Evaluation of some medicinal plant extracts, novel molecules and conventional agrochemicals for their efficacy against Spodoptera litura (Fabricius)
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Date
2010-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Present investigation was undertaken to evaluate the medicinal plants, novel molecules and conventional agrochemicals against Spodoptera litura (Fab.) All the experiments were conducted in Laboratory of the Department of Entomology at room temperature. The culture of the test species were maintained in the lab. on castor leaves. In the antifeedancy experiment with eleven medicinal plant extracts viz., Jatropha curcas, Syzygium cumuni, Ocimum basilicum, Artemisia annua, Azadirachta indica, Melia azedarach, Murraya Koenigii , Vitex negundo , Terminalia arjuna Phyllanthus emblica and Putranjeev roxburghii at 5% concentration against 7d old larvae of S. litura, high feeding deterrent property was exhibited by Syzygium cumuni with feeding inhibition of 70.83% followed by Azadiracta indica (51.38%) and Melia azedaraca (43.27%). In case of larval mortality (2DAF) the extracts of Azadirachta indica at both the concentrations (5% and 10%) caused 6.67% and 46.67% mortality and proved to be the most toxic among all the medicinal plants species tested. At 5% concentration of Azadirachta indica and Melia azedarach only 46.67% and 56.67% pupation was observed. Adult emergence percent was significantly reduced by all the plant extracts at both (5% and 10%) concentrations. In the present investigation the sensitivity of synthetic pyrethoids, neonicotinoids, organophosphates and novel molecules was studied against 7 days old larvae of S. litura. Among organophosphates chlorpyriphos was found to be 0.998 to 2 times more toxic than endosulfan between 24-72 h. The LC50 values of quinalphos, dichlorvas, chlorpyriphos, profenophos, triazophos and endosulfan at 24h were 0.111, 0.121, 0.0963, 0.156, 0.158 and 0.0962 % respectively. Among all the tested synthetic pyrethroids and neonicotinoids, lamdacyhalothrin was the most toxic with LC50 0.026%, followed by bifenthrin (0.028%), thiamethoxam (0.266%) and imidacloprid (0.327) at 24 h. Among the novel molecules indoxacarb was found to be the most toxic with LC50 value of 0.0019% followed by flubendamide (0.011%), spinosad (0.0264%), fipronil (0.079%) and cartap hydrochloride (0.126%) at 24 h. In another experiment different concentrations of fungicides, plant growth regulators and formulations of Bacillus thuringiensis were tested against S.litura by artificial diet incorporation method. Newly emerged larvae of S. litura were released on these test diets. Among fungicides Dithane M-45 caused complete larval mortality within 5 days and 7 days of feeding at higher concentration of 1.0 and 0.5 percent respectively while Bayletan showed no adverse effect on S.litura. A marked increase in larval period was recorded in all four fungicides. A gradual decrease in growth and success indicies was noticed with the increase in levels of these fungicides in the diet. In case of plant growth regulators gradual reduction in larval survival was recorded with increase in the levels of Miraculan and Gibberellic acid in the diet. Growth and success indices showed the similar trend. However lihocin failed to show any adverse effect on the growth and development of S.litura. Different levels of two B.thuringiensis formulations (Dipel and Halt) were also investigated using diet incorporation method. Complete larval mortality occurred within two days where larvae were reared on diets containing 500ppm of halt whereas in case of dipel complete larval mortality was recorded at 500ppm and 250ppm after 12 and 15 days respectively. A prolonged larval period was observed in diets fortified with B.thuringiensis formulation but no adverse effect on pupal period was recorded. Growth and development of this insect was suppressed by both the formulations.
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Thesis-PhD
Keywords
medicinal plants, plant extracts, molecules, agricultural chemicals, Spodoptera litura