c o

en the effect of pine chemistry on the natural enemies of pine herbivores. less volatile rosin fraction (mainly diterpene resin acids). Review TRENDS in Plant Science Vol.11 No.7 July 2006use chemical cues from the herbivore and host plant todeterring their oviposition or feeding, or against the physiology of the insects by reducing survival or fecundity [3]. In addition, volatile compounds can attract natural enemies of attacking herbivores, such as predators and parasitic wasps, thereby defending plants indirectly against attacking herbivores [4]. Predators and para-sitoids can have a significant impact on the population dynamics of forest insects [5]. Plants can influence predation and parasitism upon herbivores in many different ways [6]. Predatory and parasitic insects often The biosynthesis of terpenoids has been reviewed exten-sively and will not be covered here [11,12]. Biochemical and molecular aspects of conifer defences have attracted much attention in recent years. In particular, Norway spruce (Picea abies), Sitka spruce (Picea sitchensis) and grand fir (Abies grandis) have been used as model plants to study the molecular basis of constitutive and induced terpenoid-based defences; other members of the Pinaceae, such as loblolly pine (Pinus taeda) and Douglas fir (Pseudotsuga menziesii) have also been studied. Thedirected against the behaviour of herbivorous insects by upon herbivore attack. Defence mechanisms can be turpentine fraction (monoterpenes, sesquiterpenes) and aDirect and indirect of pine against foli