The largest fruit are 12 mm in diameter. The frosts on May 12 and 13 caused damage in many areas. This cool weather will halt moth flights and almost stop most insect development. After bloom growers can use insecticides to control leafroller larvae as well as cranberry fruit worm and cherry fruit worm . Grapes are almost in bloom.
Wild grapes are at full bloom.
Frost on May 12 and 13 damaged several hundred acres in SW Michigan causing damage to the canopy and flower clusters. In wine grapes, powdery mildew is also a concern. A final application of protectant fungicides should be made to protect the flowers and rachis from phomopsis, during a wet bloom. Grape berry moth adults are being trapped. Harvest on early varieties will probably begin late this week.