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Be aware of common diseases after a wet spring

Scout fields for any issues


Weather in 2019 is showing to be one of the wettest seasons on record. Cooler temperatures have slowed soil drying, which may have caused some diseases to occur as a result of slow germination and early season growth. It is important for farmers to be scouting their fields early on to determine if their crop is off to a healthy start. 

For farmers who were able to get some corn planted before the season turned wet, it may be hard to distinguish if emergence issues are a result of environmental stress or if a seedling disease is also developing. If it is environmental, the plants should start to recover as soils get warmer and more drained.

Diseases to know
Pythium, Fusarium and Rhizoctonia are the main concern for early wet conditions. Add in the impact of environmental stress and seedlings are under greater risk for damage. Because it’s difficult to identify the fungi, send it to a diagnostic lab to be able to isolate specific or multiple species. You may be tempted to ignore the disease identification, but knowing which disease is present may help you make hybrid or seed treatment decisions in the future.

Check plant stand
Look at plant color and size. Newly emerged plants should be consistent in color and growth stage. When pulled out of the ground, the plant should have a white, healthy root system. A dark-colored root indicates the plant might be under cold stress or infected with fungi, such as Fusarium, Penicillium, Pythium or Rhizoctonia

To achieve maximum yield potential, all plants in the field need to have emerged within 24 to 48 hours of each other. If some plants are behind others in growth, dig up a few and compare them with healthy plants. Look for areas of rotted roots, brown lesions on the mesocotyl region and other injury to the roots, such as compaction. Compare the color of the plants. A more yellowish color of one plant versus another may indicate fertilizer burn or another issue with plant growth.

Scout regularly
Review your fields to identify areas that have been impacted by disease. Easy identifiers include skips within a row or pockets of stunted or disclolored plants. This is a sign of areas that retained water and did not drain effectively. Dig up plants that did not emerge to see if the lack of germination was related to a skip in the planter or was the plants leafing out underground. 

Some plants may not die from the disease early in the season, though issues may surface later in the season. Plants infected with a disease such as Fusarium may be stunted compared with other plants, and it’s possible crown rots could emerge under the right conditions.

Foliar applications are not able to correct the impact of seedling diseases. Consult with your agronomist and ag retailer to build a solid plan to help navigate through this challenging season.

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Published on Wednesday, June 05, 2019 by Andy Robinson, Mycogen commercial agronomist