natural-products-in-plant-pest-management

Allelochemicals in Pest Management 141term. The consumption in each experiment is measured using various digitizingleaf area meters.The bioassay is conducted for a very short duration (2 to 8 h) or until 50%of either disc is consumed. Several formulas and ways of denomination arepresented in the literature for calculating the biological effect (Koul, 2005).Nevertheless, the following formula to calculate feeding deterrence providesthe highest accuracy:Feeding deterrence (%) = (C – T)/(C + T) × 100, where C and T arethe consumption of control and treated discs, respectively (Koul, 2005;Pavela et al., 2008).As mentioned above, no-choice assays are most important from the practicalpoint of view, because they are closest in nature to practical application.It is thus advisable to favour such assays.When 90–100% feeding deterrence is obtained in the assays, efficientconcentration (EC 50and EC 95) can be determined in subsequent assays,which is another important parameter for the mutual comparison of extractor substance efficiency. Moreover, it is also of equal importance to determinethe time during which the given insect does not consume food treated withEC 95, as insects may become habituated to antifeedant substances or the biologicallyactive substances may be degraded due to the action of the environment(Koul, 2005). The insects can thus overcome the initial resistance againstfood treated with antifeedant substances, which may cause the products tolose their primary efficiency. However, it must be emphasized that in thisrespect, information on the period during which the insect does not consumefood treated with antifeedant substances is very sporadic, and therefore theexperiments must be completed with such information.6.5 Current Practical Use of Antifeedant SubstancesA long way still remains ahead in order to arrive at the full application potentialoffered by plant allomones in plant protection. No commercial productsbased purely on antifeedant efficiency are yet available. Nevertheless, someproducts that primarily contain substances with an insecticide effect, and atthe same time also show an antifeedant and anti-oviposition effect, are usedat present.Perhaps the most widely known application of antifeedant effects relatesto extracts made of the Indian plant Azadirachta indica A. Juss (syn. Melia azadirachta).A. indica has been well known in India and neighbouring countriesfor more than 2000 years as one of the most versatile medicinal plants havinga wide spectrum of biological activity. A. indica A. Juss and M. azedarach aretwo closely related species of Meliaceae.Extracts made of seeds of this plant contain numerous biologically activesubstances with insecticidal, fungicidal and bactericidal effects, used in manyindustries, ranging from medicine to agriculture. Many works have beenpublished concerning the plant itself, its useful substances, and biological