PHYTOCHEMICAL SCREENING AND PESTICIDAL EFFICACY OF PHYTOECDYSTEROID FRACTION OF A FERN PITYROGRAMMA CALOMELANOS (L.) LINK AGAINST SPODOPTERA LITURA (FABRICIUS.)

Abstract

Lepidopteran insect pests voraciously feed the vegetable crops and causes yield loss every year. Chemical insecticides widely used to control the destructive pest incidence which heavily affects the beneficial and non-target organisms and in the mean time, pests developed resistance. Biopesticides are being developed to minimize these ill effects. Plants synthesize secondary metabolites to prevent from biotic and abiotic stresses. More than 27 families of pteridophyta (ferns) are reported with phytoecdysteroids (PEs). PEs are analogues of insect moulting hormone and acts as insect growth regulators (IGRs). The present study aimed to isolate the phytoecdysteroid fraction from the fern, Pityrogramma calomelanos, preliminary screening of phytochemicals using standard protocols including UV-Visible spectrophotometric analysis and survival, growth and developmental periods of Spodoptera litura treated with phytoecdysteroid fraction. Steroids and phenolic compounds were present in the fraction and six prominent peaks were recorded between the wavelength of 200-800nm. Spodoptera litura larvae treated with phytoecdysteroid fraction showed maximum larval mortality (68%) in 2000ppm (LC50 = 1473ppm; F = 48.65; p = 0.049). Pupation, pupal weight and adult emergence were decreased in higher concentrations. Pupal mortality was relatively high in treated group than control (2.04%). Larvae treated with minimal concentrations exhibited developmental deformities includes larval - pupal, pupal -adult intermediates, deformed pupae, ecdysial failure, adultoids, early/late developmental periods and it may due to the interaction of phytoecdysteroid fraction to the insect endocrine system. Therefore, phytoecdysteroid mediated biopesticide formulation could be the better alternative to commercial chemical insecticides under IPM programme.