Efficacy of 1% fipronil dust of activated carbon against subterranean termite Coptotermes formosanus Shiraki in laboratory conditions

Abstract

Toxicity and horizontal transmission of 1% fipronil dust of activated carbon were measured using the subterranean termite Coptotermes formosanus Shiraki in laboratory conditions. 1% fipronil dust of activated carbon has delayed toxicity towards C. formosanus compared with 0.5% fipronil dust of French chalk; knockdown times KT₅₀ and KT₉₀ were delayed by >9 and >15 h respectively. Furthermore, 1% fipronil dust of activated carbon showed excellent primary and secondary horizontal transfer levels. In primary horizontal transfer, recipient mortalities reached 100% by 24, 48 and 72 h at donor-recipient ratios of 1:1, 1:5 and 1:10, respectively. High transfer efficacies were also found if donor-recipient ratios were greatly increased: mortality reached 100% at 9 d at ratio 1:25 and >90% at 12 d at 1:50. In secondary horizontal transfer, the toxicant transmitting ability of C. formosanus was greater when the primary horizontal transfer ratio was lower, and the highest transfer efficacy was found with a donor-recipient ratio of 1:1 - recipient mortalities reached 100% at 5 d and 11 d, respectively. Application of 1% fipronil dust of activated carbon overcomes the problem that that too high a concentration kills termites before they can contaminate their nestmates, while a lower concentration may not supply a sufficient dose for effective transfer from treated to untreated termites; this preparation has delayed toxicity, dose-dependent toxicity in horizontal transfer and high efficacy to control C. formosanus.