Lethal and sub-lethal impacts of oil-formulated fungal biopesticides on house fly populations in simulated field settings (biocosms)

Control strategies for house flies in commercial poultry houses can include cultural, biological and chemical tactics; however, use of broad-spectrum chemicals is thought to be the only reliable tool to manage ‘fly burst’ situations. Our aim was to exploit post-eclosion resting behaviors of teneral flies to evaluate the population control potential of Beauveria bassiana and Metarhizium anisopliae in biocosms, which simulate field conditions. Experimental biocosms were created in plastic boxes where vertical walls were fitted with sprayed plastic sheeting (blank oil or conidia in oil). A cohort of 300 fly pupae was added to each biocosm; on emergence, the adult flies moved to the vertical surfaces to expand and harden their wings, a behavior observed in commercial facilities. The vertical, treated plastic sheets in the biocosm simulated field exposure. The biocosms were monitored daily for mortality and fecundity and egg viability until all flies had died. Fungal treated biocosms resulted in 100% mortality within 10-17 days, depending on the fungal species. Treated populations also showed significant reduction in egg viability and life-time fecundity. Furthermore, >20% reduction in basic reproductive rate was observed in treated populations. As part of an overall IPM program, the application of oil-formulated entomopathogenic fungi to plastic-clad, vertical surfaces near the poultry manure could suppress existing fly populations and substantially reduce population growth rates in poultry houses, reducing the probability of ‘fly burst’ situations. Further studies will focus on optimizing application parameters and validating these strategies under actual field conditions in poultry houses.