Susceptibility of immature Ixodes scapularis (Acari: Ixodidae) to desiccants and an insecticidal soap.

Abstract

Efficacy of commercially available formulations of desiccants (Drione, Dri-die, diatomaceous earth) and insecticidal soap (Safer's) comprised of active ingredients were evaluated against Ixodes scapularis Say immatures in petri dish and grass turf bioassays. In petri dish bioassays at label rate, all products, except diatomaceous earth, provided a high degree of control by 24 and 48 h (71-100% mortality). Mortality of larvae exceeded 94% by 4 h after treatment with Drione (10 x label rate held at 85% RH), Dri-die (label rate held at both 85% and 98% RH) and Safer's insecticidal soap (10 x label rate held at 98% RH). Nymphal mortality was highest by 4 h after treatment with Safer's insecticidal soap (up to 96%). Larvae were more susceptible than nymphs to desiccants, however, nymphs were more susceptible than larvae to Safer's insecticidal soap. Immature ticks treated with Safer's insecticidal soap exhibited sublethal effects with significantly decreased attachment to hosts and no engorgement. In grass turf bioassays, mortality of nymphs was equivalent (85-95%) between treatments of chlorpyrifos (0.6 kg [AI]/ha, Safer's insecticidal soap, and Drione. In the same bioassays, nymphal mortality was moderate after treatment with Dri-die (23-29%) and low following application with diatomaceous earth (16%) and for untreated controls (6%).