Journal of Environmental Biology

Evaluation of pathogenicity of indigenous entomopa-thogenic nematodes (Steinernematidae and Heteror-habditidae) from Mizoram, India, against tobacco cutworm, Spodoptera litura (Fabricius, 1775) 

H.C. Lalramnghaki^1,2, H.T. Lalremsanga², Vanramliana¹, Lalramliana¹*, Vanlalhlimpuia³ and S. Lalliansanga⁴ 

¹Department of Zoology, Pachhunga University College, Aizawl-796 001, India

²Department of Zoology, Mizoram University, Aizawl-796 004, India

³Department of Environmental Science, Aizawl-796 004, India

⁴Directorate of Agriculture (Research & Extension), Aizawl-796 001, India

*Corresponding Author Email : lrl_zoo@yahoo.co.in

Paper received: 21.12.2019 ?????? ???????????????????????????????????????Revised received: 05.07.2020 ???????????? ?????????????????????????????????????Accepted: 10.07.2020

Abstract

Aim: To evaluate pathogenicity of locally isolated entomopathogenic nematodes Heterorhabditis indica, Heterorhabditis baujardi and Steinernema sangi against larvae of S. litura (Lepidoptera: Noctuidae).

Methodology: Different concentrations of nematodes (10, 25, 50, 100, 200, 400 and 800 infective juveniles per larva) of H. indica, H. baujardi and S. sangi were used against 3^rd, 4^th and 5^th instar larvae of S. litura using Petri dish assay. Pathogenicity test was performed by assessing larval mortality of S. litura, penetration of infective juveniles and successive production of nematodes on the larvae of S. litura. LC₅₀ and LT₅₀ values were calculated by Probit Regression Analysis using SPSS software 20.0.            

Results: All the tested EPN isolates showed high pathogenicity against the pest, with a strong positive correlation between nematode concentrations, inoculation time and larval mortality. Among the isolates, S. sangi showed highest pathogenicity against the pest by showing the lowest value of LC₅₀ at 48 hr post?inoculation (9.2, 55.58 and 350.65 infective juveniles for 3^rd, 4^th and 5^th? instar larvae, respectively) and LT₅₀ values (24.52, 34.13 and 74.69 hr against 3^rd, 4^th and 5^th instar larvae, respectively) at a dosage of 50 infective juveniles per larva. Besides, the nematodes were produced successfully inside the 5th instar larvae of S. litura (57192.86 infective juveniles per larva for S. sangi and 72231.13 infective juveniles per larva for H. baujardi).      

Interpretation: EPN isolates represent good candidates to control S. litura and can be considered for integrated pest management (IPM).  

Key words: Biological control, Entomopathogenic nematodes, Infective juveniles, Integrated pest management, Spodoptera litura

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