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Powdery Mildew: Mid-Season Public Enemy #1

May 12, 2022
powdery mildew on grapes

Grapes infected with powdery mildew

As the grape production calendar turns to mid-season, so does the increased threat of powdery mildew. A perennial and common disease for all varieties of wine, raisin and table grapes, producers should have a plan to battle potential quality and yield losses all summer long.

Spring 2022 has been relatively dry, and it is possible some grape producers put off sprays at bud break while banking on a lower likelihood of powdery mildew. However, there may still be a decent amount of inoculum ready to spread since the spores overwinter in vines. As temperatures warm, powdery mildew could increasingly become a problem without timely sprays.

Powdery mildew also favors high humidity. The leafy canopies that form in the vineyards can serve as microclimates for humidity and spur on disease development. Powdery mildew attacks not only leaves, but also grape clusters and cluster structures, putting yield and quality at risk.

Fortunately, producers have several, effective methods for all-season powdery mildew control that can delay the onset of resistance to key active ingredients. Rotating modes of action during the season helps manage repeated infections when treated at appropriate intervals. Here are some of the options producers may consider to maximize mid-season resistance management plans:

  • Apply sulfur at bud break to enhance overall fungicide efficacy. Rotate with conventional chemistry and with other products listed below that have varied strengths as noted.
  • Inspire Super® fungicide, which contains difenoconazole and cyprodinil, is a solid choice for resistance management that offers both early- and late-season powdery mildew control. Inspire Super is a strong partner for mode of action rotations and has activity on Botrytis.
  • Aprovia® Top fungicide also contains difenoconazole, along with benzovindiflupyr, a Group 3, 7 with long-lasting residual control. A newer product for grape growers, Aprovia Top is a powdery mildew specialist that is effective when used between sulfur and conventional chemistries. It also is one of the best fungicides on the market for the disease.
  • Miravis® Prime fungicide is the flagship product for powdery mildew control. The Adepidyn™ technology and fludioxonil fungicide is a powerful Group 12, 7 fungicide, so it is an ideal resistance management tool for a fully-charged defense against difficult diseases. Miravis Prime provides both powdery mildew and Botrytis control with a residual that is 10-15% longer than conventional chemistries. Miravis Prime can be the anchor for any powdery mildew management program.

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