Tests were conducted at the USDA Forest Service Nursery, Coeur d'Alene, Idaho to evaluate effectiveness of spring fumigation with dazomet to improve survival and performance of Douglas-fir and western white pine transplants. Spring fumigation greatly reduced populations of potentially pathogenic Fusarium and Pythium spp. Disease levels of container (plug+1) and bare root (2+1) Douglas-fir transplants were very low, regardless of soil fumigation. Fumigation reduced disease on bare root (2+1) white pine transplants, but did not improve survival of container (plug+1) white pine transplants. Seedling height growth during the first year after transplanting was significantly improved by soil fumigation. Fusarium oxysporum was commonly isolated from soil and roots of diseased bare root transplants. Fusarium proliferatum was commonly isolated from the roots of container transplants. Soil fumigation may not necessarily improve survival and performance of all types of conifer transplants in nurseries.
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