%D 2009 %0 MEDLINE %T Susceptibility of adult and larval stages of the horn fly , Haematobia irritans , to the entomopathogenic fungus Metarhizium anisopliae under field conditions . %J Vet Parasitol %V 166 %P 136-43 %A Mochi DA %A Monteiro AC %A Simi LD %A Sampaio AA %M pub19713044 %X The efficacy of M anisopliae strain E9 as a biological insecticide for the adult and larval stages of H irritans was assessed under field conditions . To assess larvicidal activity , nine heifers were randomly divided into three groups , which were maintained separated from each other . The first group ingested fungal spores encapsulated in alginate pellets . The second group ingested in natura spores that were grown on sterilized rice . In both groups , each animal received three meals a day , with each meal containing 2 x 10 ( 10 ) conidia . The third group received no treatment and was used as a control . Fecal samples from manure and whole dung pats were collected from each of the three separate pastures on the day that the animals were allocated and on days 1 , 3 , 6 , 9 and 12 afterwards . The fecal samples were tested for the presence of fungal colony forming units ( CFU ) , and the emergence of horn flies was observed in the dung pats . Significantly less ( P<0 . 01 ) adult horn flies were found in dung pats of the group treated with encapsulated fungi ( 11 . 7 ) than in those from the heifers treated with conidia in natura ( 27 . 9 ) or from the control group ( 29 . 5 ) . The fecal samples of the treated animals presented significantly higher numbers of M anisopliae CFUs then those from the untreated controls . We found that on day 9 fecal samples from animals given microencapsulated conidia had significantly higher CFUs than those from animals treated with conidia in natura . To assess adulticide activity , four heifers were sprayed with a suspension of 3 x 10 ( 10 ) conidial ( -1 ) of M anisopliae , and four control animals were sprayed with the same solution without conidial content . Four sprayings were done at five-day intervals , and all animals were photographed daily to observe the quantity of flies present . After the second spraying , we observed an average of 22 . 9 flies per animal ; untreated heifers had an average of 43 flies per animal ; thus , the treatment significantly ( P<0 . 05 ) decreases fly infestation . The results obtained from both tests show that M anisopliae strain E9 has a pathogenic effect on H irritans larvae in bovine manure when administered orally and on adult fly infestations when applied as a spray on the hosts .