Bioefficacy and persistence of botanicals against insect pests on cauliflower

Abstract

newline Supercritical fluid extracts of eupatorium, melia and sarcococca were screened through technique-A (dry powder of botanicals replaced at every pressure) and technique-B (same dry powder used at subsequent pressures) at different pressures under laboratory for insecticidal activity. The higher insecticidal activity as well as extract yield were obtained using technique-A. The eupatorium extract obtained at 125 bar (LC50: 0.0055, 0.0040, 0.0004%) and melia (LC50: 0.0078, 0.0035, 0.0038%) and sarcococca (LC50: 0.0085, 0.0057, 0.0082%) at 100 bar pressure were found effective against B. brassicae, P. brassicae and P. xylostella, respectively and selected for the study on field evaluation against insect-pests of cauliflower, persistent toxicity and relative safety to predators. Based on different mode of entry of botanicals, the contact toxicity of azadirachtin was found to be the maximum followed by eupatorium extract. On the basis of stomach and both stomach and contact action, azadirachtin was highly efficacious followed by melia extract. Maximum antifeedancy was observed in azadirachtin (AC50: 0.0001, 0.0002%) followed by melia (AC50: 0.0078, 0.0107%), eupatorium (AC50: 0.0106, 0.0183%) and sarcococca (AC50: 0.0127, 0.0185%) against P. brassicae and P. xylostella. Similar trend was followed for repellent effect. Studies on variation in the insecticidal activity of eupatorium in different seasons and melia extract obtained from different drupe stages revealed that eupatorium extract of old leaves collected during summer and autumn season and melia extract of unriped drupes possessed maximum insecticidal activity. Bioefficacy studies conducted during three cropping seasons (2012-13 to 2014-15) at Experimental farm of Department of Entomology, CSK HPKV, Palampur revealed that among botanicals, azadirachtin (0.00045%) and melia (0.06%) were found most effective against all the tested insects and statistically at par with cypermethrin (0.01%). The order of effectiveness based on persistent toxicity value