EFFECT OF IVERMECTIN ON 3 FIELD POPULATIONS AND A LABORATORY STRAIN OF HAEMATOBIA-IRRITANS-EXIGUA (DIPTERA, MUSCIDAE)

Ivermectin (MK-933) was administered in the blood diet of Haematobia irritans exigua De Meijere in an in vitro bioassay to determine the concentration-response of three field populations and one laboratory strain. The bioassay was based on mortality at 48 h. Ivermectin was highly effective against H. i. exigua and susceptibility to ivermectin among the populations was similar. Male flies were more susceptible to ivermectin, with LC50s ranging from 32-53 ng/ml compared with a range of 42-61 ng/ml for females. Fecundity was reduced by 90% when flies were fed for 8 d on a sublethal concentration of 3 ng/ml.