Molecular characterization of an Isaria fumosorosea (Wize) native strain, and its pathogenicity on Eublemma amabilis (Lepidoptera: Noctuidae)

Abstract

Background Eublemma amabilis Moore (Lepidoptera: Noctuidae) is an important pest of lac insect, Kerria spp. (Hemiptera: Tachardiidae: Coccoidea) causing up to 20–25% damage of lac and its encrustation, which has immense industrial utilities. Extensive field monitoring in Regional Lac Insect Field Gene Bank (RLIFGB) resulted in collection of a large number of naturally occurring entomopathogenic fungi (EPF) infected insect cadavers on the lac encrustation of host plant, Flemingia semialata. Pathogenicity test under laboratory conditions showed its efficacy on E. amabilis larvae. Molecular characterization of this EPF by 18S rDNA identified it as Isaria fumosorosea (Wize) (accession number, MH414514.1). Results Being a potent EPF, biological parameters viz., conidial density and sporulation were determined and its pathogenicity were evaluated against eggs, larvae and pupae of E. amabilis at different spore dilution under laboratory conditions. The highest mortality rates of larvae and pupae (96 & 72%) and (88 & 72%) were recorded at 107spore/ml both in dipping and spraying methods, respectively. The egg mortality, however, was recorded as 40 and 35% for both methods, respectively, at 107spore/ml, which was significantly lower than other stages of E. amabilis. Field study at (107 spore/ml) recorded 81.18, 59.41 and 76.36% mean population reductions over control during monsoon 2019, winter 2019–2020 and summer 2020, respectively. Biosafety analysis of the native EPF on productivity linked parameters of lac insect was found to be safe suggesting that the native Isaria fumosorosea (MH414514.1) strain, reported first from Assam. Conclusions In this study, it was confirmed that the EPF I. fumosorosea can be offered as an effective microbial agent, alternate to insecticide against E. amabilis, either as a stand-alone strategy or in an integrated approach.