Researchers tested special fungi (Metarhizium spp.) as a natural way to control house flies, which spread diseases and are becoming resistant to common pesticides. They found that two fungal strains were very effective at killing fly larvae and pupae, and these fungi could still grow well when combined with certain insecticides. This means farmers and pest control professionals could use these fungi together with specific pesticides as part of a more sustainable approach to controlling house flies without relying solely on chemicals.