As a consequence, many aphids do not survive during migration because of starvation or ground predators [18]. Moreover, EβF may substantially enhance the effectiveness of pesticides

and mycoinsecticides by increasing aphid mobility [19] and [20]. EβF can also function as a kairomone (a chemical messenger emitted by organisms of one species but benefitting members of another species) in attracting aphid predators, including ladybirds [21] and [22], lacewings [21], hoverfly [23] and parasitoids [24], and thus recruit natural enemies for aphid control. EβF occurs in the essential oils of plant species such as chamomile [25], Garland [26], Hemizygia petiolata [27], water pepper [28], and black peppermint Ribociclib chemical structure NVP-BKM120 clinical trial [17]. In field plot experiments, the numbers of pea aphid (A. pisum) were significantly reduced when sprayed with essential oil from H. petiolata, an oil that is rich in EβF (more than 70% EβF) [27]. EβF is also a component of some plant volatiles. In natural environments, wild potato, Solanum berthaultii, releases high quantities of endogenous sesquiterpene EβF from specialized foliar trichomes, that are more repellent to the green peach aphid than the oil in commercial potato varieties which

produce lower levels of EβF along with some inhibitory compounds such as (E)-caryophyllene [29], [30] and [31]. EβF emission can be induced by herbivory in certain plants [32] and [33], and insect-induced EβF has been hypothesized to function either as a direct repellent to insects (i.e., alarm pheromone function) PRKACG or act as a kairomone for natural enemies of aphids [34]. For example, caterpillar-damaged maize releasing EβF repels the corn

leaf aphid Rhopalosiphum maidis [35], and oviposition-induced EβF from pine was shown to attract the parasitoid Chrysonotomyia ruforum [33] and [36]. The potential importance of EβF for aphid control in plants has prompted the cloning of genes related to its synthesis. EβF synthase genes that encode an enzyme converting farnesyl diphosphate (FPP) to EβF have been isolated and characterized in several plant species, including Douglas fir, Yuzu, sweet wormwood and black peppermint [37]. In vitro analysis showed that EβF synthase from peppermint (Mentha × piperita L.) could convert FPP to EβF [17]. Expression of the EβF synthase gene from black peppermint in Arabidopsis repelled aphids and attracted aphid parasitoids at a significant level [38]. Moreover, EβF-emitting transgenic Arabidopsis allowed aphids to habituate to their own alarm pheromone; habituated aphids then showed no avoidance response to EβF, thereby increasing predator and parasitoid efficiency [34]. Overexpression of sweet wormwood EβF synthase genes in tobacco also resulted in reduced aphid infestation [39]. These results indicated that genetic engineering of plants to produce EβF for aphid control could be feasible.