Agricultural Research Service plant physiologist Daniel Manter has found that extracts from tree heartwood can limit the growth of Phytophthora ramorum, the microbial agent that causes this devastating disease. Manter, with the ARS Soil Plant Nutrient Research Unit, Fort Collins, Colo., and his colleagues exposed spores to compounds, wood chips and essential oils extracted from heartwood. They found that extracts from incense cedar, western red cedar, Alaskan yellow cedar, western juniper and Port Orford cedar destroyed P. ramorum spores and inhibited fungal cell growth.

The western red cedar and incense cedar extracts damaged twice as many spores as the extracts taken from Alaskan yellow cedar, western juniper and Port Orford cedar. Douglas fir and redwood extracts showed little to no antimicrobial activity against the pathogen.