Site of aggregation pheromone biosynthesis in the pine engraver, Ips pini (Say), and the Jeffrey pine beetle, Dendroctonus jeffreyi

Bark beetles (Coleoptera: Scolytidae) are responsible for the loss of billions of cubic feet of standing coniferous timber annually and are considered the most destructive insectan forest pest in the Northern Hemisphere. Unfortunately, bark beetle infestations cannot be readily controlled by the traditional spraying of insecticides because beetles remain protected beneath the bark of host trees for the majority of their life cycles. Successful colonization of a host tree by pine bark beetles is dependent on a "mass attack" where hundreds to thousands of individuals are collectively able to overcome the defenses of the tree. The key element in the orchestration of this mass attack is the release of aggregation pheromone by pioneer individuals. Disruption of aggregation pheromone biosynthesis would provide a powerful means to specifically control the damage due to bark beetle populations.; Early studies suggested that bark beetles utilized host tree monoterpenes in the production of their aggregation pheromones. In the past decade, however, multiple lines of evidence concerning bark beetle pheromone production have emerged, bringing the host tree precursor modification model into serious question. Recently, the direct demonstration that unfed, juvenile hormone (JH) III-treated male I. pini and I. paraconfusus incorporated labeled acetate into ipsenol and ipsdienol has prompted the shift to a new model of de novo pheromone production via the mevalonate pathway. This discovery led to the re-emergence of a question that has lingered unanswered for over three decades: where are bark beetle pheromone components synthesized? This dissertation provides the first definitive demonstration that aggregation pheromone components are produced de novo in the anterior midgut tissue of two bark beetles, the pine engraver beetle, Ips pini (Say), and the Jeffrey pine beetle, Dendroctonus jeffreyi.