Sharing my quest for controlling fireblight

I don’t really worry about fireblight anymore as the pear cultivars on my multi-grafted trees have been naturally selected to resist it, and I don’t lift any finger to control fireblight. My trees still get hit from time to time, but it can shake it off without even pruning them and they still are productive.

During the early years of apple and pear production in my backyard I did some successful experiments that deal with the fireblight and I need to ask help from you if you can repeat my techniques.

My approach is simple, I used vinegar bacteria to fight off the Erwinia bacteria responsible for fireblight within the flower. Vinegar in its undiluted form is phytotoxic, but not in its very diluted form. My idea was to infect the nectar in the flowers with the vinegar bacteria as the first bacterial colonizer. Once the nectar is colonized by the vinegar bacteria, it makes a toxic environment for the Erwinia bacteria and thus won’t be able to infect the trees during the bloom stage. Other sap sucking insects with deep proboscis can still infect your trees with fireblight. So this approach is to prevent infection through the blooms

This would involve multiplying the vinegar bacteria very inexpensively. So what I did, I bought preservative-free organic raw sugar (sucrose is found in majority of nectars), and created 4 Brix solution (4% by weight, ie mix 5.3 ounces of raw sugar and top off to 1 gallon total volume with sterilized water), then add 1 oz of Cider Vinegar with the Mother (this has the live culture), and aerate it very well with aquarium air pump for an hour. This should multiply the vinegar bacteria rapidly. Then spray on the open blooms every three days, just like you would using the Streptomycin spray. Always make the solution fresh or keep the excess refrigerated to prevent vinegar formation.

By spraying on the blooms, the acetobacter will colonize the nectar, hopefully killing off any Erwinia that may be transferred later by the pollinators. It is needed to spray every three days as new flowers come into bloom or as the nectars are replenished by the fruit trees.

I did this for a couple of seasons on my fireblight susceptible potted trees and they never got infected, but it is a small sample that is worthy of repeat and I don’t have any fireblight susceptible trees as I have given them away. That was about 5 years ago. Maybe you can sacrifice a branch or two and experiment with this approach and later report it here if worked or not. Perhaps observe the type of pollinators that visit the flowers that you sprayed with this concoction, as it could be that the bees don’t want to visit vinegary smelling flowers and thus it doesn’t get contaminated with fireblight.

The plan is to rotate between this method and streptomycin to help prevent the Erwinia bacteria from developing resistance to streptomycin.


I tried along the same concept and I have used compost tea. I also added molasses before spraying it on the blooms and have aerated the compost tea like overnight. It kind of smells like vinegary and I had very low incidence of fireblight on my apples and Asian pears.

I like biological control of pests and diseases, in this case, it’s like probiotics as you are infecting the trees with friendlier microbes before the bad ones get to them.

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That has also been used at controlling other diseases such as mildew and rust!

The new trend of using non-pathogenic (to humans) microbial agents to control other diseases is among the best ones to use and displace the synthetic chemicals. For one, these microbial agents have been naturally occurring and aren’t ecologically disruptive as nature has equilibriated with it, unlike proprietary chemicals whose names you can’t even pronounce. These unnatural chemicals would need several generations or hundreds of thousands of years of natural adaptation so that the world would adapt to it, not the couple of years required by the EPA or FDA to get certificates of safety.

The big AgriChem don’t want to sell live cultures, and you know why? People will only buy once, and they can easily propagate these microbes and use them indefinitely. In fact any live microbial agents can be multiplied easily just using kitchen tools and pantry materials and you can manufacture the microbial agents over and over. Milky spores that control some grubs, you only use them once. Mycorrhizae cultures, you usually only use them once. If you have very big orchards, you can even build larger automated system that you can attach inline on drip irrigations to biologically control your nematodes, and you only buy the live cultures once. No repeat customers… bad for business… but good for our health, the environment and our wallets.

If the government and researchers truly wanted to help, they can help find out what these probiotics or microbial agents are that control various pests and diseases, then sell them instead along with starting nutrient packages and tips on how to multiply them and use them.

There are already many compost tea generators that can be bought at various organic farm trade shows. You can build one for yourself using Home Depot pails. All it needs are the proper microbial cultures that are beneficial to your plants and antagonistic to the pests and diseases.

Several commercial bio-fungicides target Fireblight using naturally occurring bacteria. The two that I’m familiar with are Serenade and Blossom Protect. Serenade contains Bacillus subtilis and Blossom Protect contains Aureobasidium pullulans. Unfortunately the research trials I have seen show that neither product is as effective against FB as Strep, especially in a high FB environment like we often get in the South East. Although they are not as effective as streptomycin they are better than no treatment and are often used in organic production where antibiotics are prohibited

I’m not sure if it would be technically possible to buy the commercial product and replicate the bacteria.

Basic biology. Bacteria thrives on sugar and nutrient media!

Armed but not dangerous.

You will be forever buying these and your pests and diseases will develop resistance to it through time.

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Have your tried the Serenade against FB?

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I used it for about four years. Last year was the only time that I had a few strikes. I’m not sure if it works or not. I used from the original container so it was getting old. Got me a new supply that I will be trying out. Serenade appears to reduce but not eliminate CAR. During bloom I spray about every two days and after the flowers are gone I spray about every week for CAR. I stop using it after about a month. Can’t say for certain that it works but I do think it helps.

Hi! To simply spray the blooms with the cider vinegar doesn’t work? Thank’s!

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I’m skeptical that a home-brew culture would be more effective than products such as serenade and blossom protect that have been developed by years of careful selection and evaluation of organisms that have the best chance to colonize and persist in the flower environment and outcompete FB there. But I sure hope I’m wrong.

You might like this old post Fireblight -conference pear? - #16 by clarkinks. Back in 2015 and years prior I saved some trees with vinegar I believe as noted here Recurring Problem Pears Every Late Summer

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