Abstract
Jute hairy caterpillar, Spilosoma (=Spilarctia) obliqua (Walker) (Arctiidae: Lepidoptera), is an irregular and polyphagous insect pest that occurs all over India. A severe natural viral epizootic was observed in the field population of S. obliqua in jute. The virus was characterized as Spilosoma obliqua nucleopolyhedrovirus (SpobNPV NBAIR1) based on morphological, biological, and molecular characterization. Under scanning and transmission electron microscopy (SEM and TEM), the occlusion bodies (OBs) of SpobNPV NBAIR1 appeared as both tetrahedral and triangular with the size ranged from 1.04-1.72 μm. The results on the bioassay studies revealed that the lowest LC50 value of 2.93 OBs/mm2 by leaf disc bioassay against the second instar S. obliqua showed its high virulence. The identity of SpobNPV was further confirmed by the amplification of polyhedrin gene (NCBI GenBank accession no. MK288145). Eleven species of lepidopteran insects, viz., Spodoptera litura, S. exigua, S. frugiperda, Helicoverpa armigera, Plutella xylostella, Amsacta albistriga, Maruca vitrata, Trichoplusia ni, Pieris brassicae, Agrotis ipsilon, and Bombyx mori, were not susceptible to the infection with SpobNPV NBAIR1. Field experiments on jute crop revealed 68.92, 78.59, and 93.16% reduction in larval population of S. obliqua at 3, 4, and 7 days post spray of SpobNPV NBAIR1 (1.5 × 1012 OBs/ha at 2 ml/l), respectively. The present study is a renewed effort in the management of S. obliqua by the new strain of SpobNPV NBAIR1.
Highlights
Jute hairy caterpillar, Spilosoma (= Spilarctia) obliqua (Walker) (Arctiidae: Lepidoptera), is an important polyphagous insect pest broadly distributed across India (CPC 2004)
The present study aimed to evaluate the efficacy of nucleopolyhedrovirus (SpobNPV NBAIR1) for the management of S. obliqua on jute crop under field conditions
Discharged body fluid was observed under a phase-contrast microscope which revealed that a large number of spherical particles resembling as baculoviral occlusion bodies (OBs)
Summary
Spilosoma (= Spilarctia) obliqua (Walker) (Arctiidae: Lepidoptera), is an important polyphagous insect pest broadly distributed across India (CPC 2004). It damages about 126 plant species including pulses, oilseeds, cereals, vegetables, mulberry, turmeric, and fiber crops (jute, mesta, and ramie) that. Viral bio-control agent has been recognized as inherently less toxic, eco-friendly than conventional chemical pesticides (Gramkow et al 2010). Their use as a biological pest control agent has been greatly encouraged with assumed comparative advantage as fastidious host-specific organisms (Gramkow et al 2010). In the present pest management scenario compared to the chemical method of pest control, the use of baculoviruses is a relatively cheap, practicable, environmental friendly, and potent tool for management of insect pests of agricultural importance of farm crops
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