Recent cold, wet field conditions (in some cases snow) and fluctuations in soil temperatures have put early planted corn at risk for seedling disease development. Numerous seedling diseases can take advantage of any of these conditions. Be sure to monitor seedling emergence and stand establishment in the coming weeks so if problems occur they can be detected as early as possible.
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 their symptoms are very similar. Sometimes, diagnosis may be of limited value because management is often the same for several seedling diseases. Microscopic examination and other laboratory analyses of the diseased seedlings can often identify the cause(s) of the problems. Also, 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
- Post-emergence seedling damping off
- Root or hypocotyl decay
Unfortunately, hybrid resistance is not available for seedling diseases in corn. Where practical and in cases where flooding is a frequent concern, improved field drainage can help reduce the incidence and severity of some seedling diseases. Waiting to plant until soil conditions are warmer can promote rapid seed germination and emergence and help plants avoid infection and disease development. The most common method for disease management is the use of seed treatment fungicides.
Crop rotation can provide some reduction in disease, but some of the pathogens may also infect soybean and other crops.
Most seed corn is already treated with more than one seed treatment fungicide, often an insecticide, and, sometimes with a nematicide. These products can provide protection against some of the pathogens that cause seedling diseases; however, they only provide protection during the first few weeks immediately after planting. But, in spite of their activity, diseases may still develop, such as during extended periods of inclement weather or under severe pathogen pressure.
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