Effect of medicinal plant extracts on biological parameters of tobacco caterpillar, Spodoptera litura.

Aqueous extracts (1 &2%, dry wt. basis) from nine medicinal plant species viz., Jatropha curcas, Syzygium cumuni, Plantago ovata, Artemisia annua, Pogostemon pachouli, Stellaria media, Cinnamomum camphora, Cymbopogan winterianus and Cnicus benedictus were studied for their effect on feeding behavior, growth, development and survival parameters against 6 d old larvae of tobacco caterpillar, Spodoptera litura under laboratory conditions. All the plant species at 1% concentration reduced feeding in comparison of control (Mean leaf area consumed = 6.7cm2) except S. cumuni, which reflected a non-significant phagostimulant activity over control (6.8cm2). C. benedictus (2.1cm2) and J. curcas (3.5cm2) caused a significant reduction in larval feeding at p = 0.01. Plant extracts from two species viz., J. curcas (2%) and C. benedictus (1 and 2%) proved effective in reducing the larval weight gain at 2 days after feeding, though non-significantly. The same plants at both the concentrations caused a significantly higher mortality of the larvae, a significant reduction in pupal weight (g) and pupation (%) over control (0.31g and 100%). The data on larval mortality (13.3 and 16.6%), pupal weight (0.18g and 0.17g) and pupation (70 and 43.3%) as affected by J. curcas and C. benedictus (2% conc. each) respectively, indicated a significant impact on survival and developmental parameters of S. litura. It can be concluded that C. benedictus and J. curcas proved detrimental to the pest at both the concentrations.