Entomopathogenic fungal activity against pupae and adult Haematobia irritans (Diptera: Muscidae)

The horn fly Haematobia irritans is one of the most important ectoparasites associated with grazing bovines. This study investigated the pathogenic activity of Metarhizium anisopliae (E9, IBCB425 and IBCB159), Beauveria bassiana (JAB06, JAB07 and AM09), Isaria fumosorosea (=Paecilomyces fumosoroseus) (IBCB133 and CB75) and Isaria farinosa (=Paecilomyces farinosus) (CG189 and CG195) fungi isolates on pupae and adult H. irritans. Groups of 20 pupae and 30 adult flies were respectively bathed and sprayed with fungal isolate suspensions containing 106, 107 and 108 conidia ml−1 in bioassays conducted in laboratories. In both assays the adult flies were fed bovine blood for 15 days, and death rates were assessed daily. The E9 and IBCB425 M. anisopliae isolates caused pupae death at concentrations of 107 and 108 conidia ml−1, and the JAB07 and AM09 B. bassiana isolates caused higher pupae mortality at a concentration of 108 conidia ml−1. I. farinosa isolates were the most effective considering pupae mortality, with the CG195 inducing more deaths (56.6%) in the 108 conidia ml−1 concentration suspension. Adult flies were more susceptible to the fungi's pathogenic action, since the E9 isolate of M. anisopliae and all of the B. bassiana induced death in 100% of the flies at the 108 conidia ml−1 concentration suspension. The I. fumosorosea and I. farinosa isolates, on the other hand, were less effective in controlling adult flies. In both stages, but mostly the adult phase, pathogenicity was great at higher conidial concentrations.