2011 Cercospora Resistance Maps

2011 Cercospora Maps

Comments Regarding Cercospora Sensitivity/Resistance Maps for 2011

  • Cercospora leafspot has developed much more extensive resistance to Eminent and Inspire.
  • Most serious Eminent and Inspire resistance concerns are from Moorhead to the Wahpeton area and from Crookston to East Grand Forks, see maps 2, 10, and 13.
  • While sensitivity/resistance was not specifically determined for Proline it is a triazole and cross resistance to specific modes of action to fungicides in the same class has been documented. Therefore it is recommended to use the same management strategies for all three triazoles.
  • Where + symbols appear they indicate that a sample at that location has resistance to the fungicide designated on that map.
  • If the + or + symbols are present in any given area for any specific fungicide then that fungicide should only be used with a suitable tank mix partner.
  • Resistance to Headline has been documented at 10 locations in the ACSC growing area.
  • Partial resistance has been documented at 39 locations in the ACSC growing area.
  • Always use a tank mix partner with Headline near any 2011 location with + or + symbol, map 7.
  • A total of 12 of 79 townships sampled (15%) have been identified that have resistance to tin fungicides, map 8. In these townships a mancozeb fungicide may be considered as a tank mix partner with Headline or triazole fungicides. Never use a mancozeb tank mix partner at less than full rates.
  • Resistance to Topsin remains at generally very low levels throughout the ACSC growing area, map 18. Topsin should be a very effective tank mix partner. Never use Topsin more than once per season in any field.
  • Never use Headline in a one spray program without a tank mix partner.
  • Never use triazoles without a tank mix partner in the ACSC growing area in 2012.
  • Contact your agriculturist for individual section locations for Cercospora resistance sample data.
  • Resistant strains of Cercospora beticola will be most effectively controlled using fungicide tank mixes at full rates of each product. Never use less than 75% of full rates of each product.
  • Contact your agriculturist for information regarding testing 2012 fields for the presence of strobilurin resistance before applying Headline in 2012.