Control of fire blight (Erwinia amylovora) by a novel strain 49M of Pseudomonas graminis from the phyllosphere of apple (Malus spp.)

" A bacterial isolate called 49M, showing protective activity against fire blight caused by the bacterium Erwinia amylovora"


Might as well fight fire with fire I spose.

Michael Phillips spent a lot of time thinking , talking, and writing about the microbiota of the leaf and how you can steer that balance. I always took it to be a little foofy on some level, but I’m more keen on it lately. I was exposed to some of the JADAM and Korean natural farming stuff more recently and it seems like it might be pretty effective and cool overall. It makes perfect sense, really, that culturing beneficial and benign microbes would make it far harder for pathogenic microbes to take hold. Nothing outlandish or earth shattering there.

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It was published 8 years ago, so I wonder if it is in any bactericide products.


I did find this recent article from late April 2023. The author lists current strategies and products and no Pseudomonas products are available that I can see.

He also lists his top strategies in order of use based on growing cycle.

This is how Johnson’s program looks, taking all the data into consideration:

—Starts with Blossom Protect at 80 percent bloom, which prevents bacteria from causing disease.

—Then, shortly after full bloom, he opts for Previsto or another soluble copper (keeping in mind that different products have different levels of active ingredient) “because it’s going to get after those building pathogen populations,” he said.

—At petal fall, fruit marking becomes more of a concern, so that’s the time to use Serenade Opti, which doesn’t cause marking. It doesn’t meaningfully reduce pathogen populations but seems to protect the floral cup “for a couple days and get us through the infection,” Johnson said.

This progression uses each product’s mode of action — protective Blossom Protect, clean-up coppers and defensive Serenade — at the optimum timing. This program, which he considers the organic standard, offers about 85 percent control, comparable to an antibiotic program.

“These are numbers we can live with,” he said, especially because that’s the control in an inoculated trial, where researchers are “coating trees with the fire blight pathogen.”

Are others using blossom protect? I was not aware of it.


The blossom protect sounds promising. Might be worth a shot on my Amelanchier patch, too, which seems to get some shepherd crooked blossom blight. I’d always assumed fireblight, though it stays put at the blossoms. More recently someone, maybe @Richard had posted about blossom blast- Pseudomonas- and I thought maybe a better match for what I’m seeing. Interesting that the microbial you were talking about @clarkinks is actually a strain of Pseudomonas!

In any case, the idea of competitive exclusion on the microbial level has its appeal. Interesting to see it in a commercial product. The organic regime is pretty intense, but then it sounds like fireblight is a tough customer. Glad to not have to deal with it here much if at all.


We see that effective treatment competition for humans in lactobacillus, a lactic acid bacteria that can compete successfully with pathogenic bacteria. Changes pH, competes for nutrients, and alters cell wall, among others.

Glad to hear about this product. I was a little hesitant to spray treatments into blooms this year although I know that’s the right time to do it.

Is this it? Expensive like everything else.



Pricey, yes, but the per tree rate of application seems modest. It looks like a person might need 4 applications per season, which would be 3 teaspoons of the one powder and 21 teaspoons of the other. An amateur like me might find it worthwhile if it were packaged in smaller units.

I’ve been lucky so far and have gotten away without anything other than a few insecticidal sprays and some sulfur.


Last blight year this bad I can remember was maybe 15 years ago. And perfect conditions forecast to continue.



Second year in a row fireblight is hitting hard here. Most of my pears are very or moderately resistant to fireblight. Have a few oddballs as well. Top working many pears to the resistant type.

I am battling fireblight in my little orchard, here in southeastern VA, for the first time. No disease on my pears. (?) Only my apples. And only those quite close to a Pink Lady that has had lots of problems from the time I planted it. I have cut out any signs of fireblight - using the 8-12" down from visible signs of disease. Sometimes I just chose to chop out entire scaffolds. After I ‘butchered’ the trees - I sprayed with copper . . . mixing in some Indar and Streptomycin. I may have to do what I should have done 2 years ago . . . remove the Pink Lady.

I lost many of my developing grafts. I did not get sprays on, when I should have, (snowed under with other things). And the weather was wet wet wet - with a couple of small spurts of very warm temps. We also had some late cold spells. And I have very few apples - and very few peaches. Our pears have not really started producing yet.

Although I continually wipe my clippers, while pruning, with alcohol . . . it is apparent that most of the disease occurred in branches where I had pruned.
It didn’t seem to be present in many of the varieties with less resistance! Just scattered around in pruned branches. So, it is evident that I unknowingly spread the fireblight with my clippers.

Next year I hope to have less pressure preparing for art shows. I will do more dormant spraying - and blossom sprays. I’ll have to ignore my art - and plan better - to allow the time to do this.

There won’t be any photos of beautiful fruit from me this summer. :unamused: One thing that has been validated for me . . . No spray. No fruit.

P.S. - Just wanted to take a moment and wish everyone a lovely Mothers’ Day.
Whether there is a ‘celebration’ or not.
Whether you have a mom or ARE a mom.
Whether your children have 2 legs or 4.
We all ‘mother’ someone . . .
and we deserve a big pat on the back . . . (not to mention a lot MORE!!!)


This is an interesting site. Did not know there was a plant pathology department at tech. I went there (a long long time ago) BTW.


That’s rough. There is a contact time to kill pathogens for any disinfectant, and some disinfectants are less good than others depending on the particular pathogen. You might find this article and included pdf from Dr. Chalker-Scott interesting. The best practice involves a soak time between cuts. Maybe that will help in the future although I wish for you less fireblight pressure next year!


Interesting. Thanks @Buckeye.
I wondered if getting the Lysol, or whatever we are using into the ‘wound’ of the plant was harmful? Guess not. I had lots of that 70% Isopropyl alcohol left, after Covid. So I filled a squirt bottle with it and doused my clippers with it between cuts. Guess that was not good enough.
I plan to only prune during the cold of winter, now. No more summer pruning for me! That may work in CA. But, it sure didn’t help in VA.
Thanks again for the article. - Karen AKA PomGranny



The more i see fireblight the more i graft to resistant varieties. It is one of the most devastating bacteria we encounter growing fruit. As you said the worst part is it steals the harvest.

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I have been spraying regularly but saw fireblight today. I went thru all the trees and cut out any possible strikes. It wasn’t bad but golden Delicious, and Bartlett pear were hit pretty hard. Some parts I cut were probably freeze damage and those limbs were ok.

Today after removing the affected limbs, I sprayed indar and imidan plus strepto with sticker. I know, big guns. I’m going out of town for a week and I wanted to feel like I had protected them as much as possible.

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This is a comprehensive list, but the results are conflicting. Across almost all varieties, different sources list each apple anywhere from highly resistant to highly susceptible and everything in-between.

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Streptomycin or copper etc. wont really do much after bloom.

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I kinda figured as much. A few really late blooms are here and there. I wondered if it might be helpful after pruning out strikes.


The bottom line on resistance for me ) is there are two classes of resistance: notorious “blight magnets” that you don’t want in your orchard; and all other varieties. I have found that blight in this second group can vary by soil, temperature, humidity, region, year, pruning, rootstock, sun, fertilizer and the fates, but overall can be managed with vigilance and the proper blight pruning technique (Prof. Steiner’s “Ugly Stub”).


I’m not sure that your clippers introduced the new infections. Most likely the new pruning cuts just provided a easy entry point for the FB bacteria present in the orchard.

We had the exact same problem after our first big FB outbreak. We followed the guidelines and cut out a bunch of infected branches including the leaders on some 3 year old dwarf trees. Took a pickup load of infected branches to the landfill to make sure they could not provide the source for another big shoot blight infection.

Sprayed some strep and were very surprised when we experienced another major outbreak in several weeks. We experienced a lot rain during this time period.

I called the Apple specialist for my state in a panic who advised me to quit cutting the FB infected branches.

Followed his advice and the noticed a big decline in shoot blight but the damage was done and the trees with a lot of FB never reached their potential.

Apogee really helps manage to manage shoot blight and a lot of research shows it’s effectiveness.

Downside is that is also moderates the growth rate of the trees which can be a problem with young dwarf trees. Some recent research shows a lower dose of Apogee helps manage shoot blight without the reduction in tree growth.

From a 2022 Disease Update:

“Management for the shoot blight stage of fire blight should also begin around petal fall. In order for shoot blight to occur, their must be inoculum present within or near an orchard (i.e. there must be a local inoculum source). Thus, even just a few blossom blight infections or an infected Bradford pear in front of your neighbor’s house can serve as a strong catalyst for shoot blight infection. Shoot blight is the result of infection to young, emerging leaf tissue. Injury to this susceptible leaf tissue provides the means for bacteria to invade and progress down young shoots. Insects with sucking or piercing mouth parts, or other types of wounds created from environmental conditions (e.g. hail, wind, soil abrasion, etc). Application of a plant growth regulator, prohexadione calcium (marketed as Apogee or Kudos) has demonstrated the greatest efficacy against shoot blight in commercial plantings and in research trials. The chemical retards shoot growth, thereby reducing the amount of susceptible tissue available. Prohexadione calcium also thickens xylem cell walls acting as a barrier to the bacterium. At least two applications of prohexadione calcium should be applied during the season for shoot blight management. For mature trees a 12 oz/100 gal rate is recommended at 1-3″ of shoot growth and then 14-21 days later. For trees less than 5 years old in which you are trying to fill the canopy, make applications at the same timings but at a reduced rate of 3-6 oz/100 gallons (again, I’d lean towards the higher rate, especially in trees 3rd leaf or older). Make sure to follow label guidelines on the addition of water softeners and penetrating adjuvant when making an application. Also, do not apply calcium in tank mixture with ProCa.”
WRITTEN BY Dr. Sara Villani Extension Specialist (Apple, Grape and Ornamental Plant Pathology) Entomology & Plant Pathology NC State Extension, NC State University POSTED ON MAY 3, 2022

Read more at: 2022 Apple Disease Update: Petal Fall/1st Cover | NC State Extension