Fungicide Seed Treatments Influence Emergence of Winter Wheat in Cold Soil

Abstract

Winter wheat (Triticum aestivum L.) in the Pacific Northwest (PNW) is typically planted when soils are warm (75°F) to cool (50°F). Drought during 1994 delayed planting in some fields until soils were cold (35-45°F). Emergence in cold, wet soil was slow and often incomplete and, in some circumstances, appeared to differ for seed treated with different fungicides. Experiments were performed in the field and greenhouse to provide improved treatment guidelines for winter wheat planted into cold soil. Emphasis was on the fungicides Vitavax (carboxin [2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin]), Dividend 3FS (difenoconazole [1-(2-[4-(4-chlorophenoxy)-2-chlorophenyl]-4-methyl-1,3-dioxolan-2-yl-methyl)-1H-1,2,4-triazole]), Thiram (tetramethylthiuram disulfide) and Apron (metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-alanine methyl ester]). Emergence of winter wheat from cold (38°F) soil was more complete when seed was treated with mixtures of Dividend + Apron, Dividend + Thiram, or RTU Vitavax Thiram than with Dividend alone or untreated. Differences in emergence were caused by Pythium root rot. Treatments including Thiram, Apron, or another fungicide toxic to Pythium species are recommended for winter wheat seed planted after about 15 October in the PNW.