When to start spraying?

[Teamsterjohn]

Bud break started about 2 weeks ago on my Marquette vines. Now small leaves are starting to come out. When should I start spraying the vines to prevent powdery mildew from starting. Thanks John

 

[grapeman]

For effective management of powdery mildew, sprays may be required as early as 3- to 5-inch shoot growth on V. vinifera and highly susceptible hybrid cultivars, depending on rainfall and temperature in the early season. Note that cold nights near 40°F and below can significantly retard disease development, so spring seasons with overcast skies that minimize such episodes are at greater risk than those with a number of clear, cool nights.

 

[Teamsterjohn]

Thank you for the info