Potential of the insect growth regulator, fluazuron, in the control of Rhipicephalus sanguineus nymphs (Latreille, 1806) (Acari: Ixodidae): determination of the LD95 and LD50

Conventional pesticides have suffered two main drawbacks: (a) broad spectrum of action and (b) selection of target species resistant to the different active ingredients. Thus compounds that are less harmful to the environment and to human health, more specific and that do not induce resistance need to be developed. One alternative are insect growth regulators, such as fluazuron. The present study examined the efficacy of fluazuron (active ingredient of the acaricide Acatak®) and the sensitivity of Rhipicephalus sanguineus nymphs exposed to different doses of this chemical, and determined the lethal doses of fluazuron: 95% – LD₉₅ and 50% – LD₅₀. Different doses of fluazuron were applied in duplicates on the dorsal region of hosts (“pour on”). Distilled water was used in the control group. On the first day after the treatment with fluazuron, hosts were artificially infested with R. sanguineus nymphs. After engorgement, nymphs were removed, placed on Petri dishes, identified, and maintained in BOD incubator for 15 days. Dead R. sanguineus nymphs after the treatment with 13 different doses of fluazuron were quantified and the LD₉₅ was estimated to be 100 mg/kg and LD₅₀, 19.544 mg/kg (12.478–22.636), with a confidence interval of 95%. Nymphs of R. sanguineus were sensitive to fluazuron at various levels, indicating that this insect growth regulator (IGR) may be used to control this parasite in this stage of its biological cycle, reducing the significant damage it causes.