We’ve had some weird weather this year. April was cool and crop growth was delayed. But once May arrived, warm conditions lead to rapid development of fruit crops. We are now about “normal” in development. That means that grapes in the southern half of the state are nearing the pre-bloom stage, which is a key time to control important diseases such as black rot, downy mildew, and powdery mildew. The three or four sprays made from immediate pre-bloom to 4 weeks post bloom are critical for controlling fruit infections. Growers should pay extra attention to coverage, especially in the fruit zone, and use the best fungicides available. The Midwest Fruit Pest Management Guide lists recommended products. A protectant (FRAC M) such as Mancozeb, Captan or Ziram, plus one of the sterol inhibitors (FRAC 3) such as Mettle, Procure, Rally or Tebuzol is the recommended fungicide treatment. Rotating with a different mode of action, such the strobilurins (FRAC 11) Abound, Sovran, or Flint is a good option as well. The combination products such as Pristine, Inspire Super, Revus Top, Quadris Top and Adamant are also effective for broad-spectrum disease control. Be sure to read the warnings about phytotoxicity with fungicides containing difenoconazole. These next few sprays are critical to producing sound, clean fruit. Pay close attention to your sprayer output to be sure you’re getting thorough coverage. This is the most important time of the year for fruit disease control. Once we get 4 to 5 weeks past fruit set, disease pressure drops significantly.
Grape cluster at immediate pre-bloom stage
Grape cluster at early bloom