Cause Several fungi or fungus-like microorganisms, mainly Globisporangium ultimum (formerly Pythium ultimum), Fusarium verticillioides, other Fusarium spp., and Penicillium oxalicum (on sweet corn). Recently the genus Pythium Pringsheim (nom. cons.) sensu lato (s.l.) was reorganized into three genera based on DNA sequencing and molecular phylogenetics: Pythium, Elongisporangium, and Globisporangium by Nguyen et al. (2022). The Pythium-like microbes that may be present in grower fields could fall into the genus Globisporangium or Pythium species. Seed rot, damping-off, and seedling diseases of corn caused by Pythium aphanidermatum and P. graminicola have been reported on corn on the west coast (California), but likely Globisporangium irregulare (formerly P. irregular), P. sylvaticum in addition to G. ultimum incite disease in the Pacific Northwest; overall 44 Pythium/Globisporangium species have been implicated in seed and seedling blight of corn in the US.
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 (Group 4) at 0.75 fl oz/100 lb seed plus a dye. For control of Pythium and Globisporangium spp. See label for reentry restrictions.
- Allegiance-FL (Group 4) at 0.75 fl oz/100 lb seed plus a dye. To control Pythium and Globisporangium spp. See label for reentry restrictions.
- Apron XL (Group 4) at 0.32 to 0.64 fl oz/100 lb seed plus a dye for sweet corn if Pythium and Globisporangium are 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 (Group M4) 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 (Group 11) 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.
- Intego Solo Fungicide Seed Treatment (Group 22) at 0.2 to 0.3 fl oz/100 lb of seeds if Pythium and Globisporangium are a problem. 12-hr reentry.
- Maxim 4FS (Group 12) 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. See label for reentry restrictions Stamina at 0.38 to 0.76 fl oz/100 lb seed plus a dye.
- 42-S Thiram (Group M3) 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
- Bexfond at 7 to 14 fl oz/A. 4-hr reentry. O
- Double Nickel LC is labeled for sweet corn and popcorn at 1 to 2 quarts/A as a banded soil spray or drench on 4- to 6-week intervals or at 0.5 to 4.5 pints/A on 2- to 4-week intervals. 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
- LALSTOP K61 as a seed soak or dry seed treatment, soil-spray or drench, etc. See label for rates and application methods. 4-hr reentry. O
References Bickel, J.T., and Koehler, A.M. 2021. Review of Pythium species causing damping-off in corn. Plant Health Progress 22: 219-225. https://doi.org/10.1094/PHP-02-21-0046-FI.
Broders, K.D., Lipps, P.E., Paul, P.A., and Dorrance, A.E. 2007. Characterization of Pythium spp. associated with corn and soybean seed and seedling disease in Ohio. Plant Dis. 91:727-735.
Nguyen, H.D.T., Dodge, A., Dadej, K., Rintoul, T.L., Ponomareva, E., Martin, F.N., de Cock, A.W.M., Lévesque, C.A., Redhead, S.A., and Spies, C.F.J. 2022. Whole genome sequencing and phylogenomic analysis show support for the splitting of genus Pythium. Mycologia 114(3):501-515. https://doi.org/10.1080/00275514.2022.2045116.
Radmer, L., Anderson, G., Malvick, D.M., Kurle, J.E., Rendahl, A. and Mallik, A. 2017. Pythium, Phytophthora, and Phytopythium spp. associated with soybean in Minnesota, their relative aggressiveness on soybean and corn, and their sensitivity to seed treatment fungicides. Plant Dis. 101:62-72.
Rojas, J.A., Chilvers, M.I., Jacobs, J.L., Noel, Z.A., and Witte, A. 2019. Diversity and characterization of oomycetes associated with corn seedlings in Michigan. Phytobiomes J. 3(3):224-234.