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 10(6), 10(7) and 10(8) 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 10(7) and 10(8) conidia ml(-1), and the JAB07 and AM09 B. bassiana isolates caused higher pupae mortality at a concentration of 10(8) conidia ml(-1). I. farinosa isolates were the most effective considering pupae mortality, with the CG195 inducing more deaths (56.6%) in the 10(8) 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 10(8) 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.

Efficiency of entomopathogenic fungi in the control of eggs and larvae of the horn fly Haematobia irritans (Diptera: Muscidae).

The present study assessed the pathogenic effect of isolates E9, IBCB425 and IBCB159 of the Metarhizium anisopliae fungus, JAB06, JAB07 and AM09 of Beauveria bassiana, IBCB133 and CB75 of Isaria fumosorosea (=Paecilomyces fumosoroseus) and CG189 and CG195 of Isaria farinosa (=Paecilomyces farinosus) against eggs and larvae of the horn fly Haematobia irritans. Eggs were inoculated with suspensions containing 10(6), 10(7) and 10(8)conidiaml(-1) of the fungal isolates and observed after 48h to determine viability. In the larvae study, eggs were allowed to hatch into fresh bovine feces that had been treated with 10(8), 10(7) or 10(6)conidiamgfeces(-1). In both studies, 5 days after initial procedures, all formed pupae were transferred to an incubator at 27+/-0.5 degrees C until the emergence of the adult flies was complete. The M. anisopliae isolates did not cause the death of H. irritans eggs, but they did promote the death of larvae that hatched from treated eggs, and therefore increased the total mortality. Isolate E9 promoted 100% mortality of treated larvae at a concentration of 10(8)conidiaml(-1). For the B. bassiana isolates, no activity was observed against insect eggs or larvae. Both I. fumosorosea isolates promoted significant mortality (p<0.05) of eggs at every concentration of conidia. Isolate CG195 of I. farinosa increased the mortality of larvae and pupae that hatched from treated eggs and promoted significant total mortality (p<0.05) of the insect at every concentration of conidia.