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Powdery Mildew

Posted by Nathaniel Bouman 
Powdery Mildew
November 13, 2017 07:30PM
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 09:33PM
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
Re: Powdery Mildew
October 08, 2019 02:51AM
Had a tough season with Powdery Mildew here in Nassau Count, Long Island NY.. Not surprising, as the humidity was heavy as usual. I'm wondering if anyone has any experience with spraying milk or whey for powdery mildew. I'm told the grape growers are having success with it.

Also, can report that I used pheromones for Oriental Fruit Moth with great success.... It is expensive, but it works.

Tks in advance
Re: Powdery Mildew
October 08, 2019 03:18AM
I’ve tried milk. Started with powdered milk and rehydrated to make “milk” and then added to tank to make a 10% solution. I sprayed early in the PM season and mid growing season. I noticed no appreciable difference, sadly.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania
Re: Powdery Mildew
October 08, 2019 10:43PM
Edited for brevity

Edited 1 time(s). Last edit at 09/30/2022 05:39PM by Chris Vlitas.
Re: Powdery Mildew
October 09, 2019 05:33AM
Just remember that there are different species of "mildews" out there. Not all react the same to "milky" sprays. That said, I know that veg growers have had success spraying a yogurt or whey spray rather than just milk. Its the probiotics that works. In some cases mildews can be superficial, while others can be more invasive meaning that they infiltrate the cuticle of the fruit or veg. For apple, I would begin to work with a stronger probiotic yogurt spray, potassium bicarb or stylet oil (or combo) for better control. Bear in mind that the inoculum overwinters in the bud scales and is first active right after bud break. Start early, don't wait for normal PM weather.

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: Powdery Mildew
October 09, 2019 06:06PM
Edited for brevity

Edited 1 time(s). Last edit at 09/30/2022 05:38PM by Chris Vlitas.
Re: Powdery Mildew
October 17, 2019 02:09AM
My sincere thanks to you all for your advice! I think I will try the SeaCrop in part of the orchard, and whey in another to begin with.... Luckily, I can get whey from our Amish friends, so the probiotics should be intact (no pasteurization).

I will report back next year on my findings

Glenn Aldridge
Restoration Farm
Nassau County, Long Island, NY
Re: Powdery Mildew
June 20, 2020 04:49AM
There is some good research on the efficacy of whey with powdery mildew on wine grapes in Australia. I’ll see if I can find the paper. We do not have issue with mildew but I used whey in a spray last late summer/fall. Go with a very dilute concentration and make sure you get good mixing. It will severely burn pears.

Jim Gerlach
Nashi Orchards
Vashon Island, WA
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