Relative toxicity of newer insecticides against lepidopteran pests of jute

摘要

Jute is one of the most important commercial crops of eastern Indian states of West Bengal, Assam, Bihar, Odisha and eastern Uttar Pradesh. It is an annual plant belonging to the family Malvaceae under the genus Corchorus. Only two species of jute arecultivated commercially viz., Corchorus olitorius L. (Tossa jute) and C. capsularis L. (White jute). Pest problem is one of the major constraints responsible for low productivity of jute as the crop is inflicted to damage by more than 40 species of pests from seedling stage to harvest of the crop which declines the yield as well as quality of fibres. About a dozen of important pests are reported of which, Bihar hairy caterpillar (BHC), Spilarctia obliqua Walker (Lepidoptera: Arctidae) during active growth stage and tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) during seedling stage are the most important pests occurring regularly and causing severe defoliation of the crop. Both the lepidopterans are polyphagous pests attacking many cultivated plant species. S. obliqua once considered as a sporadic pest has elevated to a status of major pest and severe outbreak of this pest during 2011 and 2012 in jute and sunnhemp cannot be overruled from considering it as a major pest of bast fibre crops (Satpathy et al, 2014). S. litura has attained the status of being resistant to many insecticides which has led to sporadic outbreaks of the pest and failure of crops (Ahmad etai, 2007). Chemical control stands as an integral part of any IPM strategy for effective management of any pest. It is inevitable for any pest to attain resistance within 2-3 years immediately after its advent in the commercial markets. With the widespread manifestation of insecticide resistance to major class of insecticides (organophosphates, carbamates and synthetic pyrethroids), it is essential to develop new molecules of insecticides with diversified modes of action (Sabry et al, 2014). Owing to the dense hairy nature of larva and resistance surge up by the pest (Dhingra et al., 2007), it has necessitated the evaluation of newer insecticide molecules with unique mode of actioncoupled with lower dosages. Hence, present study was undertaken to study the efficacy of certain newly released insecticides with diversified modes of action for the effective control of S. obliqua and S. litura in jute.