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Powdery Mildew

Posted by Nathaniel Bouman 
Powdery Mildew
November 13, 2017 11:30AM
I've got a bad powdery mildew problem in my apple orchard. The stokes red are particularly bad off (the whole orchard is 3 years old) and it's affecting the growth of the trees. Most of the smaller branches are sheathed in white on the stokes red. It's a problem that really took off during the drought of 2016 (no rain but it stayed humid enough here). I was too inexperienced to catch it then and then this past season my attempts at control were kind of haphazard. I tried:
potassium bicarbonate
sodium bicarbonate
stylet oil
Trees seemed to perk up after the stylet and bicarbonate (potassium or sodium didn't seem to make much difference) but nothing got rid of the ghost twigs on the most badly affected varieties.
I hate trying to treat this because it's taking time away from working on whole tree health.
Has anyone encountered this kind of problem? Can you recommend a protocol for cutting down this pathogen? Do I have to engage in radical pruning?

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania
Re: Powdery Mildew
June 12, 2018 02:33PM
There is research on the use of Hops resin acid extracts as an effective counter to powdery mildew (Pseudoperonospora Humuli) . There is a conversation where this comes up in a thread titled Holistic Approach to Fire Blight in this forum if further rabbit holing is desired.

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico
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