50% of the exposed termites) values ranged from 2.7 to 5.4 days while ELT 90 were 4.5 and 9.1 days for the lowest and highest concentrations used in the lab trial. Choice feeding test showed that bait matrix treated with all the above concentrations was acceptable to termites. At a concentration of 10000 ppm, boric acid resulted in 91% mortality within two weeks when both the treated and untreated substrates were offered to H. indicola. Field testing of boric acid bait showed that it was readily fed upon by Odontotermes sp. while H. indicola avoided the bait after initial feeding exposure. However, it led to significant population suppression for both the genera of subterranean termites.