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Root Rots, Seedling Blights, and Seed Decay of Corn (05/30/19)

Corn seed that has been in the soil for a couple weeks without emerging may be impacted by soil-borne and/or residue-borne pathogens.

Corn seed that has been in the soil for a couple weeks without emerging may be impacted by soil-borne and/or residue-borne pathogens. Although the saturated soils can cause abiotic disorders in plants, the conditions can increase the risk for root rot, seedling blight and seed decay issues. The two most common pathogens associated with these corn diseases in North Dakota are Pythium and Fusarium. Pythium-associated problems are favored by cold, wet soils and will be more problematic in the wettest areas of a field (low spots). Fusarium has a wider range of favorable temperatures and moisture conditions and is common in corn plants that have been stressed by cold temperatures, compactions, and saturated soils.

Distinguishing between the two pathogens based on plant symptoms is very difficult and laboratory methods are often needed. To determine if a pathogen is causing stunting or wilting, dig up the entire corn plant (don’t pull on above ground tissue) and check to see if the mesocotyl region is discolored or if the seed is rotted (Figure 1).

ppth.1

Fungicide Seed Treatments

Seed treatment fungicides containing metalaxyl, mefenoxam or ethaboxam will have the best activity on Pythium. For Fusarium­, several fungicide groups have activity including demethylation inhibitors (DMIs/FRAC 3), Quinone outside inhibitors (Strobilurins/FRAC 11) and Succinate dehydrogenase inhibitors (SDHIs/FRAC 7). The effective residual from any of these fungicides is around two to three weeks (depending on soil conditions).

For more information on seed decay, seedling blights and root rots of corn please use the North Dakota Plant Disease Management Guide (HYPERLINK) and the Crop Protection Network website.

 

Andrew Friskop

Extension Plant Pathology, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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