 Powdery mildew: Powdery mildew can be a persistent disease of
susceptible apple cultivars throughout the mid-Atlantic region. It is the only fungal
apple disease that is capable of infecting without wetting from rain or dew. Mildew
severity and the need for control measures are related to cultivar susceptibility and
intended fruit market.Management: The management of powdery mildew in commercial orchards must be integrated with several other diseases having different environmental requirements (i.e. apple scab and cedar-apple rust). Where mildew-susceptible cultivars are grown, include a mildewcide in the scab program to control both diseases. The DMI fungicides are effective against both diseases, as well as the rust diseases. Begin sprays at tight cluster and continue until terminal growth stops. Early season sprays (tight cluster to petal fall) are essential if mildew is to be managed successfully. The interval between sprays is generally 7 days during the stages of rapid leaf development before petal fall and 12 - 14 days during the post bloom period. During the early season, fungicide applications at lower rates on a 7-day schedule are more effective for controlling mildew than higher rates applied on a 10-day schedule. |