Efficacy of entomopathogenic nematodes at different spray pressures on Stomoxys calcitrans larvae (Diptera: Muscidae) in by-products of sugarcane mills

Abstract Stomoxys calcitrans is a hematophagous dipteran. The study aimed to evaluate the influence of spraying pressure on the efficacy of entomopathogenic nematodes (EPNs) on S. calcitrans larvae in sugarcane byproducts. Infectious juveniles (IJs) of Heterorhabditis bacteriophora, Heterorhabditis baujardi and Heterorhabditis indica were applied (200 IJs/larva) in water or 50% vinasse suspensions at pressures of 60, 70 and 80 psi to sugarcane straw, sugarcane bagasse and filter cake in plastic trays containing larvae. Control groups were not subjected to spraying. The efficacy of EPNs carried in water was not significantly reduced by spraying pressure when applied to bagasse and filter cake, but a lower larvae mortality was observed in straw for all EPNs applied at 80 psi and for H. baujardi and H. indica at 60 and 70 psi. Spraying of EPNs in vinasse did not significantly reduce the efficacy of all species in bagasse, but a reduction was observed in straw and filter cake depending on pressure. EPNs caused above 80% larvae mortality in most experiments. Spray-applied EPNs can infect and kill stable fly larvae in sugarcane substrates; however, their efficacy is influenced by spray pressure and carrier, as well as the treated substrate itself.