Toxicity, Repellency, and Transfer of Chlorfenapyr Against Western Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract

Chlorfenapyr is a slow-acting insecticide against western subterranean termite, Reticulitermes hesperus Banks, when applied to sand. The LD50 at day 7 for workers is 29.98 ng per termite and considerably higher than that of chlorpyrifos (14.01), cypermethrin (3.21), and fipronil (0.16). Brief exposures to sand treated with chlorfenapyr resulted in dose-dependent mortality over a broad range of concentrations. Brief 1-h exposures to > or =75 ppm provided >88% kill of termites at day 7. Chlorfenapyr deposits did not repel termites, even at 300 ppm. Termites tunneled from 0.1 to 1.8 cm into sand treated with 10- to 300-ppm chlorfenapyr deposits, resulting in > or =70% mortality. Within 1 h after being exposed to 50 ppm chlorfenapyr, approximately 17% of the termites exhibited impaired responses to synthetic trail pheromone. By 4 h, nearly 60% of the workers were not able to follow a 10 fg/cm pheromone trail. There was a direct linear relationship of the uptake of [14C]chlorfenapyr as concentration and duration of exposure increased. The percentage of chlorfenapyr transferred to recipients varied from 13.3 to 38.4%. Donors exposed for 1 h transferred a greater percentage of chlorfenapyr than did donors exposed for 4 h. A 1-h exposure on 100-ppm deposits provided sufficient uptake to kill 100% of the donors and sufficient transfer to kill 96% of the recipients. There was not enough transfer for recipients to serve as secondary donors and kill other termites. Horizontal transfer is limited to contact with the original donor and by the decreased mobility of workers within 4-8 h after exposure to treated sand. The effectiveness of chlorfenapyr barrier treatments is primarily due to its nonrepellency and delayed toxicity.

Experimental hut evaluation of the pyrrole insecticide chlorfenapyr on bed nets for the control of Anopheles arabiensis and Culex quinquefasciatus

“…Both hut trials, supported by tunnel tests, indicate that the lower chlorfenapyr dosages (100-250 mg ⁄ m 2 ) are no less effective than higher dosages against A. arabiensis and C. quinquefasciatus. Against termites, the effectiveness of chlorfenapyr as a barrier treatment is largely attributed to its non-repellent toxic activity and to its long half-life which is about one year in soil (Rust & Saran 2006). Against mosquitoes, N'Guessan et al (2007b) observed that chlorfenapyr is non-irritant at low dosages but stimulates take-offs at higher dosages.…”

Contact Versus Feeding Intoxication by Fipronil in <I>Reticulitermes</I> Termites (Isoptera: Rhinotermitidae): Laboratory Evaluation of Toxicity, Uptake, Clearance, and Transfer Among Individuals

“…Observational data from Þeld plots have provided evidence of termite mortality away from the treated soil (Potter andHillery 2002, Kard 2003). Several factors can affect the transfer process: inherent insecticide toxicity and its concentration, substrate type, exposure time of the donor, and time expired after exposure (Shelton and Grace 2003, Rust and Saran 2006, Tsunoda 2006, Saran and Rust 2007. Dissemination of insecticide may be caused by horizontal transmission through contact or social behaviors.…”

“…A study by Spomer et al (2008) revealed that transfer occurs in the Þrst 6 h of donorÐ recipient interaction and is positively affected by temperature. Transfer of Þpronil or chlorfenapyr from R. hesperus-treated termites to naṏve termites can occur by contact (Haagsma 2003, Rust and Saran 2006, Saran and Rust 2007. Tomalski and Vargo (2004) studied the colony-level effect of imidacloprid (another nonrepellent termiticide) on R. flavipes.…”

Concentration-Dependent Degradation of Three Termiticides in Soil Under Laboratory Conditions and Their Bioavailability to Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

“…These termiticides are considered to be more effective in controlling termites by killing them some distances away from the treated structures (Potter and Hillery 2002). However, recent studies have shown that the extent of horizontal transfer of termiticide among foragers was limited to 5Ð 6 m from the treated barrier (Osbrink et al 2005, Su 2005, Rust and Saran 2006, Saran and Rust 2007. Thus, the residual amounts and bioavailability of termiticides over time may be the primary factors contributing to the termiticide efÞ-cacy in soil.…”