Abstract
With a view to develop an ecofriendly botanical pesticide, we evaluated the bioefficacy of crude extracts of Couroupita guianensis against third instar larvae of Helicoverpa armigera. Maximum feeding deterrency (81.67%) and least LC50 (2.72%) for larval mortality were seen in hexane extract. Hexane extract was subjected to column chromatography using different ratio of hexane-ethyl acetate solvent system. Totally eight fractions were collected. The fractions were screened at 125, 250, 500 and 1,000 mg/kg concentrations against H. armigera using no-choice leaf disc method. Fraction eight showed maximum antifeedant (86.24%) and larvicidal (80.88%) activities at 1,000 mg/kg concentration. C. guianensis could be utilized in pest control programme.
Highlights
In the last five decades, many countries including India have concentrated on non-polluting and economic entomological technologies to increase the productivity of vegetable crops and economically important trees
The present study revealed that maximum antifeedant activity of 81.67% was recorded in hexane leaf extract of C. guianensis at 5.0% concentration followed by chloroform (73.68%) and ethyl acetate (69.70%) extracts (Table 2)
Maximum antifeedant activity of 86.24% was noticed in fraction 8 at 1,000 mg kg–1 concentration (Table 3)
Summary
In the last five decades, many countries including India have concentrated on non-polluting and economic entomological technologies to increase the productivity of vegetable crops and economically important trees. Insect pests play a major role in damaging the crops and there is a need to use efficacious control agents. In the last few decades, the repeated use of synthetic chemicals to manage these pests has lead to their resurgence and outbreak, resistance to insecticides, elimination of existing natural enemies and pollution of soil, water, air and food (Patel et al, 1992). Prakash and Rao (1997) observed that plant pesticides do not contribute to resistance development or pest resurgence; nor do they cause negative effects on non-target organisms. They do not affect plant growth, seed viability and food quality but possess insecticidal, repellent, antifeedant and/or growth regulatory activities.
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