As gardeners know, every growing season is different. Spring 2025 brought us:
- Extended dry weather, which can stress plants.
- Damaging high winds that can cause injuries and wounds, leaving plants more susceptible to infections.
- Very few late freezes and frosts, which meant that some blossoms that would normally be destroyed were able to bloom.
- During the blooming period, the weather was warm and pleasant, which meant that the pollinators went absolutely wild.
- The weather has continued to be warm and wet and humid, with frequent storms coming through, including hail which can definitely damage trees.
Unfortunately this has created the perfect storm for diseases, including the incurable bacterial disease fire Blight (Erwinia amylovora – photo), and it has been an issue for area gardeners this year – particularly for those growing pear and apple trees.
See below for a visual explanation of the life cycle for fire blight and how it can move through trees:
The first sign of fire blight is that the foliage (usually near the blossoms) turns very limp and may turn brown or black. The branch around the limp leaves may also turn black. Usually via the blooms (although it can also happen via small stem from things like wind damage), Fire blight gets into the “circulatory” system of the trees and can travel to the trunk, with potentially lethal impacts. Plants will do their best to use their immune system to isolate and stop the disease from progressing, and often that area is where cankers will form. Fire blight bacteria will overwinter inside the cankers. Any infected tissues and the cankers can ooze a creamy sweet sap which attracts insects, the insects then like to pollinate and also crawl on trees. Reportedly, 1 small infected canker can create enough bacteria to severely infect the surrounding plants for 1/2 acre!
While we do select for disease-resistant trees when we order our plants – alas – resistant does not mean immune.
There are 3 main ways to combat Fire Blight (plus a special mention):
1) Pruning, which can be tricky on young/small trees. The general recommendations are to prune 12-18″ BELOW the impacted area, on a dry, sunny day. Be certain to sterilizer your pruners with rubbing alcohol in between every cut, to avoid potentially spreading disease. If your trees are small you can gamble by cutting 6-8″ below the impacted area and watching your plants like a hawk. Discard anything you’ve pruned off by immediately burning it or putting it in the garbage and off your property ASAP. Pruning might seem extreme, but when it comes to fire blight, the stakes are high and the options are few.
- In the dormant season, after the leaves have fallen, scout your trees for dark, sunken cankers and also prune those off as well to stop the spread. Look for smaller ones (smaller than 1″) as well as larger ones. Prune on a dry, sunny day and cut at least 4-6″ below the canker.
- Note: It is exceedingly easy to spread fire blight on equipment!! At a minimum, wipe tools down with rubbing alcohol between every cut. Some sources recommend using multiple tools and rotate using them, letting one soak in rubbing alcohol or 10% bleach while you use the other.
2) Organic – Biopesticides, of which we carry several in stock, and are pictured up top. They do not cure fire blight, but they can suppress it by outcompeting it. There is solid research on the effectiveness behind Bacillus amyloliquefaciens strain F727 (Arber pink bottle), and Bacillus amyloliquefaciens strain D747 (Monterey Complete Disease Control – white bottle). There is also research on the extract of Reynoutria sachalinensis (Arber green bottle) but the interesting thing is that while it works to help plants battle many different diseases, scientists aren’t really certain how it works. If you see any signs of fire blight, start treatment with any of these immediately, however they are most effective when applied as a preventative BEFORE any infection occurs.
- Note which plants had issues this year, and note on your calendar to be certain to spray those with biopesticides starting at bloom time next year, so they can already be on the plant and outcompete any new fire blight (or many other diseases/pests) that might show up.
3) Organic – Organic Copper applied just before the blooms open. Please note that Copper does not seem to work against all strains of fire blight, and may cause fruit to have a russeted appearance.
4) Organic – Thyme Oil. Research has shown that products with 23% Thyme Oil can be quite effective at deterring fire blight. These products must be sprayed when the flowers are open in order to help with fire blight, and then applied quite frequently afterwards, 1-2x per week. Like the Biopesticides and Copper, Thyme Oil is quite fascinating and can actually help prevent a large variety of issues. Due to necessary frequency of application, this is not a very popular option for most home gardeners.
4) Special Mention – there is a biopesticide combo of special yeasts called Blossom/Buffer Protect, however they are not legally for sale in the state of North Carolina! They are available for sale in many states on the west coast and in the northeast, but unfortunately they are currently unavailable for those of us in the Southeast. In order to be effective, they must be applied during blooming. Of all the current biopesticide and/or organic products out there, research shows they have some of the highest levels of efficacy against fire blight.
Many forward-thinking organic fruit growers will use all of the above products in various combinations and timing, in order to figure out what works best for their particular situation.
While many plant diseases are ugly or merely weaken plants, fire blight is something to take very seriously. Timing is critical. If you see issues with your trees, or suspect issues with your trees, take steps to identify what is happening now, as there are look-alike diseases such as some forms of Pseudomonas. Early action now will help prevent future heartache.
Plants Susceptible to Fire Blight (a partial list):
- Amelanchier (Juneberry, Serviceberry)
- Cotoneaster
- Crataegus (Hawthorne)
- Malus (Apple, Crabapple)
- Pyracantha (Firethorn)
- Pyrus (Pear)
- Quince
- Sorbus (Ash)