Phyto-toxicity of indian medicinal plants tinospora crispa (menispermaceae) and psidium guajava (myrtaceae) against tobacco cutworm, helicoverpa armigera (hub.) (lepidoptera: noctuidae)

Author: 
Elanchezhiyan K., GokulakrishnanJ., Deepa J.,and Balu Selvakumar

Helicoverpa armigera is highly polyphagous pest, infest more than 500 plant species and is a serious pest in India. The greatest damage is caused to cotton, tomatoes, maize, chick peas, alfalfa and tobacco etc. This notorious pest initially feeds on vegetative parts and subsequently on immature pods and ultimately causes severe loss of production. However, many chemicals available for treatment of insect pest are also toxic to natural enemies and gradually the pest will develop resistance to it. The objective of the present study was to evaluate larvicidal, ovicidal and oviposition deterrent activities of benzene, diethyl ether, ethyl acetate and methanol leaf extract of Tinospora crispa and Psidium guajava against Helicoverpa armigera. Twenty five early fourth instar larvae of Helicoverpa armigera was exposed to various concentrations and was assayed in the laboratory by using the protocol of Abbott’s formula (1925).; the 24h LC50 values of the Tinospora crispa and Psidium guajava leaf extract was determined by probit analysis. The ovicidal activity was determined against Helicoverpa armigera to various concentrations ranging from 75-450 ppm under laboratory conditions. The hatch rates were assessed 48hrs post treatment. For oviposition deterrent activity, ten pairs of (adult moths) H. armigera were introduced in individual cage. 10% (w/v) sucrose solution with multivitamin drops was provided for adult feeding to increasing fecundity, five replicates were maintained for control and treatments. After 48h, the numbers of eggs laid on treated and control leaves were recorded and the percentage of oviposition deterrence was calculated. The LC 50 value of benzene, diethyl ether, ethyl acetate and methanol leaf extracts of Tinospora crispa were 86.26, 89.55, 77.64 and 62.63ppm, respectively. Psidium guajava shows the LC50 values of 128.51, 132.64, 124.97 and 118.65ppm, respectively. Among two plant extracts tested, Tinospora crispa extracts were found to be most significant ovicidal activity 100% egg mortality (zero hatchability) observed at 300ppm and 375ppm for Psidium guajava. Methanol extract of Tinospora crispa and Psidium guajava showed 100% oviposition deterrency against the gravid moths of H.armigera at 200 and 240ppm concentration. In general, the oviposition deterrency is directly proportional to the increase in the concentration and also among the various extracts tested, methanol extract was found to have significant activity than the other solvent extracts. From the results it can be concluded the crude extract of Tinospora crispa and Psidium guajava were an excellent potential for controlling agricultural pest Helicoverpa armigera.