SYSTEMIC EFFECTS OF HETEROBASIDION ANNOSUM ON THE SECONDARY METABOLISM OF PONDEROSA PINE AND THEIR POTENTIAL CONSEQUENCES FOR BARK BEETLE BEHAVIOUR
P BONELLO1, TR GORDON1, AJ STORER2, WR MCNEE2 and DL WOOD2
1Department of Plant Pathology, Hutchison Hall, University of California, Davis, CA 95616, USA; 2Department of ESPM, Wellman Hall, University of California, Berkeley, CA 94720, USA
Background and objectives
In particular, we present data addressing the possibility that (i) pathogen-induced, elevated evolution of ethylene from the canopy may be a mechanism of primary attraction of bark beetles; and (ii) root infection may induce systemic accumulation of auto-toxic soluble phenolic compounds of host origin which may affect beetle feeding behaviour.
Results and conclusions
In two independent greenhouse studies, it was found that systemic accumulation of the pine stilbenes pinosylvin and pinosylvin monomethylether was associated with symptom expression in artificially inoculated 4-year-old ponderosa pine trees. This confirms results from a previous study in which autotoxicity of pine stilbenes was demonstrated in 6-week-old Scots pine seedlings , and indicates that stilbene autotoxicity may be one of the steps that, directly or indirectly, render infected trees palatable to bark beetles.
Although these results are preliminary, certain phenomena are beginning to appear that may shed light on the complex physiological mechanisms underlying the relationships between root disease agents, hosts, and tree killing bark beetles. It is expected that a better understanding of these interactions will enable more directed efforts to identify control measures which will maintain forest productivity in the future.