OXYGEN DEFICIENCY AND SPRUCE RESIN INHIBITION OF GROWTH OF BLUE STAIN FUNGI ASSOCIATED WITH IPS-TYPOGRAPHUS

The Eurasian spruce bark beetle, Ips typographus, carries spores of several fungi including Ophiostoma bicolor, O. penicillatum and O. polonicum. However, after attack on Norway spruce trees O. polonicum is the pioneer invader of the sapwood while other species follow. To determine the causes behind this distinct succession experiments were performed comparing growth rate, tolerance to oxygen-deficient conditions and to spruce resin between these early invaders. In sealed tubes with limited oxygen, O. polonicum grew for a longer time than three other species regularly associated with I. typographus in Norway. The non-volatile components of lesion resin induced by fungal attack, as opposed to preformed resin, inhibited the growth of all species, but particularly O. polonicum. O. polonicum grew rapidly on malt agar, but not faster than some of the other species associated with I. typographus. It is concluded that rapid growth and the ability to tolerate low oxygen pressure are important attributes for primary invaders, allowing tree resistance mechanisms to be overcome following mass inoculation.