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.

Mobility, longevity and activity of chlorfenapyr in soils treated at a termiticidal rate

“…17 Based on extrapolation from the brief-exposure studies, chlorfenapyr was not as toxic in the present study as expected. In the study of Rust and Saran, 17 4 h of exposure to 10% of the labeled rate causes the same mortality as observed in 7 days of forced exposure. It is possible that the maximum dose was taken up by the termite within 4 h, and additional exposure time did not result in higher mortality.…”

“…Exposure for 1 or 4 h to soil treated at various rates showed the delayed action observed in the present study, with mortality increasing from 1 to 5-7 days. 17 In the 3 day assays, there was a significant interaction between depth and time (F = 1.43; df = 50, 219; P = 0.0426) in describing toxicity of the soil. The depth by time interaction was significant in the 7 day bioassays as well (F = 1.95; df = 50, 219; P = 0.0006), and there were no other significant interactions.…”

“…it was less toxic) than chlorpyrifos, cypermethrin and fipronil. 17 In treated soil bioassays, brief exposures (1 and 4 h) led to mortality within 7 days to 50% of the labeled rate, and mortality increased with a longer exposure time. 17 Based on extrapolation from the brief-exposure studies, chlorfenapyr was not as toxic in the present study as expected.…”

“…17 In treated soil bioassays, brief exposures (1 and 4 h) led to mortality within 7 days to 50% of the labeled rate, and mortality increased with a longer exposure time. 17 Based on extrapolation from the brief-exposure studies, chlorfenapyr was not as toxic in the present study as expected. In the study of Rust and Saran, 17 4 h of exposure to 10% of the labeled rate causes the same mortality as observed in 7 days of forced exposure.…”

Evaluation of the pyrrole insecticide chlorfenapyr against pyrethroid resistant and susceptibleAnopheles funestus(Diptera: Culicidae)

“…Chlorfenapyr is used to control two‐spotted spider mites Tetranychus urticae (Herron & Rophail 2003) and subterranean termites Reticulitermes hesperus (Rust & Saran 2006). It has also been used in the cattle industry in impregnated ear tags to control Haematoba irritans (Guglielmone et al.…”