Abstract
The ability of the European spruce bark beetle, Ips typographus, to kill mature Norway spruce (Picea abies) trees in large outbreaks in northern Europe has stimulated much basic research on the interaction of these two species. Yet very little is known about what determines the fundamental outcome of bark beetle attack: How do beetles choose their hosts and why are certain trees more resistant than others? We apply new methodologies in molecular biology, insect electrophysiology, and analytical chemistry to these longstanding questions as part of a collaboration of 6 laboratories from Sweden, Norway, and Germany. In a natural stand of P. abies that is currently the focus of intense bark beetle attack samples are taken before attacks. We will first correlate the anatomical (traumatic resin ducts, phloem polyphenolic cells) and chemical defenses (terpene resin compounds and phenolics) of trees, their expression of defense genes, and the level of reserve carbohydrate with resistance to attack. Next, the volatile and surface chemistry of spruce bark will be assessed to determine which substances promote or deter attack. Compounds will be studied for electrophysiological responses in antennae and sensory cells, and in controlled behavioral experiments. Finally, to explore the potential of spruce defenses to protect standing trees, we will artificially induced defenses using treatment with methyl jasmonate and compare the survival of these trees to untreated controls.
Sweden