ADULT BIOASSAY BASED AMITRAZ RESISTANCE STATUS IN RHIPICEPHALUS MICROPLUS POPULATIONS OF PUNJAB, INDIA

Amitraz resistance status was estimated in cattle tick, Rhipicephalus microplus populations collected from fifteen districts of the Punjab state using adult immersion test. A two-minute immersion protocol with various working concentrations (1-500 ppm) of formulated amitraz (Taktic 12.5% EC) in distilled water was adopted. The regression graphs of probit mortality of engorged female ticks against log concentrations of amitraz were utilized for estimation of slope of mortality, lethal concentration for 50% (LC50), 99% (LC99) and resistance factors (RF). The values of RF were found to be in the range of 0.20-4.55 indicating low level resistance status in eight field populations, whereas, seven were found susceptible to amitraz. Effects of amitraz on the various reproductive parameters of engorged R. microplus viz. egg mass weight, reproductive index, percentage inhibition of oviposition and hatchability percentage were assessed and found to be dose dependent and more discernible upon exposure with higher concentrations.