Strict requirements on the use of animal manures in fresh produce production imposed by the Food Safety and Modernization Act (FSMA) threatened to adversely impact the mushroom industry, which relies on horse and poultry manure for a specialized growth substrate. But a new study shows that heat generated during the traditional composting process — originally developed to kill insect and fungal pests of mushrooms — is adequate for eliminating human pathogens that might be present, according to researchers in Penn State's College of Agricultural Sciences.