Evaluation of various fungicides and microbial based biocontrol agents against bird’s eye spot disease of tea plants

A field experiment was conducted to study the efficacy of six fungicides comprising contact, systemic and botanical fungicides and three biocontrol agents for the management of bird’s eye spot disease in tea plantations. Among 16 treatments, systemic fungicides were found to be superior to biocontrol agents in controlling the disease whereas the maximum green leaf yield was significantly increased in those applied with biocontrol agents. On the whole, Streptomyces sannanensis offered the maximum yield of 3998 kg ha⁻¹ made tea followed by Trichoderma harzianum (3884 kg ha⁻¹ made tea). Between the two different carrier materials evaluated for the application of biocontrol agents, vermicompost-based bioformulation showed better efficacy than talc-based formulation. Of the three (bacteria, fungi and actinomycetes) groups of biocontrol agents, S. sannanensis was better than Pseudomonas fluorescens and Trichoderma atroviride belonging to bacterial and fungal antagonists; respectively in terms of disease protection and increasing yield potential. Similarly, the biometric, physiological and biochemical parameters were also increased in plants greatly after imposing various treatments. Plucking surface of the bush, number of plucking points per unit area, internodal length, leaf moisture and dry matter contents were found higher in plots applied with biocontrol agents than those treated with fungicides. Almost all of the tea quality parameters such as total liquor colour, thearubigins, theaflavins, highly polymerized substance and caffeine were significantly improved in biocontrol treated plants. Theaflavin and thearubigin contents were increased in the range of 9.00–9.57% and 1.27–1.54% respectively in vermin based treatment. Similarly the amount of caffeine content (3.66–4.08%) and flavour index (4.18–5.31%) were considerably enhanced.