Comparative efficacy of infective juveniles of Steinernema riobrave Cabanillas, Poinar, and Raulston (355 strain), S. carpocapsae (Weiser) (All strain), S. feltiae Filipjev (SN strain), Heterorhabditis bacteriophora Poinar (VS strain), H. indica Poinar, Karunakar, and David (HOM1 strain), and H. floridensis Nguyen, Gozel, Koppenhöfer, and Adams (K22 strain) were evaluated against engorged adult females of the multi-acaricide resistant Yucatan strain of Rhipicephalus microplus (Canestrini). Engorged female ticks were exposed to different concentrations of infective nematode juveniles (1,250, 2,500, and 5,000 per Petri dish) for 72 hours. Effects on mortality, egg mass weight, reproductive index, percentage inhibition of oviposition, and hatching percentage were assessed. A dose-dependent mortality response was recorded in ticks for all entomopathogenic nematodes except S. feltiae. Minimum LC50 (95% CL) values of 3,180.2 (2,957.9-3,419.3) and 490.9 (462.1-521.5) nematodes per dish were calculated for S. riobrave and H. floridensis, respectively. Each entomopathogenic nematode (except S. feltiae) significantly (p < 0.05) reduced the reproductive index of the engorged ticks, and the effect was dose-dependent because greater concentrations resulted in maximum reduction. No effect on egg hatchability was recorded in groups exposed to infective juveniles. Results demonstrated that some entomopathogenic nematodes also have acaropathogenic activity. S. riobrave and H. floridensis might be used as part of an integrated approach to control R. microplus resistant to various classes of acaricides.
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Vol. 44 • No. 1