Potential of the entomopathogenic fungus, Metarhizium anisopliae s.l. for control of red spider mite, Oligonychus coffeae Nietner on tea crop

ABSTRACT

The present study evaluates the pathogenic efficacy of an entomopathogenic fungus, Metarhizium anisopliae s.l. (=M. anisopliae) against the red spider mite, Oligonychus coffeae damaging tea plants. Laboratory studies revealed that M. anisopliae s.l. was pathogenic on O. coffeae and exhibited 78% mortality. Evaluation of formulated 5% aqueous suspension (AS) of M. anisopliae (1000 ml containing 2 × 107 conidia/ml in 400 L of water/ha) against O. coffeae through micro-plot study revealed a maximum of 68.2% reduction in mite’s population in sprayed plots, as compared to Fenpyroximate (5% EC), where a 67.5% reduction in mite’s population was recorded. Furthermore, large-scale field trials with aqueous suspension of entomopathogen revealed that 1000 and 1200 ml doses of M. anisopliae s.l. 5%AS each in 400 L of water/ha significantly reduced O. coffeae’s population in the tea gardens of Dooars and Darjeeling regions, India. Metarhizium anisopliae s.l. was more effective than standard acaricides and was non-pathogenic to the beneficial insects present in the tea gardens. Metarhizium anisopliae s.l. 5%AS had no phytotoxic effect on the tea leaves, with acceptable organoleptic attributes. Thus, M. anisopliae s.l. isolate can be commercialized as an alternative natural acaricide to reduce the load of synthetic acaricides in the tea crop.

KEYWORDS:

• Metarhizium anisopliae s.l.
• tea crop
• pathogenic activity
• Oligonychus coffeae
• biopesticides

Acknowledgements

Authors are thankful to the Biotechnology Industry Research Assistance Council (BIRAC) New Delhi-110003, Govt. of India, for the financial support rendered in the form of a Research Project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contribution

BD: Performed laboratory and field trials, analyzed and interpreted the data of the work and prepared the original manuscript. AB: designed and guided the laboratory as well as the field trials, reviewed and edited the writing. AKP: cultural and morphological characterization of entomopathogen, review and technical support. KCK: collected soil samples and isolated M. anisopliae s.l. AJP: finalized the protocol for the formulation of M. anisopliae s.l. HR and PD: assisted in conduction of field trials of M. anisopliae s.l. ELA and VRT: prepared M. anisopliae s.l. 5% AS liquid formulation. The authors read and approved the final manuscript.

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