In vitro Antagonism of Trichoderma Isolates and Efficacy of Chemical Fungicides against Mycelial Growth of Pestalotiopsis theae

Abstract

Grey leaf blight, one of the most important fungal foliar diseases of tea is caused by Pestalotiopsis spp. An in vitro study was conducted at Agriculture Research Station, Pakhribas to evaluate bio-efficacy of two Trichoderma isolates namely Trichoderma viride and Trichoderma harzianum using dual culture technique. Similarly comparative efficacy of five fungicides viz. Copper Oxychloride 50% WP, Carbendazim 50% WP, Metalaxyl 8% WP + Mancozeb 64 % WP, Carboxin 37.5% WS + Thiram 37.5% WS and Hexaconazole 5% EC at four different concentration of 50 ppm, 100 ppm, 200 ppm and 500 ppm was tested using poisoned food technique. The experiment was arranged in a completely randomized design with three replications for each treatment and a control. Trichoderma viride and Trichoderma harzianum exhibited 66.64% and 62.32% growth inhibition respectively against Pestalotiopsis theae. Growth inhibition by fungicides ranged from 35% to 100%. Hexaconazole exhibited complete mycelial growth inhibition (100%) regardless of concentration. This complete inhibition (100%) in colony growth was recorded at 200 ppm and 500 ppm of Carboxin + Thiram and then in Metalaxyl + Mancozeb at 500 ppm. While least (35.62%) inhibition on mycelial growth of P. theae was observed with Copper Oxychloride at 50 ppm. There was significant reduction in colony growth of P. theae with each treatment at all concentration in comparison to control. This study indicated significant results by fungicides even at lower concentration and by both Trichoderma spp. This study established Trichoderma spp as a successful alternative and hence recommends use of an integrated approach with both effective fungicides at low concentration and bio-control agents in further managing grey leaf blight of tea plant after subsequent field trials.