In the present study, the essential oil from seven common spices, Anethum graveolens, Cuminum cyminum, Illicium verum, Myristica fragrans, Nigella sativa, Piper nigrum and Trachyspermum ammi was isolated and its insecticidal, oviposition, egg hatching and developmental inhibitory activities were determined against pulse beetle, Callosobruchus chinensis. Essential oils were isolated by hydrodistillation method using Clevenger apparatus. These essential oils caused death of adults and larvae of Callosobruchus chinensis when fumigated. The 24-h LC 50 values against the adults of the insect were 8.9 ml, 10.8 ml, 11.0 ml, 12.5 ml, 13.6 ml, 14.8 ml and 15.6 ml for N. sativa, A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi oils respectively. On the other hand, against larval stage these values were 6.4 ml, 7.9 ml, 8.9 ml, 11.1 ml, 11.7 ml, 12.2 ml and 13.5 ml for N. sativa, A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi respectively. These essential oils reduced the oviposition potential, egg hatching rate, pupal formation and emergence of adults of F 1 progeny of the insect when fumigated with sublethal concentrations. These essential oils also caused chronic toxicity as the fumigated insects caused less damage to the stored grains. The essential oil of N. sativa was found most effective against all the different stages of the Callosobruchus chinensis followed by A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi oils. All the responses were found concentration-dependent. The toxic and developmental inhibitory effects may be due to suffocation and inhibition of various biosynthetic processes of the insects at different developmental stages.

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Extracts of Capparis decidua stems and flowers showed insecticidal and oviposition inhibitory activities against Bruchus chinensis. The LC50 values of these extracts were found to increase with the increase in the polarity of the extract at different exposure periods. For instance, after 96 h, the LC50 values were found to be 3.619, 7.319, and 10.151 microg for CD1, CD2, and CD3, respectively. Extract CD7 was effective only at higher doses. The toxicity was found to be dose- and time-dependent. The females laid lesser number of eggs, when exposed to sublethal doses of different extracts and pure compounds, as compared to control. The maximum oviposition deterrence index was found for extract CD1 followed in decreasing order by CD2, CD3, and CD7. From extract CD1, two compounds were isolated and characterized as triacontanol (C1) and 2-carboxy-1,1-dimethylpyrrolidine (C2). When the females were exposed to sublethal doses of these compounds, they laid lesser number of eggs as compared to the control. C2 was found to have a slightly greater oviposition inhibition effect than C1. From fraction CD7, one novel compound labeled as CDF1 has been isolated and identified as 6-(1-hydroxy-non-3-enyl)tetrahydropyran-2-one. CDF1 has also shown insecticidal and oviposition inhibitory activities against B. chinensis at low concentrations.

Essential oil from Allium sativum was isolated and investigated for its repellent, insecticidal, ovipositional and egg hatching inhibition activities against pulse beetle, Callosobruchus chinensis (Coleoptera: Bruchidae). A. sativum essential oil repelled bruchid adults at a very low concentration in choice oviposition assay. A. sativum essential oil caused both fumigant and contact toxicity in C. chinensis adults in a concentration dependent manner. Oviposition potency of C. chinensis adults was reduced significantly when sublethal concentrations of A. sativum essential oil were applied by fumigation and contact method. In chronic toxic-ity assay, A. sativum essential oil reduced F1 progeny emergence, damage and weight loss in seeds. Findings of the present study suggest that A. sativum essential oil can be useful as promising agent in insect pest management programme.