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Reduce exposure to yield-robbing white mold.

Agronomy Bulletin 76 ─ White Mold

Situation

Caused by the fungus Sclerotinia sclerotiorum, soybean white mold has been problematic since the early 1990s, becoming more damaging in recent years.

Factors to Consider

  • Field history
  • Crop rotation
  • Tillage system
  • Seed varieties
  • Planting date
  • Plant spacing
Alter your approach in fields with white mold history to help recurring outbreaks.

Action Plan

  1. Weigh current management strategies against field history. Many current management practices used to increase soybean yields, including increasing plant density and canopy, also increase the risk of white mold development. If facing conditions favorable for white mold (wet and humid, with moderate temperatures), consider reducing plant canopy size and plant density —especially if the field has a history of white mold attacks.
  2. Consider rotating crops. Rotating to a nonhost crop for two years or more reduces risk. However, remember to control weeds when planting a nonhost crop, as many can serve as an alternative host for white mold.
  3. Understand how tillage impacts disease survival. Current research shows white mold can survive many years when buried in the soil. Therefore, conventional tillage actually aids in the survival of white mold, bringing buried sclerotia to the surface, where it can infect plants. Conversely, a no-till system minimizes disease outbreak.
  4. Select varities to combat white mold. In high-risk fields, choose a variety with high tolerance — especially important if planting in narrow rows or at a high population. Also, consider selecting a short-stature variety that will not increase the plant canopy.
  5. Determine planting date. While planting early increases the yield potential of soybeans because of the longer growing season, it also heightens the risk for white mold potential by increasing plant canopy. Fields with a history of severe white mold should be planted later in the season.
  6. Plant for lower populations with wider spacing. Management strategies that increase plant growth speed and canopy closure simultaneously increase the risk of white mold. Increasing row width can diffuse this problem in fields with a severe white mold history. If planting at a lower population, consider a seed treatment to maintain ideal plant populations.

Summary

White mold can be devastating to soybean yields, but a prepared grower can confidently navigate the risk factors. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Published on Friday, August 23, 2013