Effects of Recently Incorporated Organic Amendments on Damping-Off of Conifer Seedlings. R. E. Wall, Research Scientist, Maritimes Forest Research Centre, Canadian Forestry Service, Department of the Environment, P.O. Box 4000, Fredericton, N.B., Canada E3B 5P7. Plant Dis. 68:59-60. Accepted for publication 28 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-59.

In greenhouse tests, forest nursery soil containing the damping-off fungi Fusarium oxysporum, Rhizoctonia solani, and Pythium spp. was planted to oats (Avena sativa), rye (Secale cereale), buckwheat (Fagopyrum esculentum), and red clover (Trifolium pratense). After 15 and 20 wk, these green manure crops were incorporated into the soil, which was then amended with two levels each of sphagnum peat or fresh conifer sawdust. Black spruce and jack pine planted on these soils were not significantly affected by the peat or sawdust amendments but the oat, rye, and red clover green manure crops caused an increase in postemergence damping-off. Jack pine was most affected by 15-wk-old oats and rye. Black spruce had the most postemergence damping-off in soil containing 15-wk-old red clover. Based on these results and earlier studies, it is suggested that any green manure crop is potentially damaging if incorporated into soil immediately before planting.