Evaluation of microbial insecticides against leaf folder, Cnaphalocrocis medinalis Guen. infesting paddy

Abstract

A field experiment was conducted at Main Rice Research Station, Anand Agricultural University, Anand (Gujarat) during kharif-2009, 2010 and 2011 to assess the effect of eight microbial insecticides viz., Bacillus thuringiensis (Bt) @ 1.0 kg/ha, B.t. @ 1.5 kg/ha, Beauveria bassiana @ 1.0 kg/ha (cfu 2 x 106), B. bassiana @ 1.5 kg/ha, Verticillium lecanii @ 1.0 kg/ha(cfu 2 x 106), V. lecanii @ 1.5 kg/ha, Nomuraea rileyi @ 1.0 kg/ha, N. rileyi @ 1.5 kg/ha and recommended insecticide (Cartap hydrochloride 0.05 %) against leaf folder, Cnaphalocrocis medinalis Guen. infesting paddy. Results revealed that both the treatments of B. bassiana (higher and lower dose) exhibited leaf damage at par with chemical insecticide. Spider population in untreated plots registered maximum as compared to treated plots. Highest grain yield was harvested from the plots treated with chemical insecticide followed by N. rileyi @ 1.5 kg/ha. All the treatments of microbial insecticides were found at par with respect to fodder yield. Economics of different treatments showed that maximum Incremental Cost Benefit Ratio (ICBR) (1:48) was registered in the treatment of V. lecanii @ 1.0 kg/ha followed by B. bassiana @ 1 and 1.5 kg/ha. Though the treatments of N. rileyi exhibited relatively higher ICBR but it failed to suppress the pest effectively.