Orchard Outlook Newsletter Vol. 23, No 11

Tuesday, June 27, 2023

Today's newsletter discusses the symptoms of fire blight canker blight that show up at this time of the year at a few weeks after petal fall. Whether canker blight or blossom blight symptoms appear, we explore infection management in terms of product and pruning recommendations. Now that you may be considering lengthening your spray intervals, be careful because fungicide residues are washed off after 50 to 60 mm of rain and stretching spray programs beyond the limit allow summer diseases such as flyspeck to take hold. The ongoing rainy period has delayed application of codling moth control products in favour of maintaining product residue. Thanks to the ongoing commitment of the Orchard Outlook Committee members. 

Table of Contents:

  • 2023 Degree Day Accumulations
  • Apple - Scab
  • Apple - Fire Blight Blossom Blight
  • Apple - Fire Blight Canker Blight
  • Fire Blight - Infection Management
  • Apple - Black Rot
  • Apple - Brooks Spot
  • Apple - Flyspeck and Sooty Blotch
  • Codling Moth: Degree Day and Treatment Timing Predictions
  • Apple Insects
  • Pear Insects

  • Solstice Reminders
  • Weeds and Root Sucker Management
  • Nutrition (Calcium)
  • Cover Crops
  • Mowing
  • Pruning and Training
  • Summer Hedging
  • On-farm Nursery

Events and Notices

  • Virtual Orchard Meet Up Series - Managing the Uncontrollable
  • Apply for Pesticide Certification Online
  • Fuel Charge Exemption Certificate for Farmers
  • International Fruit Tree Association Summer Study Tour in Nova Scotia
  • NSFGA Orchard Tour (Save the Date)
  • Funding Programs

Pest Management Guides 2023

  • Decision Tables
  • Guides



2023 Degree Day Accumulations

Please note that this week's graph is updated to only June 23. Degree day accumulations have consistently been telling the same story this season and that story has not changed. Cumulative degree days are below the 5- and 10-year averages for plant and insect development (Figure 1).

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to June 19 for the past 17 seasons. Provided by Jeff Franklin (AAFC).


Apple – Scab

Primary apple scab infection events in Kentville are complete. There were a total of ten primary infection events observed in Kentville this season with the late April infections being considered light, early May infections were moderate, and late May to June infections were heavy.

Where primary lesions are present, secondary infections have been occurring and will continue during wetting events of sufficient duration. The minimum wetting required for secondary infections is 3 hours less than the wetting required for primary infections.


  • It has now been about 2 weeks since the ascospores were depleted, according to model predictions. Before you consider lengthening spray intervals, take a close look at the leaf canopy in the orchard to determine your risk of secondary infections. Lesions usually first develop on the underside of a leaf and they are velvety brown in appearance. Check cluster leaves for early infections and the mature leaves on terminal shoot growth for mid season infections. 
  • We are again in an extended period of rainfall. Please note that most fungicide residues are washed off by a cumulative total of 50 to 60 mm of rain (2 to 2.5 inches). Summer diseases are a risk if spray programs are stretched to this limit.
  • Be careful mixing water soluble packaging (WSP) with other products. Do not use WSP in a tank mix with boron and rinse the tank well before and after boron.
  • Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting. If petal fall was on June 6, then the there is just over a week remaining for this timeline to be satisfied.
  • The 2023 Fungicide Decision Table can be used to compare fungicide products.

Apple – Fire Blight Blossom Blight

This will be the final notice about blossom blight risk for the season. According to the model, bacterial levels on open blossoms continue to be high. Even if the last antibiotic was applied on June 25 then high bacterial levels would rebuild by June 28. However, it is my understanding that new plantings are now past the bloom stage. If you have blossoms and require further alerts, please let me know.

Ideally you can monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers.

Apple – Fire Blight Canker Blight

There are several recent reports of shoots with ooze that are not associated with blossom clusters. The timing is currently too early for observing shoot blight symptoms. Therefore, it brings to mind a phase of fire blight that we don't often discuss. Within a few weeks of petal fall, bacteria at the canker margins become systemic and internally invade nearby shoots, leading to shoot symptoms that are known as canker blight. 

The canker blight happens yearly in trees where the disease is established in cankers. Often the shoots are mistaken for early shoot blight. But shoots affected by an internal infection have a yellow to orange discoloration of the top leaves just prior to wilting (Figure 2, left).

In comparison, shoot blight arises from the direct infection of the youngest 3 leaves on the shoot and the earliest sign is tip wilt (Figure 2, right). Shoot blight does not show early discoloration of the leaves. Shoot blight does not appear until after blossom blight or canker blight symptoms appear and spread bacteria.

We may observe more canker blight this year than usual for several reasons. Last season there were many fire blight infections that could have formed cankers and are now a carryover from last year. Also, canker blight is very prominent especially if there are no blossom blight symptoms and canker blight is present as the only form of symptoms. 

Please note that varieties considered resistant to fire blight are actually likely to keep the bacteria alive in cankers because the infected trees do not die. Also, cankers that form late in the season are more likely to be active sources of bacteria the following season.

Figure 2: Symptoms of canker blight where internal invasion by the bacteria causes top leaves to yellow (left). Symptoms of shoot blight where infection of the youngest 3 leaves leads to tip wilt and necrosis (right). 

Fire Blight - Infection Management

It may be possible that blossom infections from May 28 or June 1 could be showing symptoms if infections were allowed to occur. According to the model, the infection to rattail blooms on June 14 is not yet visible but will be in the next few days. Blossom blight infections are being reported in New Brunswick where management conditions were quite challenging at the time of infection.

Product Recommendations:

  • As soon as you find fire blight infections and when conditions allow, apply Apogee/Kudos (prohexadione calcium). Use a lower rate if trees have not filled their space or the full rate if tree growth is not an issue. Prohexadione calcium has a rainfast period of 8 hours. The benefits of Apogee/Kudos:
    • Helps suppress the progression of infection to buy you time for cutting it out. 
    • Builds protection in nearby trees that may not yet be infected so that if infection were to occur, the spread would be already slowed. Where infections are numerous, apply prohexadione calcium to the entire block considering that ooze can infect at a distance of at least 0.8 km away.
    • Reportedly has the potential to reduce or prevent canker incidence on perennial wood (Acimovic et al. 2021, Plant Disease; thank you to Ian Willick for sharing).
  • If significant infections are present in young, nonbearing trees, consider applying a copper product when weather conditions allow drying on plant tissues. The copper would help to reduce the presence of surface dwelling bacteria which would reduce the risk of infection if tissues became wounded. Please note that copper will not slow or stop existing infections.

Pruning Recommendations:

    • To save time, it is not necessary to sterilize the tools often as long as all of your cuts are in fire blight areas and during dry weather. Several research studies have concluded a lack of benefit from sanitizing tools. Where there is a tradeoff because of limited labour, it is best to work quickly than to sanitize tools.
    • Do not break off branches with fire blight infections as you navigate the orchard. Research shows that the bacteria becomes systemic in the tree because not enough wood is removed. There are then a high number of new infections and significantly more canker tissue and cankers on structural wood. 
    • Prune out fire blight infections on young trees in the current year, don't wait for winter.
    • Remove fire blight strikes at least 2-4 ft below active infections to remove the leading edge of the bacteria. The younger the tree, the deeper the cut. Being aggressive at the first sign of symptoms will help prevent the re-occurrence of symptoms and the need for continuous cutting back. Repeat tree inspections.
    • If you feel confident that you can monitor the formation of a canker on a stub cut for later removal, then a stub cut may be appropriate. A 4-inch stub cut causes a canker to form on the stub before reaching structural wood like the leader of the tree. However, do not forget to remove the stub because otherwise the canker will serve as a source of bacteria. Mark the tree for revisiting.
    • Cut out infections when a period of 2 dry days are in the forecast. Leave prunings in orchard laneways to let dry thoroughly for several weeks. If cutting a whole tree consider letting it dry while attached to the trellis. Don’t make piles that will prevent the wood from drying.

    Apple – Black Rot


      • The highest risk of infections is between petal fall and 4-6 weeks after bloom.
        • A 10 hr wetting period at 16°C to 32°C allows infection. We do not have a model for black rot infection but protection would need to be targeted prior to wetting and ideal weather conditions.
        • The optimum temperature for infection is 20°C to 24°C. 
        • There are few management options to cover such a long risk period. Captan has activity but note the REI for orchard activities. Merivon has activity but any group 7 + 11 product should not be used more than 4 times each year.  Folpan may have activity but it should not be used until 30 days after bloom.
      • Minimize lenticel cracking by being cautious with spray mixtures (calcium, foliar nutrients).

      Apple - Brooks Spot

      Brooks spot is caused by a fungus that creates sunken, dark green lesions on the fruit. It is a minor disease that has been an issue on Honeycrisp in the past. The symptoms of Brooks Spot can resemble lenticel breakdown and bitter pit which are also common on Honeycrisp. Include a product for cover sprays that is labelled for brooks spot such as Inspire Super and Aprovia Top (or Folpan 30 days after petal fall).

      Apple - Flyspeck and Sooty Blotch

      These summer diseases develop on the surface of the fruit in midsummer until harvest (Figure 3). They are caused by fungi that overwinter in dead twigs and the fungi tend to cause more infections under conditions of moderate temperature, high humidity and rainfall. 

      There is a lag time between when a spore from flyspeck fungi infects an unprotected apple fruit and when symptoms become visible. A certain number of cumulative wetting hours are needed for flyspeck colonies to grow and become visible. Without getting bogged down in the details, the takeaway is that during rainy years the symptoms may be observed early and during dry years the symptoms are less likely. Regardless, adequate fungicide coverage can stop flyspeck colony growth during periods of leaf wetting and may prevent the appearance of symptoms altogether. 


          • Fungicide residues are likely eliminated by 50 mm of heavy rain or 60 mm of cumulative rain. Reapply summer cover sprays before fungicide residue is lost.
          • Fungicides applied after infection can temporarily stop growth of flyspeck colonies but do not cure infections so focus on maintaining fungicide residues. When fungicide residues dwindle below levels that inhibit growth, the flyspeck colonies begin growing again.
          • What if flyspeck growth is arrested all season by consistent fungicide residues and then rains remove residues right before harvest? There is a chance that fruit will not show symptoms if they are harvested and cooled before accumulated wetting requirements. Storage conditions may allow periods of condensation when flyspeck development can progress but development of symptoms in storage is a symptom of already poor control in field conditions.
          • Include a product for cover sprays that is labelled for flyspeck and sooty blotch such as Captan, Maestro, Inspire Super, Aprovia Top, Allegro, Pristine, and Merivon (or Folpan 30 days after petal fall).

          Thank you to Bob Prange for sharing the article by David Rosenberger that I have summarized here. 

          Figure 3: Symptoms of flyspeck infection observed at harvest last year. Summer diseases such as flyspeck are a risk if spray spray programs are stretched beyond the limit. Fungicide residues are washed off after 50 to 60 mm (2 to 2.5 mm) of rain.



          Codling Moth: Degree Day and Treatment Timing Predictions

          The biofix dates for this season are June 2 for early and June 8 for late regions determined by Erika Bent, APM. Jeff Franklin, AAFC, ran the degree day model to predict when degree day thresholds will be met for treatments. The models were run on Monday, June 23 with a degree day threshold of 10°C.

          Codling Moth Treatment with Egg Hatch Products
          Assail, Calypso, Delegate, Intrepid, Altacor, and Exirel
          Timing: The treatment timing for egg hatch products is 100 degree days Celsius from biofix.
          Prediction: The 100 degree day threshold has been met in early and late regions on June 23 and June 24, respectively. 

          Codling Moth Treatment with Organophosphate
          Caution: Newly amended labels came into effect on October 30, 2022. Now all hand thinning activities must be completed prior to application. No hand thinning can occur on trees after they are treated with Imidan. Also, a maximum of two applications may be used each year.
          Timing: Control of codling moth with Imidan is typically slightly later at 140 degree days after biofix.
          Prediction: According to the current forecast, the 140 degree day threshold is expected to occur by June 28 for early regions and June 29 for late regions.


          • Codling moth lay eggs and hatch over a period of time. Late application may miss the first egg hatch and could result in a few codling moth entries. HOWEVER, a heavy rain just after application is more concerning than a late application because heavy rain would wash off and reduce the residual life of the insecticide for all future egg hatch. 
          • Approximately a week after application of an OP insecticide, clean out the trap and start monitoring the trap. The capture of an additional 10 or more moths would indicate that a second treatment is required.

          Apple Insects

          • Choose insecticides by considering what you are targeting and what the products control. Often your hardest to control pest will determine what you need to use, then check the label of that product for all pests that are also controlled by the product. Please refer to the 2023 petal fall insecticide decision table for a quick overview of your choices for apple trees.
          • Monitor for white apple leafhopper. Sevin XLR applications for thinning will control leafhopper but monitor where Sevin was not applied. If treatment is required, the options are Assail/Aceta, Calypso/Theme, Savanto Prime, and Exirel.
          • Monitor for aphids in young trees and nursery plantings where feeding can disrupt shoot growth. If leaves are curling high, high water volumes are needed for effectiveness. Green aphid will move back into orchards that were treated previously so continue to monitor. Assail and Calypso also have activity on codling moth, apple maggot and leafhoppers. Be cognizant of REIs if installing trellis.
          • Mites: European red mite, two spotted spider mite and apple rust mite are the prominent species that affect apple trees. Although not directly damaging to the fruit, these mites in all their motile life stages can drain the nutrients from the trees and dramatically degrade fruit quality. Scout your orchards or check your scouting reports to see if there is a treatable population.
            • Both European red mite and two-spotted spider mite are controlled by the products Acramite, Apollo, Kanemite, and Nealta. All three mite species are controlled by Nexter and Envidor.
            • Mites have many generations per year and therefore have a high potential to develop resistance. For resistance management, it is critical to rotate miticide classes. The use of dormant oil applications will also help to delay resistance selection for European Red Mite.
          • Obliquebanded leafroller: Monitor or check scouting reports for larval populations soon.
          • Apple Maggot: In early years, captures in commercial orchards can occur around July 10th. In blocks that are still being treated for codling moth, the control is extended to early maggot flies. However, in organic orchards, hang traps in early July to begin applications of GF-120 Fruit Fly Bait or Surround as soon as monitoring indicates that flies are present.

          Pear Insects

          • Pear Psylla: Refer to the management guide for product options.
          • Pear rust mite: Pear rust mite can go unnoticed until heavy russeting extending from the base to the top of the fruit. Growers that apply Agri-mek for pear psylla control would also obtain pear rust mite control. Nexter or Envidor would be other options for pear rust mite control.
          • Codling moth: Refer to the above degree day timing given for apples.


          Solstice Reminders

          • Top dressing is not recommended after the end of June. Late release will prevent trees from hardening off before the winter. 
          • Around July the trees are storing reserves in the roots for next year’s growth. When they are storing reserves, late glyphosate applications can be damaging if taken up by root suckers and transported to the root system. Avoid the risk by avoiding glyphosate applications after the end of June.

          Weeds and Root Sucker Management

          • Note that 2,4-D has an 80-day PHI. Eighty days from now is September 15.
          • The recent rain means that Ignite should be avoided until leaf tissue has completely dried off on weeds. Applying Ignite when leaves are wet is ineffective and reportedly does not even burn leaf tips.
          • Broadcasting grass seed is not recommended for establishing grass in the alleyway. Direct seeding is recommended to confine the grass seed to the alleyway and avoid spread to the tree row. The herbicide gramoxone used to provide good control of bluegrass species but post-emerge products for grass control are now limited.
          • Remove root suckers. Suckers compete with the main tree for water and nutrients. They harbour pests, and they are an entry point for fire blight. Pull or break off suckers because otherwise cutting them would let them rebound. AIM herbicide is registered for control of suckers but avoid drift onto young trees and apply only near mature brown bark.
          • Please note there are local reports that the new rootstock G890 has plenty of root suckers and they can show up about 4 ft from the tree.


          • Consider if nitrogen as soon as possible if tree foliage appears pale. Leaching may have occurred during recent heavy rains, especially on sandy soils. Apply a half application of granular nitrogen fertilizer if trees are looking chlorotic. 
          • This year's degree days are tracking similar to those of 2019 and soil temperatures are similarly cool at 30 cm depth. Nutritional deficiencies were observed in 2019 so it is a possibility to keep in mind.

          • Calcium:
            • Note that nutrient product formulations with calcium may contain boron that would interact poorly with water soluble packaging.
            • The goal of foliar Ca sprays is to increase the concentration of Ca in the fruit and reduce the incidence of bitter bit. Begin calcium applications at 4 to 6 weeks after petal fall.
            • Calcium applied at two-week intervals is better than occasional, high-rate applications. 
            • The recommended rate is 4 to 14 pounds of elemental calcium per acre in a season spread over six to eight cover sprays. The percentage of elemental calcium will be listed on the label.
            • Ca has very low movement within the tree and needs to be applied directly to the fruit surface to be absorbed. Therefore, thorough coverage is important to cover developing fruit.
            • Calcium chloride flake (77% Ca) is the most economical Ca material to use but also the highest risk for foliar burn. Apply calcium chloride flake at no more than 4.5 kg per 1000 L of spray solution. The risk of leaf or fruit damage from calcium is highest in hot weather. Susceptible varieties can develop lenticel spotting if damaged. Target fast drying conditions for applications.
            • Risk of leaf injury may be enhanced by Captan. Incompatibility has been observed with Epsom salts, and liquid or emulsifiable pesticide formulations in some cases. Do not apply calcium with Apogee/Kudos.

          Cover Crops

          • Perennia has a series of videos about cover crops by Sonny Murray and Rosalie Gillis-Madden that can be accessed from our website.
          • Summer grasses such as pearl millet and sorghum-sudangrass that have been growing in popularity lately can be planted from mid-June until early August.


          • Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.
          • Mowing and herbicide strips help to prevent issues with two-spotted spider mite (John Michael Hardman).

          Pruning and Training

          • Training practices should be done on dry and sunny days, especially in high risk fire blight blocks. Wounds can take about 2 days to heal. Do not work in trees when they are wet from dew.
          • In dry weather, select strong terminals on young trees and remove competing terminals to single the tops.
          • Young trees are gaining foliage that turns them into a sail in the wind. It is becoming increasingly important to install trellis and tie trees. Prioritize trees that are known to be brittle at the union, including many of the new Geneva rootstocks (G.11, G.41, G.16 etc).
          • Ensure that deer fencing is installed as soon as possible to protect new growth on young trees. Prior to deer fencing, the product Bobbex may be used as a deer repellent but it must be applied proactively and requires frequent application to new growth and after rainfall. Ideally, install deer fencing the year prior to planting.

          Summer Hedging

          • A local study by Perennia in 2013 evaluated the regrowth on summer hedging using Ambrosia on M.9 and Gala. Results indicate that the last week of June = 6 to 21 cm of regrowth, first week of July = 4 to 12 cm of regrowth, and second week of July = 2 to 3 cm of regrowth. No regrowth is expected after terminal bud set around the first week of August although it was not included in the trial.

          On-Farm Nursery

          • Scion leaders need support. Stakes should be placed on the side opposite from the bud so it pulls the bud toward the rootstock rather than away.
          • Monitor for green aphids.
          • Remember the importance of weed control in nurseries. Management practices now will impact the outcome of the final tree. Encourage the growing point to be successful!

          Events and Notices

          Virtual Orchard Meet Up Series - Managing the Uncontrollable

          Since 2021, the summer Virtual Meetup program has brought together growers, researchers, and government and Extension agents to have an international conversation about important tree fruit topics, connecting industry leaders across North America.

          The third webinar series will focus on the topic of “Managing the Uncontrollable”. The first 30 minutes will feature 2 researchers who will introduce the topic, how it relates to tree physiology, and discuss related research. The last hour will feature a grower and speaker panel to discuss practical applications and challenges that growers across North America are dealing with.

          Webinars will be conducted live on Thursdays at 4:00pm (PST)/7:00pm (EST). The format will be an open discussion and in a very inclusive virtual format. Each webinar will last 90 minutes. The program is free of charge. Videos will be made available for those who missed the meetings. Topics and dates: June 29th - Water; July 13th - Heat. Preregistration is not required to attend. Simply go to https://bit.ly/2023-virtual-meetup to join a few minutes prior to the start of each meeting.

          This effort is being conducted across North America in close collaboration with the International Fruit Tree Association (IFTA), the AI Institute for Transforming Workforce & Decision Support (AgAID), and the Cornell Institute for Digital Agriculture (CIDA).

          Apply for Pesticide Certification Online

          The Nova Scotia Department of Environment and Climate Change is pleased to announce that you can now apply and pay for pesticide certifications online. The new online portal is available here:  Online Application (novascotia.ca).

          The change will apply to new applications, re-certification, and applying for certification through reciprocity:
          • New applicants will be able to apply and pay on-line, making it quicker and easier to book an online exam session. 
          • Certificate holders will be able to renew their pesticides certifications on-line, including uploading proof of points and paying the required fees.
          • The on-line portal will also allow applicants to upload of the required documents when applying for recertification through reciprocity.

          If you have questions or run into any issues with the new online portal, please contact your local ECC office. Regional and District Office Locations | Department (novascotia.ca)

          Fuel Charge Exemption Certificate for Farmers

          This certificate permits the delivery of the fuel without having the fuel charge applied at that time. If you are a farmer by the standard of the Greenhouse Gas Pollution Pricing Act (GGPPA) and you carry out eligible farming activities, give the exemption certificate to the registered distributor that delivers the fuel in accordance with this Act. You can find the form here.

          International Fruit Tree Association Summer Study Tour in Nova Scotia

          The Nova Scotia Summer Tour is shaping up to be two fully-packed days of orchards (Honeycrisp, Ambrosia, Gala, Evercrisp, V-trellis pears), apple rootstocks (NC140 trial, on-farm experiences with G890, G202, others), replant trials, new technologies (over-the-row sprayers, Agbot sprayers, Vivid Machines, leaf removal, irrigation, an Eastern Manufacturing equipment showcase, reflective mulch use), growth regulators (thinning trials, Harvest, ReTain), and of course, the usual discussions of pruning, training, and labor issues, plus a lobster dinner with local music! The tour is on July 23 to July 25. Visit their website for more information.

          NSFGA Orchard Tour (Save the Date)

          We will be beginning and ending the tour at the Kentville Research Station, heading west to visit Annapolis County, with some stops in Kings County on the way back. Discussions will include equipment, compost, living labs research and other local research.

          Funding Programs

          Please check the NSDA website for all programs under the Sustainable Agricultural Partnership: https://novascotia.ca/programs/. As this is a new 5-year agreement moving into the Sustainable Canadian Agricultural Partnership programs, producers will need to fill in a new Program Funding Registration Form.

          Pest Management Guides 2023

          All changes new to 2023 are made in red text directly on the guides. The information on all expected changes was summarized in a blog post on March 7. 

          This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Bob Prange, Joan Hebb, Mathew Vankoughnett, Jeff Wentzell, Dustin MacLean, Ian Willick, Karen Burgher, Shawkat Ali, and Danny Davison.

          Perennia Food and Agriculture Corp.
          Edited by Michelle Cortens, Tree Fruit Specialist

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