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Winter pruning to manage fire blight (while continuing to grow the trees)

February 23, 2021

By Janet van Zoeren, Kerik Cox, Anna Wallis and Mario Miranda Sazo

Winter pruning is always an important time to begin your fire blight management program for the season, and this year especially much so. Winter canker removal could make the difference for you between starting spring 2021 with "normal" fire blight pressure, versus potentially giving yourself a handicap by keeping around lingering bacteria from last year's difficult season.

Here we discuss some reminders of how and when to prune for fire blight management, and some tips for how to continue to grow the trees in areas with more severe damage.

Winter/Spring pruning in 2021: Remember that Erwinia amylovora bacteria can only survive in the orchard on or inside of living tree tissue, particularly at the margin of cankers. So, the more cankers you remove now, the less bacteria you will have to contend with in the spring.

fire blight canker beginning to ooze in the spring.

Keep your eyes open (and train your crew to keep an eye open) for cankers in all blocks as you are pruning this winter. Hopefully you marked on a map or flagged areas of high fire blight pressure last summer, so you can pay especially close attention for cankers in those areas. In blocks with high pressure last year, we recommend taking a few extra passes down those rows, focusing just on looking for cankers without the distraction of general pruning decisions.

Fire blight cankers appear as dark or black, cracking "scorch marks" on the bark, and often the leaves or leaf stems remain on the tree through till spring. These may not be oozing, but do not discount them.

When deciding where to cut when removing a canker, we recommend you use a hatchet or knife to peel bark away from the tree until you see healthy green tissue. Make your pruning cut approximately 4 inches into 2nd year wood. If the canker is in older wood prune 10-12 inches before the edge of the canker. If there are too many cankers in a block to warrant that level of detail, you can instead simply make the cut 3 feet before the canker in young vigorous trees, and 18 inches before in older slow-growing trees. In all cases, cutting beyond different ages of growth is the best practice as the fire blight pathogen moves across junctions between new and older tissue more slowly.

For trees 2 years old or younger, it is often safer/ to just pull the entire tree and replant later.  For example, in the pear orchard image below, trees struggled with fire blight throughout the 2019 growing season. All trees were removed in winter 2019/2020, and roots were excavated by early April 2020.

When the tree is growing, the bacteria will be moving and growing. During winter both the trees and the bacterium are dormant, so cuts can be made safely and equipment sanitation is not a concern. Make sure to remove cuttings or let them dry out in the orchard over the course of the remaining winter months. By the time temperatures reach ~40F, Erwinia bacteria will begin growing.

Several mature pear trees had to be removed due to high fire blight pressure the previous season. Roots were excavated to prevent oozing and further contamination.

Prioritizing blocks by Evaluating risk. Take a good look at your orchard and the specific blocks within your orchard. Not every block will require the most aggressive management, and frankly, there isn't enough time to provide vigilant scouting and management to every tree or every row. Prioritize blocks *you may even consider ranking them* and tailor your management (this winter and during the growing season) based on characteristics that will contribute to likely disease pressure.

  • -Disease pressure: Did this block have fire blight last year? Has it ever had fire blight? If not, it is a very low risk block and requires less management.
  • -Variety and rootstock: Evaluate the susceptibility of the cultivars planted in each block and where possible include resistant varieties in new plantings. (
  • -Tree age and planting system: Newly planted trees and high-density systems are at much higher risk of quickly being devastated. These trees have vigorous shoot growth, which is most susceptible to fire blight. In smaller trees, fire blight can quickly travel through the vascular system to the central leader, killing the tree, or travel systemically to the rootstock, girdling and killing the tree.


Tips to maximize safe grow of a new 2021 leader in a young tree that was heavily pruned due to FB in 2020:

For trees that were pruned back aggressively in the spring of 2020 to slow spread, we expect that a healthy tree will respond by growing many new shoots in 2021. To keep the tree growing vertically, the new shoots can be pruned to a single shoot (trained as a new central leader), to continue growing the young tree in newer plantings or to rapidly reach mature height in older plantings. For older plantings, the selected shoot should be of medium vigor without side shoots, hopefully with fruit spurs that will produce apples that will bend and weaken it in subsequent years. In the case of young trees that were heavily pruned and tree height was significantly reduced, we recommend you salvage tree structure and reconstruct it by selecting and training the most optimal shoot where the leader was cut off. If the trees are too devastated by fire blight, it may be less frustrating to replant than try to retrain. If you do decide to retrain, try to choose the new leader so that it keeps the best possible vertical positioning of the old trunk section. 

  • -Select the new leader when 2-4" long and cut competing shoots back with clippers to 2" long to prevent competition with the leader
  • -Train the new leader to the wire (ideally also to a vertical element 'bamboo', 'plastic twine', 'wire') with a rubber band, tape gun, or a wire loop as soon as it reaches each successive wire
  • -Apply 2-3 small doses of nitrogen to gently promote growth of the tree in 2021
  • -Use of PGRs can also promote 'vertical growth' of the new leader when trying to reconstruct a heavily pruned young tree due to FB (Promalin will promote maximum vertical growth/less feathering. MaxCel will promote better tree feathering/less vertical growth.)
  • -Water the trees (when needed) using trickle irrigation with low doses per tree but frequently
  • -Remove flowers manually or chemically
  • -If planning to crop the young tree in 2021, the unsupported terminal portion of the new leader above the last wire should be de-fruited for maximum shoot growth and good lignification during years 2, 3, and 4
  • -Pay close attention for signs of fire blight (train your crew for early detection), especially in blocks that are being pushed to fill space (with aggressive nutritional programs).
  • -If the tree doesn't respond to the above practices, it may be worthwhile to replace the tree to ensure that it doesn't become a source of fire blight in the coming season.

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Upcoming Events

How Profitable Will My New Orchard Investment Be? 1-day, hands-on skills class

February 7, 2023
Highland, NY

The Eastern NY Commercial Hort Team and the Lake Ontario Fruit Team are offering a 1-day, hands-on course at 5 locations in NYS in January and February for tree fruit farms on using farm financial information and other resources to make decisions about long-term investments or changes to their business.  We will apply the techniques covered in the 8-part webinar series in December to scenarios using sample financial data from fruit farms in NYS.

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Apple Leafcurling Midge IPM - Webinar

Event Offers DEC Credits

February 16, 2023

In recent years, the apple leafcurling midge (ALCM) has become an increasingly problematic pest in many orchards across the northeast.

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Western NY Fruit Conference - "State of the Industry"

Event Offers DEC Credits

February 27 - February 28, 2023
Henrietta, NY

CCE-LOF are excited to bring you a muti-day fruit conference in WNY! This is replacing our Winter Fruit Schools. Tentative Agenda is now available.

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Save the Date! - Scroll down for Upcoming Events

Have you missed a meeting recently? All recorded LOFP hosted webinars can be found on our YouTube Channel

NOW - please scroll down to find the link to the short NY Herbicide Resistance Survey!

Courses Available All Year - Cornell Small Farms Program New Season of Online Courses-Enroll Now!


2-5 Feb - NOFA NY Virtual Winter Conference

8 Feb - Becker Forum - All Day - Oncenter, Syracuse

12-15 Feb - 66th Annual IFTA Conference & Tours - Grand Rapids, MI - $650

16 Feb - Apple Leafcurling Midge IPM - Webinar - 1:30-2:30pm - Registration Now Open

27 & 28 Feb - WNY Winter Fruit Conference - Registration Now Open

7-10 Mar - 2023 Annual Meeting & Conference of the 10th NASS & NASGA - San Luis Obispo, California

14 Mar - USDA/RMA Listening Session - Spring 2023 Apple Grower Meeting -
The Risk Management Agency (RMA) is inviting interested parties to participate in a listening session to discuss the proposed changes to the apple crop insurance program. Free - Rochester

14-15 Mar - Curso de Desarrollo de Liderazgo - contact Tim Shenk

15 Mar - Fire Blight Informational Webinar Series - Using biopesticides to help control fire blight - 7-8PM

16 Mar - CCE Stone Fruit Updates Webinar - registration coming soon

17 & 21 Mar - Pre-Exam Training to Become a Certified Pesticide Applicator - Wayne Co CCE - $50

21 Mar - Strep Resistant Erwinia amylovora in New York States - 1-2:30pm, virtual, registration coming soon

24 Mar - Test to Become a Certified Pesticide Applicator - Wayne Co CCE - $100 

13 Jun - Fire Blight Informational Webinar Series - Pruning and sanitation strategies to reduce fire blight - 7-8PM

18 Oct - Fire Blight Informational Webinar Series - Using weather and environmental conditions to optimize biologicals and biopesticides for bloom production - 7-8PM

Food Safety Virtual Office Hours

Cornell Institute of Food Safety "Virtual Office Hours", Tuesdays Noon to 1pm

Past recorded virtual office hours can be found on YouTube:

Webinar Recordings

Check out the recordings of some recent webinars:


Employment Opportunities

The CCE-LOF Program has created a space to share Lake Ontario Fruit Region local employment opportunities. See listings and details for sharing listings at|business

Pollinator Resouces

Now available Pollinator Resource Links

Meeting Recordings Now Available

Did you miss the recent meeting?  Check and see if we recorded it and added it to our website or Lake Ontario Fruit Program YouTube Channel.

Honeycrisp Meetup recordings available here.

Why are my trees growing so poorly? recording available here.

Additional Recorded Webinars listing with recording and resource link are available at|crops|apples|crop*38

New Publication on Growing Pawpaws

Are you a fan of pawpaws? These custardy fruits can be hard to come across, so this guide provides information on how to grow your own pawpaw from seed, and how to care for grafted seedlings. Pdf on growing now available.​|crops|unusual_fruit|crop*50

New Weed Management Technology Survey

Want to move away from herbicide reliance? Are you using novel technologies to manage weeds? We want to know about it to inform our weed science research. A team of weed scientists from University of California Davis, Oregon State University, and Cornell University are asking berry, tree fruit, tree nut, and vine crop growers to take 5 to 10 minutes and answer this short and anonymous survey. Weed Technology Survey link:

For more information on this survey please visit

Pollinator Webinar Series - Summer 2020

The Pollinator Webinar Series presented by Penn State cover bee health and pollination services.

Bloom Pesticides for Pollinator Health

A reference table created by Janet van Zoeren and Anna Wallis, is now available at|pests.