natural-products-in-plant-pest-management

14 N.K. Dubey et al.Dubey, 1999) (Fig. 9.1). The products showing chemosterilant activity arehighly required in integrated pest management programmes to limit thechances of physiological (resistant) race development by insects.Some of the essential oils have been found useful against those species ofpests that are resistant towards synthetic pesticides. These essential oils are acomplex mixture of components including minor constituents, in contrast tosynthetic pesticides based on single products, and they act synergisticallywithin the plant as a defence strategy. Hence, it is likely that they are moredurable towards pests evolving resistance (Feng and Isman, 1995). Due totheir largely environmentally friendly nature, they can be efficiently used forpest management in urban areas, homes and other sensitive areas such asschools, restaurants and hospitals (Isman, 2006).Octopamine (a biogenic amine found in insects) has a broad spectrum ofbiological roles in insects, acting as a neurotransmitter, neurohormone andcirculating neurohormone–neuromodulator (Evans, 1980; Hollingworth et al.,1984). Octopamine exerts its effects through interacting with at least twoclasses of receptors which, on the basis of pharmacological criteria, have beendesignated octopamine-1 and octopamine-2 (Evans, 1980). Interrupting thefunction of octopamine results in a total breakdown of the nervous system ininsects. Therefore, the octopaminergic system of insects represents a biorationaltarget for insect control. The lack of octopamine receptors in vertebratesprobably accounts for the profound selectivity of certain essential oilsas insecticides. A number of essential oil compounds have been demonstratedto act on the octopaminergic system of insects (Enan et al., 1998).Mode-of-action studies on monoterpenoids also indicate the inhibition ofacetylcholinesterase enzyme activity as the major site of action in insects(Rajendran and Sriranjini, 2008).Encapsulation is the suitable technology for the formulation of essentialoil-basedpesticides. The method reduces the loss of the active agents andoffers the possibility of a controlled release of oil vapours (Moretti et al., 1998).Essential oils can also be incorporated with polymers into sheets. Attractantadhesive films with essential oils have been prepared to control insects inagriculture and horticulture (Klerk’s Plastic Industries B.V., 1990).Many of the commercial products that include essential oils are on the‘Generally Recognised as Safe’ (GRAS) list fully approved by the Food andDrug Administration (FDA) and Environmental Protection Agency (EPA) inUSA for food and beverage consumption (Burt, 2004).OCH 3H 3 COOCH 3CH 3Fig. 1.9. β-Asarone.