Comparison of three Larval Immersion Tests in Syringe to evaluate acaricidal activity of chemical solutions

Abstract

The aim of this study was to compare Larval Immersion Test in syringes, originally proposed by Souza et al. (2008), with two modified bioassays proposed by Silva et al. (2011) and Sindhu et al. (2012). Rhipicephalus (Boophilus) microplus larvae were exposed to nine dilutions of commercial acaricide. After 24 hours, the number of dead larvae was counted. The LC50 for the three methods were 0.186%, 0.125% and 0.153%, respectively. Mortality of larvae exposed to chemical dilutions on Silva et al. (2011) were significantly higher than other methods at lower concentrations, probably in consequence of longer exposure time of larvae to solutions. However, modifications proposed by Sindhu et al. (2012) make technic execution more practical and safer.