This report summarizes the second year of a two year study on Douglas-fir dieback. Dieback of container-grown Douglas-fir seedlings is caused by a minor root pathogen, Pythium. Possible sources of Pythium in nursery mixes include peat, water, air-borne spores and reuse of contaminated styroblocks. The incidence and severity of dieback damage are strongly influenced (1) by seedling susceptibility to the pathogen, which is highest the first few weeks after germination, and (2) by the environmental conditions, particularly the moisture content, temperature and pH of the growing mix.
FRDA Research Report 142 (2603 KB)
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Updated July 24, 2015