Short communication
Azariah Babu
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 x 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 (Oligonychuscoffeae) 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 microbial were developed in to a 5% AS formulations by the 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 nonphytotoxic 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. Key words: Microbial Control, Entomopathogens, Tea Pests, Beauveria bassiana, Metarhizium anisoplae Nucleopolyhedrosis Virus (NPV) INTRODUCTION Tea (Camellia sp) is an economically important, perennial plantation crop and requires warm humid climate for adequate growth and production. Such perennial nature, coupled favorable micro as well as macroclimate for flourishing of different insect pests and fungal diseases, which together cause huge crop loss in terms of quantity and quality. Synthetic agrochemicals have been used since long back to get rid of these enemies. Although, these synthetic chemicals provide better control of insect pests for a longer period; their recurrent and imprudent usage invite numerous additional problems associated with such as, environmental pollution, pesticides resistance, resurgence of secondary pests etc., (Babu and Muraleedharan, 2010, Roy et al, 2011). The biological control agents (BCAs) like species of Beauveria, Metarhizium and a Baculovirus, belonging to the group Nucleopolyhedrosis Virus (NPV) are safer and promising components of integrated pest management programme (IPM), which have been adopted in various crops including tea for control of insect pests a (Papavizas, 1985, Roberts & St. Leger, 2004; Rehner & Buckley, 2005, Hall & Papierok,1982). In Darjeeling and other tea growing area of West Bengal, different liquid and wettable powder (WP) formulations of such beneficial fungi are already in practice since last several decades, however they are outsourced ones. Although; inWest Bengal, research work has been done in this direction (Debnath, 1986, Debnath, 1996, Babu and Kumhar, 2013, 2014) under lab conditions. A very little information on commercialization of such fungi is available. Our present study aimed at the isolation of B. bassiana and M. anisopliae, a Baculovirus (NPV) and development of suitable formulations for in vitro as well as in vivo evaluation against targeted insect pests.