Vol. 12, Issue 12 (2023)

Author(s):
M Visalakshi, Arunkumar Hoshamani, A Kandan, P Kishore Varma, B Bhavani and R Sarita

Abstract:
Metarhizium (Nomuraea) rileyi was isolated from cadavers of maize fall armyworm (FAW), Spodoptera frugiperda noticed in epizootic form at Regional Agricultural Research Station (RARS), Anakapalli, Andhra Pradesh in the month of October, 2019. M. rileyi ANGRAU Anakapalli strain (AKP Nr-1) sequence was submitted to NCBI and accession number (MN 960559) was retrieved in 2020. Laboratory bioassay studies of the indigenous entomofungal strain, M. rileyi (ANGRAU AKP Nr1) against 2^rd instar larvae of the S. frugiperda were conducted for three years from 2020 to 2022. Among the different concentrations tested, M. rileyi (ANGRAU AKP Nr1) @ 1 x109 spores/ml caused highest larval mortality (92.54% and 92.24%) followed by 1x108 spores/ml with 87.87% and 89.58% larval mortality in leaf dip method and larval treatment method respectively. M. rileyi (ANGRAU AKP Nr-1) showed LC50 of (1.1 x108 spores/ml) and LT50 (1 x108 spores/ml) as 84.4 hours. Field efficacy studies of two indigenous entomofungal strains of M. rileyi (ANGRAU, Anakapalle strain and UAS, Raichur strain) against FAW conducted under ICAR-AICRP on Biological control centres located at RARS, Anakapalle (ANGRAU) and UAS, Raichur during 2020-21 to 2022-23. Native isolate, M. rileyi (ANGRAU AKPNr-1) at concentration 1x108 spores/ml @ 5 g/L as two sprays was effective with significantly low fall armyworm incidence (7.45% and 4.83%) followed by M. rileyi (UAS, Raichur strain) (11.46% and 4.82%) compared to high fall armyworm incidence in untreated control (28.22 % and 18.01%) in 2020 and 2021 respectively. Evaluation studies of native isolates of entomopathogens as three sprays against maize FAW conducted in 2022 showed very low FAW damage in chemical treatment, emamectin benzoate (2.05%) followed by M. rileyi (ANGRAU strain AKP-Nr-1) (3.88%) and M. rileyi (UAS, Raichur strain) (4.69%) compared to high damage in Untreated control treatment (20.85%). Percent reduction in fall armyworm damage over control was high in M. rileyi Anakapalle strain (65.87%) and M. rileyi Raichur strain (63.18%) as effective treatment after the chemical insecticide, Emamectin benzoate (87.44%). Cob yield recorded significantly high in M. rileyi ANGRAU Anakapalle strain (63.22 q/ha) and UAS, Raichur strain (58.22 q/ha) after chemical, emamectin benzoate (69.3 q/ha) and low in untreated control (35.04 q/ha). Yield increase over control in M. rileyi (Anakapalle strain) and M. rileyi (UAS, Raichur strain) were 66.83% and 66.15 % respectively compared to 74.37% in Chemical insecticide, Emamectin benzoate with effective against fall armyworm in maize crop .