Insecticidal, food utilisation and biochemical effect of essential oils extracted from seeds of Brassica juncea (Czern.) against Spodoptera litura (Lepidoptera: Noctuidae) (Fabricius)

The glucosinolate rich hot and cold hexane extracts of Brassica juncea had a negative effect on the development of Spodoptera litura larvae when they were fed on different concentrations of the extracts. Both larval growth index and pupal growth index declined with treatment. However the hot extract with 3-butenyl isothiocyanate as the predominant compound had a more deleterious effect as at 3125ppm the larvae were unable to complete their development. The nutritional indices too were more adversely affected with hot extract as compared to cold extract. The RGR, RCR, ECI and ECD declined significantly with increase in concentration of the hot hexane extract. The activity of antioxidant enzymes, SOD and catalase decreased while that of phosphatases, GSTs, phenol oxidases increased during the initial treatment duration but decreased on prolonged treatment of the larvae with LC50 concentration of hot extract. A similar trend was observed for glutathione and lipid peroxides but a decrease in ascorbate content was observed as compared to control. The findings reveal a toxic effect of 3-butenylisothiocyanate rich hot hexane extract of B. juncea on S. litura larvae

Effect of gallic acid on the larvae of Spodoptera litura and its parasitoid Bracon hebetor

Abstract The antibiosis effect of gallic acid on Spodoptera litura F. (Lepidoptera: Noctuidae) and its parasitoid evaluated by feeding six days old larvae on artificial diet incorporated with different concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm, 3125 ppm) of the phenolic compound revealed higher concentration (LC50) of gallic acid had a negative impact on the survival and physiology of S. litura and its parasitoid Bracon hebetor (Say) (Hymenoptera:Braconidae). The mortality of S. litura larvae was increased whereas adult emergence declined with increasing concentration of gallic acid. The developmental period was delayed significantly and all the nutritional indices were reduced significantly with increase in concentration. Higher concentration (LC50) of gallic acid adversely affected egg hatching, larval mortality, adult emergence and total development period of B. hebetor. At lower concentration (LC30) the effect on B. hebetor adults and larvae was non-significant with respect to control. Gene expression for the enzymes viz., Superoxide dismutase, Glutathione peroxidase, Peroxidase, Esterases and Glutathione S transferases increased while the total hemocyte count of S. litura larvae decreased with treatment. Our findings suggest that gallic acid even at lower concentration (LC30) can impair the growth of S. litura larvae without causing any significant harm to its parasitoid B. hebetor and has immense potential to be used as biopesticides