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Protect BMR corn silage with foliar fungicides.

Agronomy Bulletin 70 ─ Silage Disease Control

Virtually all tasseled hybrids are threatened by foliar diseases, with risk varying in each field.

Situation

If foliar diseases threaten brown midrib corn (BMR) silage fields, growers can mitigate risks under the right circumstances with proactive management. Are you familiar with best practices for protecting your silage crop?

Factors to Consider

  • Disease susceptibility level
  • Disease identification and assessment
  • Field history
  • Fungicides
  • Weather
  • Label restrictions

Action Plan

  1. Understand susceptibility of different hybrids. Generally, hybrids that are more susceptible to fungal diseases will have a greater response to a foliar fungicide. To learn more information about the plant’s susceptibility to common leaf diseases, select a hybrid and then click on the “Management Guidelines” tab.
  2. Maintain thorough records of field history. Avoid planting in areas with high disease pressure, in fields with low areas or those bordered by trees. Because many foliar pathogens survive in corn residue on the soil surface, the risk of disease increases when corn is planted into the same field for consecutive years.
  3. Account for weather. Rain and humidity create an environment for foliar disease development. Diseases tend to spread and become more severe with continued clouds and extended dew periods of at least 12 hours. Conversely, hot and dry conditions can suppress disease growth.
  4. Observe indicators. Proper recognition of fungal disease is critical. Gray leaf spot, which can reduce yield by 40 percent, produces tan lesions with a grayish cast. Northern corn leaf blight can be identified by grayish-green cylinders that reach up to 15 centimeters in length. Eyespot symptoms are dark brown, circular lesions with a diameter of one-eighth of an inch.
  5. Scout fields prior to tasseling. This is crucial in determining the level of disease prior to fungicide application. To calculate disease incidence, count the number of plants with a specific disease present as a percentage of the total number of plants assessed. The difficulty is predicting the level of disease-related damage at harvest. This depends on weather, an unknown variable, between fungicide application and harvest.
  6. Determine use of fungicides. Fungicides will control only fungal diseases, not bacterial diseases. If at least 50 percent of susceptible hybrids are showing fungal disease symptoms, consider applying a fungicide. Treatment also may be effective if an intermediate hybrid field has 50 percent symptoms, surface residue is at least 35 percent and environmental conditions have been favorable for disease. Fungicides generally are not recommended for resistant hybrids.
  7. As always, follow label directions. Apply fungicide at the correct rate for the corn plant’s growth stage and adhere to any restrictions on spray quantities and harvest dates.

Summary

Foliar diseases can be costly. Minimize your risk with smart management, considering weather conditions and field history and applying fungicides if needed. Fungicide treatments on BMR silage are most effective when disease pressure is moderate to severe. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Published on Monday, August 05, 2013