natural-products-in-plant-pest-management

10 N.K. Dubey et al.Carvonelacking in the other plant parts (roots, bulbs, stems and leaves). It is interestingthat the toxic constituents actually become more powerful after storage.Sabadilla is considered among the least toxic of botanical insecticides,with an oral LD 50of 4000–5000 mg/kg (in mice) (Dayan et al., 2009). It slowsdown the shutting of Na + channels and disturbs membrane depolarization,causing paralysis before death (Bloomquist, 1996). No residue is left after theapplication of sabadilla because it breaks down rapidly in sunlight.Carvone is a monoterpene of the essential oil of Carum carvi (see Fig. 1.5 forthe structure). It is a non-toxic botanical pesticide under the trade nameTALENT. It inhibits the sprouting of potato tubers during storage and protectsthem from bacterial rotting without exhibiting mammalian toxicity.Thus, it enhances the shelf life of stored fruits and vegetables and inhibitsmicrobial deterioration without altering the taste and odour of the fruits aftertreatment (Varma and Dubey, 1999). The LD 50value of carvone (in mice) isreported to be 1640 mg/kg (Isman, 2006).Allyl isothiocyanateAllyl isothiocyanate (Fig. 1.6) is an organosulfur compound that serves theplant as a defence against herbivores. Because it is harmful to the plant itself,it is stored in the harmless form of the glucosinolate, separate from themyrosinase enzyme present in plants. When an animal chews the plant, theallyl isothiocyanate is released due to action of myrosinase enzyme, thusrepelling the animal.Members of the plant family Brassicaceae are chemically linked by thealmost universal presence of glucosinolates, a class of sulfur-containingglycosides, also called mustard oil glycosides or thioglucosides. Thesecompounds are considered the first line of defence of crucifers against insectsand other organisms (Renwick, 1996).OH 3 CCCH 2CH 3Fig. 1.5. Carvone.NCSFig. 1.6. Allyl isothiocyanate.