Powdery mildew control
I have been controlling powdery mildew on my apple trees by spraying. My question is: since spraying happens before mildew is evident, does it come back every year? If I don't spray will it occur again? My trees are several years old. The mildew greatly stunted them before I figured out what it was.
Jackson County Oregon
Thank you for your question. Powdery mildew is a fungus and, although you can prevent it one year, that prevention does not extend to the next year. If you don't spray at the correct time--before the blossoms open--it will recur each year. But timing is important. Here is an article with information on what to use each year (probably too late for 2019): https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec631_0.pdf
Hope this is helpful. Good luck!