Discovery of the Rdl mutation in association with a cyclodiene resistant population of horn flies, Haematobia irritans (Diptera: Muscidae).

The horn fly, Haematobia irritans irritans, is an obligate blood-feeding parasite of cattle that causes significant economic impact in many countries. We investigated the resistance of a horn fly population from Louisiana/USA to endosulfan, a cyclodiene insecticide. Bioassays were performed in 2010 and 2011 in order to determine the resistance ratio of the population to endosulfan and a PCR assay was developed to detect the Rdl mutation which is the replacement of an alanine with a serine at the GABA receptor locus that has been associated with resistance to cyclodienes in other insect species.