An assessment of ecofriendly insecticidal toxicity of Ocimum sanctum, Croton tiglium and Zingiber officinale extractives against Bihar hairy caterpillar, Spilarctia obliqua Walker (Lepidoptera: Arctiidae)

Abstract

The Bihar hairy caterpillar, Diacrisia (Spilarctia) obliqua Walker are sporadic in nature has been in regular occurrence in northern Indo-Gangatic reigion, causing considerable damage to cruciferous crops and vegetables in our country. An experiment was conducted to test the insecticidal efficacy of six naturally occurring plant extracts against third instar larvae of Diacrisia (Spilarctia) obliqua Walker under the laboratory conditions. The bio-efficacy of six plant materials viz., Croton tiglium Linn., Datura alba Linn, Ocimum santum Linn, Spilanthes acmella Murr, Thavetia nerfolia Linn. and Zingiber officinale Linn. were prepared with the help of the soxhlet apparatus under the laboratory conditions and one untreated control used for detail study. The laboratory trial was done in three glass petridishes (10cm diameter and replicated thrice by using each selected extracts per petridish. To record the mortality of ten larvae of Spilarctia obliqua were released inside each pair of petridishes and allow them to remain for 24 hours. These petridishes were kept as such under control conditions and mortality count was taken after 6, 12, 24 hours of exposure. The result observed that O. santum registered highest mortality (65.61%) to the 3rd instars larvae of Spilarctia obliqua Walk. when compared to other plant extracts as; C. tiglium (57.39) >Z. officinale (55.84) >S. Acmella (51.70) >T. Nerfolia (51.56) >D. Alba (37.93), respectively. The aforesaid results have focused on natural plant products as alternatives for insect-pest control.