Cool temperatures and wet weather mean conditions are ripe for seedling blight. Watch out for these common diseases.
By Tamra Jackson-Ziems and Kevin Korus, University of Nebraska-Lincoln
Cool soil temperatures and episodes of rainfall are contributing to the development of seedling diseases in corn this spring. The most common seedling diseases that have been identified in samples submitted to the UNL Plant and Pest Diagnostic Clinic are those caused by Pythium and less frequently, Fusarium species.
Seedling diseases can be caused by any of several common soilborne organisms, such as Pythium, Fusarium, Rhizoctonia or plant parasitic nematodes. Seedling diseases are often difficult to diagnose because they have similar symptoms. Diagnosis of a specific disease may be of limited value because management may be similar for several seedling diseases. Microscopic examination and other laboratory analyses of the diseased seedlings often can identify the cause(s) of the problems.
Seedling diseases can be confused with insect injury, herbicide damage, planting problems, or environmental stresses that often have similar symptoms. Possible symptoms of seedling diseases include:
- Rotted seed prior to germination
- Rotted or discolored seedlings after germination prior to emergence
- Postemergence seedling damping off
- Root decay
At least 14 species of Pythium have been previously identified that can cause seedling blight and root rot. These pathogens require excessive moisture because they produce motile swimming zoospores that infect plant roots. The pathogen overwinters in soil and infected plant debris by producing thick-walled oospores that can survive for several years in the absence of a suitable host of favorable weather conditions.
Extension plant diagnostician Kevin Korus discusses findings of pythium in corn and soybean in this June 7 UNL Market Journal segment:
Although uncommon, Pythium also may cause stalk rot disease in corn during extended periods of wetness during the middle and later portions of the growing season. Symptoms of Pythium stalk rot can cause collapse of the lower stalks at or near the soil surface. Stalks may appear collapsed, twisted, and water-soaked and could be confused with bacterial stalk rot, except that they lack the characteristic foul odor.