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Effect of Thiram on Germination of Douglas-fir Seed. W. J. Bloomberg, Forest Pathologist, Forest Research Laboratory, Canadian Forestry Service, Department of Fisheries and Forestry, Victoria, British Columbia; J. Trelawny, Technician, Forest Research Laboratory, Canadian Forestry Service, Department of Fisheries and Forestry, Victoria, British Columbia. Phytopathology 60:1111-1116. Accepted for publication 27 February 1970. DOI: 10.1094/Phyto-60-1111.

In low viability Douglas-fir seeds, treatment with 25% by wt thiram killed 12% of the seeds and delayed germination of the remainder. Germination of treated seeds was further delayed if seed coats were injured. An interaction between thiram treatment and stratification treatment affected germination percentage. In seeds with high viability, germination percentage was not affected, but germination was increasingly delayed by greater thiram dosage. Germination was further delayed if seeds were treated before stratification rather than after. Emergence percentage in nursery beds was lower than germination percentage; it was increased by 12.5 and 25% thiram treatment, but not by 50% treatment. Emergence failure was due equally to disease and inhibition of germination. Significant correlation occurred between emergence percentage and emergence speed. The correlations for treated and untreated seeds had the same slopes but differed in elevation. An interaction between seed density and thiram dosage affected emergence percentage in nursery beds.