By C. M. Senthil Kumar, T. K. Jacob and S. Devasahayam
Increasing awareness about the ill-effects of large-scale use of chemical pesticides for the management of insect pests of agricultural crops has prompted scientists to develop alternative strategies for their management. The situation is more relevant in spice crops which are export-oriented earning valuable foreign exchange for the country. Fungi that cause diseases in insects (entomopathogenic fungi) have always fascinated entomologists as some fungi cause epizootics in insects, wiping out large proportions of their natural populations. Attempts are being made all over the world to discover new fungi and develop them into biopesticides that are safer and environmentally friendlier than chemicals. Fungi belonging to the genus Metarhizium (green muscardine fungi) are of special interest due to their worldwide occurrence, biological control potential and genetic diversity. Several commercial products are available world over based on this fungus.
Despite the varied soil and agroclimatic conditions across the country, only one species of Metarhizium (M. globosum) has been earlier reported from India. While surveying for the occurrence of entomopathogenic fungi on various spice crop pests in South India, we came across a species of Metarhizium causing epizootics in leaf hopper (Busoniomimus manjunathi), a serious pest of Malabar tamarind or Brindle berry (Garcinia gummi-gutta), an evergreen spice tree known for its culinary and medicinal properties. The fungus infected both adults and nymphs of the leafhoppers resulting in their death and mummification. The fungus was found to cause more than 60% mortality in field collected leaf hoppers. Morphological and multi-gene sequence data analysis indicated that the fungus was a new species and was named as Metarhizium indicum sp. nov., indicating its Indian origin.
Though over 27,000 fungal species are reported from India which represents one third of the global fungal diversity, taxonomic work on entomopathogenic fungi, especially those belonging to that Metarhizium lineage is very limited. Except for a lone report of M. globosum as a new species from India, the other fungi of this lineage reported from India are M. anisopliae, M. pingshaense and M. rileyi. This further underscores the need for rigid taxonomic re-evaluation of the reported species using molecular tools and to intensity explorations for identifying the hidden diversity of Metarhizium in the country. The findings are published in the latest issue of Journal of Invertebrate Pathology.
Further Reading
Senthil Kumar CM, Jacob TK, Devasahayam S, Rajeshkumar KC, Lad SS, D'Silva S, Geethu C. 2023. Metarhizium indicum, a new species of entomopathogenic fungus infecting leafhopper, Busoniomimus manjunathi from India. Journal of Invertebrate Pathology, 198:107919. https://doi.org/10.1016/j.jip.2023.107919
Dr C. M. Senthil Kumar is a Principal Scientist (Entomology) at ICAR-Indian Institute of Spices Research, Kozhikode, Kerala. Drs. T. K. Jacob and S. Devasahayam are former Entomologists from ICAR-Indian Institute of Spices Research, Kozhikode, Kerala.
Dr. C. M. Senthil Kumar can be contacted at: cmsenthil@gmail.com
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