Biocontrol efficiency of Trichoderma asperellum in managing branch canker disease of tea (Camelia sp.), its effect on vegetative growth, natural enemies and phytotoxicity

An Indigenous Trichoderma asperellum strain was isolated from the tea soil of Nagrakata, situated in Dooars region of West Bengal. Its liquid suspension was evaluated under field conditions at different locations in Assam, Darjeeling and Dooars for two seasons for the management of branch canker disease. Its effect on vegetative plant growth, natural enemies and phytotoxicity was also studied. Among seven treatments, there were four concentrations of T. asperellum in comparison with T. harzianum (market sample), copper oxychloride, and untreated control. Findings of the investigation showed that the disease protection level was the highest when indigenous Trichoderma was applied at a concentration of 1600 ml per hectare. The disease protection level was 4.06–4.28, 4.65–4.90 and 4.12–4.40 in Assam, Darjeeling and Dooars, respectively. It promoted vegetative growth in terms of increased green leaf yield. The same concentration could produce higher made tea per hectare as compared to untreated control. In the Assam it was 2227 and 2260 kg as compared to 1986 and 2015 kg in untreated control during the first and second year, respectively. In Darjeeling, it was 390 and 438 kg against 347 and 390 kg in control; similarly, in Dooars it was 1787 and 1840 kg against 1592 and 1640 kg per hectare in the first and second year, respectively. The tested antagonist was safe for Chrysoperla carnea and Oxyopes javanus without having phytotoxicity on tea plants. It is concluded that the native antagonist could be a promising option for the management of canker disease, especially for organic tea gardens.