MICROBIAL CONTAMINATION IN OYSTER MUSHROOM (Pleurotus ostreatus) AND THEIR MANAGEMENT USING DIFFERENT CHEMICALS

Abstract

An experiment was carried out to find out the effect of different chemicals treated rice straw on the growth and yield of oyster mushroom (Pleurotus ostreatus) and to isolate contaminants associated with Pleurotus ostreatus. Total 5 fungi namely Sclerotium rolfsii, Trichoderma harzianum, Fusarium oxysporum, penicillium sp. and Aspergillus niger were isolated and identified. Three different concentrations namely 10000, 20000, 30000 ppm of hydrogen peroxide, 100 ppm of mancozeb, 100 ppm of mancozeb+metalaxyl, 100 ppm of household bleaching powder and 10000 ppm wood ash were used to manage the contaminated fungi. Among the tested chemicals, higher inhibition of radial mycelial growth was observed with 30000 ppm hydrogen peroxide followed by Mancozeb+Metalaxyl (100 ppm). The maximum days (22.20 days) required for mycelium running was recorded from control whereas the minimum days (16.80 days) found under 30000 ppm hydrogen peroxide. The maximum days (6.60 days) required for primodia initiation to 1 ii

st harvest was observed from control whereas lowest days (3.80 days) was observed under 30000 ppm hydrogen peroxide. 30000 ppm hydrogen peroxide showed significantly best performance with the total number of fruiting body and yield per spawn packets. The highest length (5.17 cm) of stipe was recorded from 30000 ppm hydrogen peroxide. Number of fruiting body/packet of oyster mushroom showed statistically significant differences due to use different chemicals for substrate sterilization. The maximum weight (4.54 g) of individual fruiting body was recorded from 30000 ppm hydrogen peroxide which was closely (4.06 g) followed by 20000 ppm hydrogen peroxide and the minimum weight (2.36 g) was found in control. Inhibitory effect against the growth competitor moulds ranged between 72.41-93.46%, maximum yield (202.38 g) and maximum biological efficiency (40.48%) obtained from 30000 ppm Hydrogen peroxide treated packets. Percent contamination of fungi gradually increased from 1 stage to 3 rd flash stage. Maximum severity of contamination 68% was observed in control and 36% in ash treated substrate at 3 rd harvest. In other cases the spawn packets were free from contamination when the substrate was treated with 30,000 ppm hydrogen peroxide and 100 ppm mancozeb+metalaxyl.