See:
Corn (Zea mays) - Seed Rot, Damping-off, and Seedling Blight
Cause A fungal complex can incite root rot on dent and sweet corn. Fusarium spp. and Pythium spp. have been found on symptomatic plants from affected sweet corn fields in the Willamette Valley. Fusarium spp. and Pythium spp. are able to colonize other plant species, especially grassy species. These soilborne pathogens can also survive in affected plant residues, on asymptomatic hosts, as well as in soil.
A complex of these two fungi with a third fungus, Phoma sp., are found in corn grown in the eastern United States but this "Red Root Rot" disease has not been reported in commercial sweet corn fields in the Pacific Northwest.
Symptoms Root rot may develop as early as the 6-leaf stage on the primary or seminal roots and is noted by the present of rot or brownish lesions on the roots. Root rot may continue to develop and can be severe on the adventitious root portion, including rooted brace roots. Severe root rot may be apparent early season, at silking, or later.
Cultural control
- Plant tolerant varieties. Field corn appears to have greater root rot resistance than sweet corn. Sweet corn varietal screenings are underway in OSU and industry tests.
- Residue levels may enhance the population of pathogen so maximizing residue breakdown could be important in problem fields.
Chemical control Seed treatment with various fungicides can aid in controlling root rot of germlings but isn't thought to offer necessary protection against root rot later season.
- Apron XL LS at 0.32 to 0.64 fl oz/100 lb seed plus a dye for sweet corn if Pythium is a problem. See label for use on popcorn and field corn. See label for reentry restrictions.
- Allegiance-FL at 0.375 to 0.75 fl oz/100 lb seed plus a dye. Controls only Pythium spp. 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.
- Maxim XL at 0.167 to 0.334 fl oz/100 lb seed plus a dye, for sweet corn. See label for use on popcorn and field corn. For control of pathogenic Fusarium and Rhizoctonia spp. Requires additional Apron XL LS. See label for reentry restrictions.
- Tebuzol 3.6F at 0.071 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/bu field corn seed plus a dye. Controls a broad spectrum of fungi. See label for reentry restrictions.
Biological control
- Bexfond at 7 to 14 fl oz/A. O
- Mycostop at 0.07 oz/lb seed or Mycostop Mix at 0.05 to 0.08 oz/lb seed. 4-hr reentry. O