Impact of Chemical Treatments on Microbial Contamination and Yield Performance of Pleurotus ostreatus

Mushroom mycelium is recognised as an important source of nutraceutical and pharmaceutical compounds because of its diverse bioactive constituents and therapeutic potential, while edible mushrooms are regarded as low-energy foods offering substantial nutritional and functional benefits due to their rich nutrient and bioactive composition. An experiment was conducted at the Mushroom Culture House and Plant Pathology Laboratory, Sher-e-Bangla Agricultural University, Dhaka, from April to October 2019 to evaluate the effects of different chemicals treated rice straw on the growth and yield of oyster mushroom (Pleurotus ostreatus) and to isolate associated contaminants. Five fungi—Sclerotium rolfsii, Trichoderma harzianum, Fusarium oxysporum, Penicillium sp., and Aspergillus niger—were identified. Treatments included hydrogen peroxide (10,000, 20,000, and 30,000 ppm), mancozeb (100 ppm), mancozeb+metalaxyl (100 ppm), bleaching powder (100 ppm), and wood ash (10,000 ppm). Among the treatments, 30,000 ppm hydrogen peroxide showed the highest inhibition of radial mycelial growth (72.41–93.46%), followed by mancozeb+metalaxyl (100 ppm). It significantly reduced days to mycelium running (16.80 days) and primordia initiation to first harvest (3.80 days), compared to the control (22.20 and 6.60 days, respectively). This treatment also produced the highest stipe length (5.17 cm), individual fruit weight (4.54 g), maximum yield (202.38 g), and biological efficiency (40.48%). Contamination increased from first to third flush, with maximum severity (68%) in control and 36% in ash-treated substrate at the third harvest. No contamination was observed in substrates treated with 30,000 ppm hydrogen peroxide and 100 ppm mancozeb+metalaxyl, indicating superior efficacy in managing competitor moulds and enhancing productivity.