2007 Cercospora Resistance Maps

Comments for 2007 Cercospora Resistance Maps

Eminent resistance in 2006 compared to 2007

  • Virtually no use of Eminent in the Minn-Dak area in 2007 almost eliminated the presence of resistant samples.
  • Eminent resistant samples were virtually unchanged in ND in 2007 versus 2006.
  • Eminent resistant sample numbers increased from 2006 in the EGF, Crookston and Hillsboro districts in 2007 in Minnesota, but were still much lower than 2005.
  • Eminent resistant samples decreased in the Drayton and Moorhead districts in 2007, this was likely due to less spraying in Drayton and probably more tin use in Moorhead. Poorer yields in Clay county may also have resulted in more two spray programs with only tin and Headline use and less Eminent use.
  • Townships with partial resistance levels for Eminent are very prevalent throughout the RRV, NEVER use more than one triazole (Eminent, Proline, or Inspire SB) application per season.
  • ACSC recommendations for best disease control, greatest plant health benefits and ideal resistance management strategies for 2008 are to use a three spray program of a triazole followed by a tin followed by a Headline application.
  • If applying only two fungicide applications use tin followed by Headline or a triazole followed by Headline.
  • One spray programs should always be Headline.
  • All fungicide application timings should be based on a Headline application at the end of August or the first week of September.
  • No Cercospora control failures can yet be attributed to Eminent resistance.

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Headline Sensitivity/Resistance 2006-2007 Comparison

  • No samples had complete resistance to Headline in 2007, continued good news.
  • A total of 29 samples showed partial resistance to Headline in 2007 compared to 8 samples in 2006 and 34 in 2005.
  • Most partially resistant samples are in the Crookston, East Grand Forks and Drayton districts where many fields received only one fungicide application, usually Headline.
  • Very few samples in the Moorhead and Hillsboro districts had partial resistance.
  • Sections showing partial resistance in 2007 should receive two and preferably three applications of fungicide in 2008 to reduce possible partial resistance to Headline buildup.
  • Never use Headline more than once per season.

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Cercospora tolerance for TPTH in 2007

  • There is very, very little tin tolerance present anywhere in the RRV.
  • There have been slight increases in the number of samples showing slight tolerance compared to 2006.
  • Tin products should perform very well again in 2008.
  • ACSC recommends using tin as the second treatment in a three spray program in 2008.
  • Tin could be applied in mid-September if a 4th spray is required.
  • Always use the 5 oz/acre rate of tin.

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Cercospora Sensitivity/Resistance-2007 For Eminent/Headline

  • Twenty individual samples showed resistance to Eminent and partial resistance to Headline from the same sample compared to only 3 samples in 2006.
  • Fields in these sections should have a three spray program used in 2008, the spray program should be a triazole followed by tin followed by Headline.

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Please read and follow the ACSC Cercospora control recommendations for 2008 that will be posted on this site by May 1, 2008. These recommendations are based primarily on the research of Dr Larry Smith, UM-NWROC.