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

Toxicity and 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 Talcum powder; knockdown times KT 50 and KT 90 were delayed by > 9 and > 15 h respectively. Furthermore, 1% fipronil dust of activated carbon showed excellent primary and secondary transfer levels. In primary 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 transfer, the toxicant transmitting ability of C. formosanus was greater when the primary 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 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. The results showed that 1% fipronil dust of activated carbon was non-repellent and readily transferred from treated to untreated termites. As the post-exposure time and doses increased, the mortalities of both donors and recipients increased. And it has delayed toxicity to control C. formosanus.