Formulation of plant based insecticides, their bio-efficacy evaluation and chemical characterization

Abstract

The aim of this study was to develop Emulsifiable Concentrate (EC) formulations from seed oils of Pongamia pinnata L., Pachyrhizus erosus L. and Annona squamosa L. Insecticidal efficacy of developed formulations was tested in-vitro against cabbage aphid (Brevicoryne brassicae L.) and in-vivo against aubergine aphid (Aphis gossypii G.) and whitefly (Bemisia tabaci G.). EC formulations comprising of seeds extract (40%) were prepared using bio-degradable solvents (50%) and emulsifier blends (10%) with hydrophilic-lypophilic balance (HLB) value (12.54) suitable for the seed oils formulation. Among nine EC formulations prepared from seed oils of each plant, EC-1 type performed well in terms of emulsion stability, cold test, accelerated storage and flash point test indicating feasibility for their commercial production. In-vitro study of A. squamosa 40 EC at 1% dose caused the maximum mortality of 80.7% (LC50 = 0.08%) against B. brassicae at 72 h after the treatment. The bio-efficacy was comparable with the synthetic insecticide dimethoate 30 EC at 0.1% dose. Besides A. squamosa, the 40 EC formulation of P. pinnata at 1% dose having 70.6% mortality at 72 h after treatment (LC50 = 0.19%) was also found promising. In-vivo studies in brinjal also indicated the maximum reduction of aphids (67.3–72.3%) and whiteflies (67.5–75.6%) within 5–14 days after application of A. squamosa 40 EC formulation at 1.0% dose followed by P. pinnata 40 EC. The total flavonoids and phenolic content in all the crude seed extracts varied from 20.9 to 53.9 mg QE/g and 5.8–9.5 mg GAE/g, respectively. Further analysis of the extracts by GC-MS revealed some bioactive constituents belonging to fatty acids, esters, aldehyde, phenols, etc. The study unveiled its significance in developing herbal insecticidal formulations as an alternative to harmful synthetic chemical insecticides and a step forward towards development of a promising eco-friendly technology in crop protection.