Extended Abstract on the Potential for Phytophthora ramorum to Infest Finished Compost

The survival rate of Phytophthora ramorum was assessed when introduced at high rates into composts of varying provenance and curing time, produced by both “turned windrow” and “forced air static pile” techniques. Survival in some compost media was high and statistically indistinguishable from positive controls (P<0.01), while other sources were statistically indistinguishable from negative controls (P<0.01). The difference between positive and negative controls was large and highly significant (P<0.01). We found no significant differences in survival rates between compost processing techniques or curing time. No compost material was so suppressive of P. ramorum that it could not be re-infested after the composting process was finished. This suggests that measures should be taken to insure that finished compost is not contaminated by infested greenwaste.