Effects of Thiram on Douglas-Fir Seedlings

Douglas-fir seedlings were sprayed with Thiram (tetra methyl thiuram disulfide) to test its fungicidal and therapeutic action against Botrytis sp. The study was made after an unexpected frost injured many 1-year-old seedlings in the Oregon Forest Nursery, north of Corvallis, in November 1959. Within a short time, infection of the damaged plants by Botrytis became general, as shown by isolations at the laboratory. Part of a regular nursery bed 48 inches wide was divided into nineteen 3-foot plots with 3-foot buffer blocks between plots. Aqueous solutions of Thiram were applied in two concentrations, 0.3 and 0.6 percent. The plots were sprayed in 1960 one to eight times with two concentrations (fig. 1). One plot was sprayed on April 8, and an additional plot was sprayed on April 22, May 6, May 20, June 3, June 17, July 8, and July 22. Thus, eight plots were sprayed on July 22.

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Author(s): Max Halber

Publication: Tree Planters' Notes - Issue 61 (1963)