Toxicity, repellency, and horizontal transfer of foam insecticides for remedial control of an invasive drywood termite, Cryptotermes brevis (Blattodea: Kalotermitidae)

Abstract

Laboratory tests were conducted to compare imidacloprid and fipronil foams against various criteria to determine the effect of the deposit conditions, exposure method, and exposure time on the toxicity, repellency, and horizontal transfer of selected foam insecticides. Results of toxicity assays showed that imidacloprid and fipronil foams caused significantly higher mortality than control treatments; however, fipronil foam in fresh or old deposits killed Cryptotermes brevis pseudergates more quickly in the short and continuous exposure tests than foam containing imidacloprid. In brief exposure tests, imidacloprid failed to kill all termites when exposed to fresh deposits and delayed total mortality when exposed to dry residues. The mortality of C. brevis pseudergates was also significantly quicker when the fipronil foam was applied topically compared with the imidacloprid foam. In the repellency test, termites were not repelled from the surface treated with fipronil foam, but more than 90% repellency was observed after 24 h of exposure to imidacloprid-treated surfaces. Moreover, the non-repellent mortality of C. brevis with fipronil was significantly higher than imidacloprid in avoidance tests. Results showed that fipronil was effectively transferred to untreated termites from live or dead donors exposed via residual and topical spray.