Stem rot on banana is the latest and economic important disease to Jaffna; Sri Lanka, because of this infection, immediate control measure need through chemical application that’s why this research study was carried out as invitro condition against the fungal pathogen. Five broad spectrum contact fungicides at two levels of concentrations as manufacture recommended level and half of the recommended level were evaluated, using poison food technique, radial growth of mycelia of Basidiomycetes fungus Marasmiellus sp. (Agaricales: Tricholomataceae) isolated from Banana. It was observed that the fungicides Coblite (Copper 50% (w/w) WP as copper oxychloride), Pomarsol forte WP 80% (thiram 80%), Captan (Captan 50% (w/w) WP), Ridoaxyl (Metalaxyl 8 % (w/w) +Mancozeb 64% (w/w) WP), Max (Chlorothalonil 75% (w/w) WP)) at all the concentrations tested inhibited mycelial growth of the fungus. All fungicides significantly differed from the control except coblite. The highest percentage inhibition was recorded as 86.76% (11.92 mm Mean Colony Diameter (MCD)) from the manufacture recommended level of concentration (0.5g/100ml) of Metalaxyl 8% (w/w) + Mancozeb 64% (w/w) WP indicating combined effect of two compatible fungicides, followed by Chlorothalonil at both concentrations 0.15g/100ml and 0.075g/100ml were inhibited 64.09% (32.32 mm MCD) and 61.02% (35.08 mm MCD) of colony growth respectively, This investigation revealed that, Mancozeb and Metalaxyl in combination and Chlorothalonil based fungicides can be the best option for effective control of Marasmiellus sp.
