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568 - Cercospora Management: New Challenges – New Changes

SUCCESSFUL CERCOSPORA MANAGEMENT HAS TO MEET SEVERAL OBJECTIVES FOR 2012. MOST IMPORTANTLY CERCOSPORA MUST BE KEPT under control to maximize crop yield, quality, and profitability. Another critical objective is preventing Cercospora resistance buildup to registered fungicides or where resistance is already present reducing or eliminating presence of these resistant isolates. Sugarbeet growers in Michigan experienced failure of Headline to adequately control Cercospora in 2011, see Figure 1.

Figure 1. Cercospora Fungicide Trial - Elkton, 2011

North Dakota State University and USDA Plant Pathologists have been testing Cercospora isolates from RRV fields for many years. Limited resistance to the Strobilurin fungicide Headline has been documented. More widespread resistance has developed to the Triazole fungicides, Eminent, Proline and Inspire. Resistance to one Triazole fungicide in a field usually means there is cross resistance to other Triazoles as well. To identify mapped locations with resistance to fungicides go to, then to Agronomy, then to Ag Tools, then to Pest Alert then under Cercospora Resistance Maps click on 2011. For more detailed locations of resistance development in past years your agriculturist has section by section maps of the entire RRV.

NDSU/UM Cercospora Trials, 2011, Dr. Khan

Strategies to Manage Fungicide Resistance

  • Carefully monitor weather conditions
  • Initiate spray programs when Cercospora is initially discovered in your piling district/county
  • Use adequate spray volumes and pressures
  • Rotate classes of fungicides
  • Use tank mixes of fungicides - See Figure 2
  • Use high rates of fungicides
  • Maintain proper application intervals

Fungicide Classes

Recommended Spray Programs

Other Important Considerations:

  • Triazole fungicides should not be used alone in the RRV - See Figure 2
  • Eminent should not be used in the Moorhead factory district
  • Topsin should never be used more than once per season
  • EBDC tank mixes should only be used once per season
  • Headline is very important for plant health and frost protection apply it late August or early September
  • Triazoles/Headline/Topsin and EBDC Products should be used at full rates in tank mixes
  • Tin fungicides can be used at ¾ of full rates in tank mixes
  • Proline may give slight additional Rhizoctonia control
  • Early prepile harvest necessitates careful management of preharvest intervals
  • Contact your agriculturist regarding fungicide compatibility and concerns with crop phytotoxicity with glyphosate tank mixes
  • EBDC tank mixes require good tank agitation

Fungicide Use Specifications