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Both seed and root extracts of the medicinal plant, Ashwagandha, Withania somnifera exhibit insect growth regulatory activity against the polyphagous pest, Pericallia ricini. Topical administration of W. somnifera seed and root extracts to last instar larvae of P. ricini disrupted moulting and metamorphosis, leading to a number of developmental abnormalities such as delay in larval-pupal and pupal-adult ecdysis, formation of larval-pupal, pupal--adult and larval-pupal-adult mosaics/chimeras, ecdysial failure, suppression of pupation and adult emergence and formation of abnormal pupae and adultoids. The treatment with seed extracts was more severe than that of root extracts as it completely suppressed the pupation and adult emergence. The results clearly suggest that the medicinal plant, W. somnifera acts as a potential insect growth regulatory (IGR) disrupting the moulting and metamorphosis as a consequence of interference with the endocrine system.

Background: The lepidopterans, Spodoptera litura and Pericallia ricini, are polyphagous pests of agricultural importance. The unscrupulous and non-judicious use of chemical pesticides for controlling the insect pests has resulted into severe environmental hazards, threatening non-target organisms and human health. Results: Administration of seed and root extracts of a medicinal plant, Ashwagandha (Withania somnifera) to prepupae of two economically important insect pests viz. S. litura and P. ricini resulted into disruption of molting and metamorphosis leading to a number of developmental aberrations such as prolongation of the life span of prepupae, postponement of pupal-adult ecdysis, ecdysial failure, reduced pupation and adult emergence, formation of larval-pupal and pupal-adult intermediates, abnormal pupae, and adultoids. Treatment with seed extracts of W. somnifera was more effective as it alone caused mortality in both the lepidopteran insects viz. S. litura and P. ricini, whereas no such effect was observed when treated with root extracts. P. ricini was more susceptible to W. somnifera as it resulted into formation of larval-pupal-adult chimeras in addition to effects described earlier, whereas this effect was not observed in the case of S. litura. Conclusion: These results are similar to these produced by the administration of JHAs and hence mimic their action by the way of interfering with the neuroendocrine system.

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