New England: This Years Apple Scab Control

Hello from Massachusetts. New member here finding all sorts of great info on this forum. Here in New England we’ve had rain almost every other day this spring causing issues with any sort of spray schedules. What are other local Apple growers doing for scab control this year?


Best thing I can think of is using a sticker with my fungicide spray

There are a bunch of us in MA from Cape Cod, @Johnthecook, to South Shore, @Courtney, to suburb @HollyGates and @SMC_zone6 to central MA me and @galinas and a couple in the Berkshire @JinMA and someone else I could not recall at the moment.

Where are you in MA?

@mrsg47 is in RI. @alan has a good spray program. He’s in NY.

I use Immunox for both CAR and scab. Timimg of spraying is as important as what spray you use.



To add on to what you say Tippy, is spraying cannot be undertaken under rainy conditions and this time of year for us is always difficult. I usually wait until noon, the following day of rain and check to see if the trees are dry then spray. Rain is our enemy right now. To me anyway!

It’s been hard here to find a dry slot

I prefer to spray before rain, if there’s enough time for it to dry

Great info everyone, thank you! I’m in Stow. Looking forward to learning more from everyone here.


You should list your state in your profile. It will help people give you better advice if they know your state.

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My apples are still blooming, but I’ll follow @alan’s spray schedule again this year once they finish up – if it ever stops raining. It works well and seems to be a good comprimise for wanting to eat close to organically but understanding the realities of what organic would mean in this climate.

Hi Rob,

Welcome to the forum! Like mamuang said, I’m out in Western Mass, though not quite up in the Berkshires (Pioneer Valley). And yeah, definitely a lot of rainy days lately, though sunny this morning where we are.

My trees are pretty young yet, with the oldest starting their third year from bench-grafting. I definitely have a lot to learn, but at this point my strategy (such as it is) has been to select varieties that are supposed to have some degree of disease resistance, train them in an espalier to increase sun exposure and air circulation, keep the leaves and things cleaned up as well as I can, and see what happens. (Some of you may have seen this movie already, but no spoilers, ok?)

Part of this is due to having a small yard with neighboring houses (not to mention our own house) within a few feet of where I’m growing trees, so spraying would be difficult in any case. If I were to start spraying, I would probably start with the guides that Alan and Scott have put together and try to figure out from there what might make sense for me.

Honestly, though, there are quite a lot of unsprayed and even entirely untended apple trees around where I live that look to be acceptably healthy by my standards, and I’ve picked plenty of wild apples that were acceptably sound (again by my standards). If my own trees do as well, I will be quite happy. And if they don’t, I guess I’ll decide what to do when I get there.

As far as scab goes, I really haven’t seen much sign of it yet, though the trees are still young. I did have some issues with CAR last year, but that’s primarily an aesthetic issue, from what I understand. We’ll see how it goes this year.

Best of luck to you and your trees!

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For ignorant eastern MA resident like me, anything west of the Worcester county is the Berkshires :smile:


Just like I think everything east of the Quabbin is Boston (or Cape Cod)…


The scab fungus feeds on the amino acid arginine, found in apple leaves. Apple trees only have arginine in their leaves if they do not take up enough cobalt from the soil to process the arginine further.

Apple varieties which are ‘immune’ to scab are very good at uptaking cobalt, and have no arginine in their leaves for the scab fungus to feed on. The varieties prone to scab do not get enough cobalt from the soil.

I purchased liquid cobalt from Advancing Eco Ag last year, and sprayed it on my trees every couple of weeks. Varieties like Honeycrisp and Zestar, which had heavy scab the year before, were clean last year.


I urge caution about reading too much into anecdotal experience- I tried to find research data on cobalt’s efficacy on scab and came up with nada.

While it’s entirely possible it works, you at least need to employ a control before you can assume the cobalt was the reason for your good fortune. That would have been easy enough if you’d just left a few pairs of varieties with one untreated.

If you have any links to research that support your conclusion, please let us know. If it works, it will be adopted by the entire commercial apple industry in the humid regions. Most scab killing chemicals lose their efficacy in commercial orchards after a decade or two. It costs millions of dollars to bring replacement products into the market place.


I’ve also seen a video by the Michigan State University tree fruit pathologist about the same thing. I have no idea if they’ve done any research or not.

Personally, I have no desire to use any type of poison in my garden or orchard. Spraying a fungicide on my trees may prevent scab, but how much of the beneficial fungus in my soil will be killed as well? Just as I choose not to spray insecticides, because I don’t want to harm the beneficials.

I’ve adopted the philosophy that the healthier my plants and trees are, the stronger their immunity against insect and disease pressure. It’s been working for me so far.

Here’s a possibly interesting article about reducing scab sprays from UMass. Directed at commercial orchards, but suggests that shredding/cleaning up leaf litter can very significantly reduce the presence of scab spores, particularly early in the season.

Cobalt is a fairly toxic metal, so it also stands to reason that the cobalt spray may well just be preventing scab by killing the spores. My hypothesis is that you could probably achieve the same result by spraying with copper sulfate. Though it is probable that Co(II) is much less toxic to the plant than Cu(II).

I’ve tried this spray, which is copper mixed with two nutrients - methionine and riboflavin. My fungicide fail
Which is based on a published scientific report: Sprays for Apple Flyspeck and Sooty Blotch

It caused fruit russeting, and I pulled back on it and used a synthetic to control sooty blotch/flyspeck. One application of that and Pristine (a Bonide product containing it) gave me season-long control of those summer diseases.

In 4B it doesn’t surprise me that you don’t need a lot of intervention. The longer, more humid and warmer the season the more pest pressure there is.

That is some interesting information and the experiment was a long time ago. It is interesting that Cornell hasn’t followed up on it given all they’ve done to help commercial organic apple growers in NYS. Do you know of any follow up studies on this?