Fungicide management of maize head smut (Sphacelotheca reiliana) by seed treatment.
Two pot experiments were conducted at the Lumle Agricultural Research Centre, Nepal in 1991 and 1992 to evaluate the effectiveness of maize seed treatment with triadimenol (Baytan), Sumi-8 (diniconazole) and tebuconazole (Raxil-50) for prevention of head smut (S. reiliana). The fungicides effectively controlled the disease in both years, with plants from treated seeds developing <3% smut. These fungicides were then tested under conditions of artificial exposure at 3 mid-hill sites in farmers' fields in the 1994 season (with propiconazole (Tilt-250) replacing Sumi-8). Propiconazole, tebuconazole and triadimenol were applied at the rate of 4 ml or 4 g kg-1 of maize seeds. The lowest percentage of S. reiliana-infected plants was produced by treatment with propiconazole (0.7%), followed by tebuconazole (6.1%) and triadimenol (13.2%) (compared with 35.9% infection in untreated control plants). Seed treatment with propiconazole produced a stunting effect at the seedling stage from which the plants recovered later in the growth phase. However, treatment with a lower rate of propiconazole (2-3 ml kg-1 seed) had less detrimental effects on seedling growth.