Tuesday, August 20, 2013

Disease risks 8/14, 17, and 20

Continuous rain and high relative humidity caused Botrytis and downy mildew infection risk events on the 14th, 17th, and 20th.

At this point of the season, a phosphite (aka phosphonate or phosphorous acid) material would be the best choice for downy mildew.  You may want to mix it will captan to have added efficacy. (Note: captan has 0-day PHI, but some winemaker prefer not having captan close (~3 weeks) to the harvest.)  The other potential mixing partner would be Ranman (note PHI = 30 days), Forum (PHI=28 days), or Revus (PHI=14 days).  Ranman should have some kick-back activity, and both Forum and Revus have a protective activity.

As for Botrytis, we only have protective action materials, thus, please make sure to have a good coverage on your clusters.  Moreover, please make sure to rotate mode of action since this pathogen is known to develop resistance to fungicide rapidly.

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