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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. (https://blogs.cornell.edu/applevarietydatabase/disease-susceptibility-of-common-apples/)
  • -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.


more crops
Apples

Apples

Apricots

Apricots

Asian Pears

Asian Pears

Blueberries

Blueberries

Cherries

Cherries

Currants

Currants

Gooseberries

Gooseberries

Nectarines

Nectarines

Peaches

Peaches

Pears

Pears

Plums

Plums

Raspberries / Blackberries

Raspberries / Blackberries

Strawberries

Strawberries

Unusual Fruit

Unusual Fruit

more crops

Upcoming Events

2024 Winter Fruit Webinars

Event Offers DEC Credits

February 16, 2024 : Week 1: Implementing Mating Disruption in NY Orchards

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.


February 23, 2024 : Week 2: Hot Topics in Food Safety for Fruit

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.


Event Offers DEC Credits

February 26, 2024 : Week 3: Soil Health for NY Orchards

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.


Event Offers DEC Credits

March 6, 2024 : Week 4: Weed Management for Berries in NY

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.


Event Offers DEC Credits

March 11, 2024 : Week 5: Insect and Disease Pest Management for Berries

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.


Event Offers DEC Credits

March 19, 2024 : Week 6: Stone Fruit - Rootstocks and Disease Management

These webinars will provide updates on fruit-related topics and research happening at Cornell University. 

Webinars hosted by NYS IPM Program, CCE Harvest NY, CCE LOF Program, and CCE ENYCHP.

View 2024 Winter Fruit Webinars Details

LOF Advisory Committee Meeting

March 8, 2024
Spencerport, NY

Please join us for our advisory meeting, join the team as they share their current and future projects and programming. Please pre-register by noon on March 5th.

View LOF Advisory Committee Meeting Details

2024 Orleans County - DEC Certified Pesticide Applicator License Pre-Exam Training

March 14, 2024 : DEC Certified Applicator Pre-Exam Training Day 1
Albion, NY

This training is only for those with experience and does not qualify for the 30-hour official DEC training - you are exempt from the 30 hour training (and eligible for this coaching session) if you have pesticide application experience, either through working on your own farm or through employment on another farm.


March 18, 2024 : DEC Certified Applicator Pre-Exam Training Day 2
Albion, NY

This training is only for those with experience and does not qualify for the 30-hour official DEC training - you are exempt from the 30 hour training (and eligible for this coaching session) if you have pesticide application experience, either through working on your own farm or through employment on another farm.

View 2024 Orleans County - DEC Certified Pesticide Applicator License Pre-Exam Training Details

Announcements

Scaffolds podcast

Many of you probably read Art Agnello's statewide tree fruit updates and recommendations newsletter, "Scaffolds". Dr. Monique Rivera is bringing it back, but in a new audio version. Episode one was recorded this week, and is now available for free online at https://podcasters.spotify.com/pod/show/scaffolds


Save the Date! - Scroll down for Upcoming Events

Have you missed a meeting recently? Scroll down for available recordings or pdf links or visits our YouTube Channel https://www.youtube.com/c/LakeOntarioFruitProgram

2024 Events:

23 Feb - Winter Fruit Webinars - Week 2 - 12 - 1:30pm

26 Feb - Winter Fruit Webinars - Week 3 - 1 - 3pm

6 Mar - Winter Fruit Webinars - Week 4 - 12 - 2pm

8 Mar - LOF Advisory Meeting - 10am-3pm, Ogden, Register now

11 Mar - Winter Fruit Webinars - Week 5 - 12 - 2pm

14 & 18 Mar - Pre-Exam Training and Test to Become a Certified Pesticide Applicator - Orleans Co CCE, 8:30am - 12:30pm, Register by March 1st

19 Mar - Winter Fruit Webinars - Week 6 - 12 - 1:30pm

21 Mar - DEC Certified Pesticide Applicator Exam - Orleans Co CCE, Check in 8:30am, Register with DEC

3 Apr - 2024 Respirator Fit Testing - 1-5pm, CCE Orleans County, Schedule Today

4 Apr - 2024 Respirator Fit Testing - 8am - 12pm, CCE Orleans County, Schedule Today

9 Apr - DEC Special Permit Handler Training - CCE Wayne County

10 Apr - DEC Special Permit Handler Training - CCE Orleans County



Food Safety Virtual Office Hours

Cornell Institute of Food Safety "Virtual Office Hours", Tuesdays Noon to 1pm https://cals.cornell.edu/institute-for-food-safety/resources/virtual-office-hours

Past recorded virtual office hours can be found on YouTube: https://www.youtube.com/playlist?list=PLZJs5b7KUuvfcquH3ZtQHo5dSmF2m5MdQ


Webinar Recordings & Additional Meeting Materials

Check out the recordings of some recent webinars and/or conference materials from in person events: Recordings and Playlists are available at https://www.youtube.com/c/LakeOntarioFruitProgram

PACMAN Details and Resources, Meeting Recording Links below:
Developers Conference for Precision Crop Load Management of Apples Playlist - 2024
PACMAN Briefing - 2023







2nd Annual Lake Ontario Fruit Program's Winter Fruit Conference - pdfs


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
https://lof.cce.cornell.edu/submission.php?id=838&crumb=crops|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.​ https://lof.cce.cornell.edu/submission.php?id=799&crumb=crops|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: https://cornell.ca1.qualtrics.com/jfe/form/SV_bEpfAijoP7puQDP

For more information on this survey please visit http://blogs.cornell.edu/swd1/2020/12/02/new-weed-management-technology/


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 https://lof.cce.cornell.edu/submission.php?id=711&crumb=pests|pests.

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