Cause Several fungi or fungus-like microorganisms, mainly Pythium ultimum, Fusarium verticillioides, other Fusarium spp., and Penicillium oxalicum (on sweet corn). These microorganisms may overwinter on corn crop residue or in soil and are carried on seed. The diseases are more prevalent in poorly drained and excessively compacted or cold, wet soils. Planting poor quality seed increases seed rot and seedling blight as does planting seed too deep in wet, heavy soil.
Symptoms In cold soil, seeds decay or seedlings die before they emerge. In warmer soil, seedlings usually emerge but may show post-emergence dieback (damping-off) or are stunted and have brown, rotted roots and crowns.
Cultural control
- Select planting sites and dates to take advantage of warm soils.
- Plant high quality seed.
- Practice optimum water management, especially avoiding overwatering the first few weeks after planting.
- Crop rotation and destroying old corn stalks are helpful.
Chemical control Seed treatment with various fungicides.
- Acquire at 0.75 fl oz/100 lb seed plus a dye. For control of Pythium only. See label for reentry restrictions.
- Allegiance-FL at 0.75 fl oz/100 lb seed plus a dye. To control Pythium spp. See label for reentry restrictions.
- Apron XL at 0.32 to 0.64 fl oz/100 lb seed plus a dye for sweet corn if Pythium is a problem; for field or popcorn use at 0.0425 to 0.085 fl oz/100 lb seed. See label for reentry restrictions.
- Captan 4F at 2.2 fl oz/100 lb field corn seed or 4 fl oz/100 lb sweet corn seed plus a dye. For a broad spectrum of fungi.
- Dynasty at 0.153 fl oz/100 lb seed plus a dye. Use only in combination with labeled rates of Maxim and Apron XL. 4-hr reentry.
- Maxim 4FS at 0.08 to 0.16 fl oz/100 lb seed plus a dye for field corn and popcorn; at 0.08 fl oz/100 lb seed for sweet corn. For control of pathogenic Fusarium and Rhizoctonia spp. Requires additional Apron XL LS. See label for reentry restrictions Stamina at 0.38 to 0.76 fl oz/100 lb seed plus a dye.
- 42-S Thiram at 5 fl oz/100 lb sweet corn seed and 1.5 fl oz per bu of field corn seed plus a dye. For a broad spectrum of fungi. See label for reentry restrictions.
Biological control
- Actinovate AG at 3 to 12 oz/A as a soil drench at planting. 4-hr reentry. O
- Actinovate Lawn & Garden at 0.5 to 1 teaspoon/gal water. H O
- Bexfond at 7 to 14 fl oz/A. O
- Double Nickel LC at 0.5 to 4.5 pints/A as a soil drench at planting is labeled for sweet corn and popcorn. 4-hr reentry. O
- Heads Up at 0.035 oz/34 fl oz water/180 lb seed will stimulates pest suppression system of plants. Efficacy unknown. 12-hr reentry. O
- Mycostop at 0.07 oz/lb seed. 4-hr reentry. O