Effects of exposure duration on transfer of nonrepellent termiticides among workers of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae)

The potential for transfer of nonrepellent termiticide toxicants between workers of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was examined using two commercially available pesticide formulations and a simple donor-recipient model modified from current methods in the literature. Pesticides used were imidacloprid, formulated as Premise 75 WP, and fipronil, formulated as Termidor SC, in concentrations of 1, 10, and 100 ppm (weight of active ingredient/weight of sand) in sand. The results of the first experiment showed a significant increase in recipient mortality over control mortality when donor workers were treated with 100 ppm imidacloprid or 100 ppm fipronil. Although all three colonies studied were affected, one colony (colony 3) was affected to a significantly greater extent than the other colonies. This effect was not correlated with termite body size (dry mass). In a second study, recipient mortality was evaluated after exposure of donors to 1 ppm insecticide for 3, 6, 12, or 24 h, Recipient mortality indicated that these exposures did not consistently lead to lethal transfer of the insecticides.