Role of Microorganisms in Sustainable Tea Cultivation in North East India: Recent Advances and Current Scenario

Abstract

Sustainable tea cultivation rely more on adopting alternative control strategies for effective tea pest management in an environment-friendly way which could replace some insecticides and thereby reduce the amount of pesticide residues in manufactured tea. Conservation of natural enemies and biodiversity of microorganisms in tea ecosystem is inevitable because, these natural enemies including the entomopathogens can play a vital role by providing effective control of target pests. With this background an attempt has been made to isolate Beauveria spp, and Metarhizium spp from Darjeeling and Dooars tea ecosystems of West Bengal, India and identified potential isolates like (BKN 1/14 and (MET 5/1) as Beauveria bassiana and Metarhizium anisopliae respectively. Stock suspension of BKN 1/14, MET 5/1 were prepared at concentration 1 × 108 CFU/ml, further diluted to 0.25%, 0.5%, 0.75% and 1% using distilled water were sprayed on different life stages of tea mosquito (Helopeltis theivora), as well as red spider mite (Oligonychus coffeae) respectively. A Baculovirus, belonging to the group Nucleopolyhedrosis Virus (NPV) which infects the Hyposidra talaca larvae has also been isolated, identified, and characterized. Based on the findings of the laboratory studies, these beneficial microbes were developed in to a 5% AS formulations with the support of an industry partner, following standard protocol. The developed 5% AS formulations were evaluated their field bio-efficacy under in vivo conditions following the Standard Operational Procedure (SOP) in three different locations against tea mosquito, red spider mite with encouraging results. The NPV was formulated in to an oil based suspension has also been tested at different concentration against tea lopper both under laboratory and field conditions with encouraging results in comparison to untreated control. All the three formulations were found to be non-phytotoxic to the tea plants, safer to the insect natural enemies, there is no tainting effect on made tea and were found to have a longer shelf life at room temperature without any change in their bio-efficacy. These strains could be commercialized after fulfilling the requirements for its registration and label claim on tea for the benefit of the tea industry.

Keywords: Microbial control; Entomopathogens; Tea pests; Beauveria bassiana; Metarhizium anisopliae Nucleopolyhedrosis Virus (NPV)