natural-products-in-plant-pest-management

142 R. Pavelaefficiency including antifeedant effects (Jacobson, 1989; Schmutterer, 1990;Ascher, 1993).In the case of A. indica, substances falling in the group of limonoids(azadirachtin, salanin, nimbin etc.) are responsible for antifeedant activity.Both primary and secondary antifeedant effects have been observed in thecase of azadirachtin (Ascher, 1993). Primary effects include the process ofchemoreception by the organism (e.g. sensory organs on mouthparts whichstimulate the organism to begin feeding), whereas secondary processesare effects such as gut motility disorders due to topical application only(Schmutterer, 1990; Ascher, 1993). Inhibition of feeding behaviour byazadirachtin results from the blockage of input receptors for phagostimulantsor by the stimulation of deterrent receptor cells or both (Mordue andBlackwell, 1993). In a recent study by Yoshida and Toscano (1994), the relativeconsumption rate of Heliothis virescens larvae treated with azadirachtinwas 25% of the control, equivalent to the lowest assimilation efficiency of allnatural insecticides tested. In another study, larvae of Heliothis virescens consumedless food, gained less weight, and were less efficient at convertingingested and digested food into biomass (Barnby and Klocke, 1987). Sensitivitybetween species to the antifeedant effects of azadirachtin is profound.Order Lepidoptera appear most sensitive to azadirachtin’s antifeedanteffects, with Coleoptera, Hemiptera and Homoptera being less sensitive(Mordue and Blackwell, 1993).A whole range of commercial products based on azadirachtin are sold atpresent; however, they utilize another significant effect of azadirachtin typetetranotriterpenoids, namely the growth inhibition effect (Schmutterer, 1990).Extracts from the Indian tree of the Pongamia genus are another exampleof the commercial application of products based on antifeedant andanti-oviposition effects. This genus has one species only, that is Pongamiapinnata L. (syn. P. glabra Vent.; Derris indica Lamk.) which belongs to familyLeguminosae; subfamily Papilionaceae (Kumar and Kalindhar, 2003).P. pinnata is a rich source of flavonoids, the B-ring is either linked to afuran or pyran ring. Some of these flavonoids are known to have biologicalactivity. Antifeedant activities of various extracts of P. pinnata were observedagainst many insect pests of different crops. Under laboratory conditions,0.1% water emulsion of pongam oil (so-called karanj oil) showed antifeedantactivity against Amsacta moorei Butler (Verma and Singh, 1985) or Spodopteralitura F. (Kumar and Kalindhar, 2003). The pongam oil is known to possessstrong repellent activity for egg-laying against many insect pests (Khaire et al.,1993; Kumar and Kalindhar, 2003). The aqueous extracts of seeds and plantsof this species are known to possess ovicidal action against Phthorimaeaoperculella Zell. and Helopeltis theivora Waterh. (Deka et al., 1998).The repellent activities, including host deterrence and anti- oviposition,of pongam oil against the adults of the common greenhouse whitefly Trialeurodesvaporariorum Westwood were tested in greenhouses (Pavela andHerda, 2007a,b). Chrysanthemum plants treated with different concentrations(0.5–2.0%) of water-suspended pongam oil showed relatively longlastinghost deterrent and anti-oviposition effects on the adults of greenhouse