Apple Scab advice needed

I moved to my new home in Kentucky where I have two older established apple trees. I believe they have apple scab quite bad based on what I saw on them last year.

I pruned and cleaned up the trees bring in more sun and better air circulation, and I sprayed them with Horticulture Oil that I made up myself, and Copper Fungicide.

But after reading over a lot of articles on our forum, I think I also need to spray them with myclobutanil. Is this right? Anything else I can do to get on top of this problem?

John in Kentucky

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I use Rally 40WSP to apply Myclobutanil.
min tbsp / gal = 7.
max tbsp / gal = 11.3.
PHI = 14 days
REI = 1 day
maximum application frequency = 7-10 days.

I wish some of my apples were scabby, it can turn table apples into half decent candidates for hard cider. McIntosh in particular are known to improve significantly (for that particular use) the scabbier they get.

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I’ve read that they are overall more nutritious with some scab as well.

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Link to a study on that subject (it’s in English):

The study found that apples with scab had higher levels of certain anti-inflammatory compounds, apparently as a result of the tree’s immune response to scab infection.

Someone like @Richard would be better equipped to evaluate the study than I am, but it seems worth noting that it compared scab-infected fruit with non-scab-infected fruit of the same susceptible variety (Braeburn).

This makes sense in the context of the study, but it seems to leave open the question of how the levels of anti-inflammatory compounds in a susceptible variety like Braeburn would compare with the levels of such compounds in a resistant variety (say, Goldrush).

In other words, if you’re interested in higher levels of anti-inflammatory compounds, do you actually need visibly scabby fruit, or could you get similar (perhaps even better?) results with resistant varieties that have been scab-exposed?

I guess this would depend on whether the resistance in a variety like Goldrush was based upon the same kind of immune response?

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Captan 50 WP does a good job taking care of scab here.

Where in the hell are you getting those funky numbers from. Using that excessive amount, no wonder your scab is controlled. It also violate the Label is the Law.

ho83.pdf (145.2 KB)

There are so many great-tasting scab-immune apples, consider top-grafting to: Akane, Spartan, Rubinette, Liberty, Ellison’s Orange, Karminj, Rubinette, William’s Pride, Hudson’s Golden Gem.

I’ve tried them all in my scab-prone corner of the PNW. My favorites in order of ripening are : William’s Pride, Akane, Spartan, Rubinette, Karminj, Hudson’s Golden Gem.

I’m still waiting for pears to have such a wealth of great-tasting scab-resistant varieties to choose from!

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The label and the measured density of the powder.

I had that study saved on my documents folder!

The thing to understand is that most table apples are breed to remove tannins, which are polyphenols that make the apples more resistant to fungal infections. One of the working theories for not fertilizing hard cider orchards (one backed by a whole lot of testing) is that it enhances both the sugar concentration and polyphenols as the tree reacts to somewhat stressed conditions.

McIntosh apples are good for blending on hard ciders. The scabby ones can actually pull off a pretty decent single variety cider.

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You would have loved the Macs my Dad grew when I was a kid. He did spray Captan a few times a year, but many of the Macs would still be half covered with scab in bad years. Mom would make apple sauce out of the few that were worth cutting up. I’m pretty sure that tree is why my Dad started cutting down fruit trees and eventually only had a single pear tree left. That Mac was just a huge vector of apple scab.

Thank you everyone for your informative and interesting responses.

I am still trying to get a handle on all of this, so much information.

Rally seems to be good as a protectant, but not sure if it will knock out established Apple Scab. I thought I read something similar about Captan, but I may be wrong.

I have some new trees though that I could try those on. I am looking for something for two older trees right now where the scab is already established.

I did plant one Macinotosh tree, but perhaps that was a mistake. That and a Pink Lady. All the others I planted last year are resistant varieties.


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Here’s another product to consider:

Manzate Pro-Stick Fungicide Label.pdf (319.8 KB)

For Apple the rate is 1.4 Tbsp/gal.