Disease of Douglas-Fir Seeds During Cone Storage

Seeds in Douglas-fir cones stored for 225 days under operational conditions were free of disease; but during germination tests after extraction, up to 56 percent of them became diseased. Almost all nongerminable seeds were diseased. Disease incidence increased to different extents with length of cone storage in 3 cone lots and fluctuated in another. Bacteria and several fungi were associated with the disease. Storing extracted seeds at 40° F for 7 months did not affect the disease incidence. Also unrelated to disease incidence were cone moisture content, scale opening, pitchiness, percentage of cone surface covered by mycelia, density of mycelia around seeds in cones, fungus genera, and number of empty seeds. The results suggest that disease incidence is a function of cone-storage period and the disease resistance, which is expressed only under conditions of the germination tests, and is positively correlated with seed maturity.