Bio-efficacy of chloroform crude extracts of chick weed Ageratum conyzoides (Linn.) against the tobacco cutworm Spodoptera litura (Linn.) and their non-toxicity against the beneficial earthworm

Abstract

The current study investigates the phyto-chemical screening of chloroform crude extracts of chickweed Ageratum conyzoides (Linn.) (Cm-Ac) and their target and non-target toxicity against the pest Spodoptera litura and beneficial earthworm. Phyto-chemical characterization of Cm-Ac over GC-MS technique revealed thirty four bio-active compounds with highest peak area% observed in Phenol, 2,4-Bis-(1,1-Dimethylethyl)-(6.340 PA%), followed by n-Hexadecanoic acid (5.95 PA%) and 1- Octadecene (5.94 %) respectively. Larval toxicity was observed maximum at the dosage of 1000 ppm at second instar (98.23 %) as compared to other dosages. Lethal dosage (LC50) obtained on 2.467 log ppm respectively. The sub-lethal toxic dosage of Cm-Ac (100–500 ppm) displayed adverse impact on larval-pupal growth and development in dose dependent manner. Also, the sub-lethal dosage of Cm-Ac also decreased the level of mid-gut enzymes in dose dependent manner. The mid-gut tissues including Gut Lumen-(GL), Epithelial Layer-(EL), and Brush Border Membrane-(BBM) severely affected at the prominent concentration of 500 ppm as paralleled with control. Non-target activity against Eudrilis eugeniae revealed that the Cm-Ac treatment is less toxic at the prominent concentration of 1000 ppm as paralleled to Cypermethrin treatment. Overall, the current results are promising in developing botanical based insecticides which are bio-degradable and importantly harmless or less toxic to the non-target earthworms.