Orchard Outlook Newsletter Vol. 23, No 7

Tuesday, May 30, 2023

Today's newsletter discusses recent information on precipitation and dry conditions. We review peach bud growth and how the winter injury influences pruning decisions. With plenty of blossoms still present, fire blight blossom blight is still top of mind; please note that bacterial populations are either currently high or will soon be high and wetting could trigger infection. Varieties considered susceptible to fire blight still have pink buds so do not underestimate the risk of infection on late flowers. Fruitlet thinning will occur soon so we consider approaches. Thanks to the ongoing commitment of the Orchard Outlook Committee members. 


Table of Contents:


Weather
  • 2023 Degree Day Accumulations
  • 2023 Precipitation
  • Apple Bud Growth
  • Peach Bud Growth
  • Apple - Scab
  • Apple - Powdery Mildew
  • Apple - Fire Blight Prevention
  • Apple - Fire Blight Blossom Blight
  • Fire Blight - Shoot Blight Management
  • Apple - Calyx/Blossom End Rot
  • Apple - Black Rot
  • Pear Insects
  • Stay tuned for apple insects

Fruitlet Thinning

  • Influence of Weather
  • Apple Fruitlet Thinning
  • Defrosting Young Trees
  • Pear Fruitlet Thinning

  • Grafting
  • Mowing
  • Pruning and Training
  • Fertilizing
  • On-farm Nursery

Events and Notices

  • Funding Programs

Pest Management Guides 2023



 

Weather


2023 Degree Day Accumulations

Cumulative degree days continue to be slightly behind the 5- and 10-year averages for plant and insect development (Figure 1). The lack of heat equates to plant growth being about 2 to 3 days behind average. The average temperature for May is 10.2°C compared to the 10-year average of 11.2°C. 

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 29 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 8% less plant development heat units compared to the 5-year average, and 9% less compared to the 10-year average.
  • Approximately 22% less plant development heat units compared to 2022, and 21% less compared with 2021.
  • Approximately 10% less insect development heat units compared to the 5-year average, and 15% less compared to the 10-year average.


2023 Precipitation

The Kentville weather station has recorded less than half the monthly average rainfall at 31 mm out of 74 mm. Jeff Franklin assembled the total precipitation for the months of April and May, for Kentville, over the last 111 years and sorted from lowest to highest. The 10 driest years are shown in Table 1 and 2023 ranks as the 5th driest year. The weather has been noticeably dry but having temperatures below average has helped because evapotranspiration is lower than it could be.

Where possible, newly planted trees with shallow root systems would benefit from irrigation. Less obvious is how the moisture deficit is impacting established fruit trees with deep root systems. Dr. Vicky Lévesque has collected data that says the soil in several orchards at 30-50 cm depth is currently similar to or less moist than the top 0-30 cm. It would seem that the minor wetting events have watered the topsoil but did not percolate to depth. Also, sandy to coarse loam soils in orchard are generally at lower levels of water content than loamy soils, as expected.

Table 1: Total precipitation for the months of April and May in Kentville over the last 111 years, showing the 10 driest years. Provided by Jeff Franklin (AAFC).

There are currently some very good programs available to cost-share your improvements to water resources. 



Tree Growth


Apple Bud Growth

An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on May 29, the Idared buds were at the 50% petal fall stage, Honeycrisp was at early petal fall and Ambrosia was at late full bloom (Figure 2). Orchard Outlook committee members also report that varieties are slightly further behind in Morristown, similar in Falmouth, and a little further ahead in Melvern Square. Terminal shoots are elongating and should be within the window of 2.5 to 7.5 cm for the first application of Apogee/Kudos. 

Figure 2: Bud growth in an early region on Middle Dyke Road in Kentville on May 29. Shown from left to right: Idared, Honeycrisp, Ambrosia.


Peach Bud Growth

Pruning peach trees is going to be a different process this year. There are questions about where, when and how to prune. As a result of winter injury, many vegetative buds were damaged and the trees are left with sections of dead wood (Figure 3). The dead wood should be pruned off the trees to the next closest live shoot toward the main stalk. 

Peach trees recovering from cold injury are still best pruned around typical bloom time. Pruning much later than normal will remove some of the leaves in which the tree has already invested reserves. 

Experience from other regions that experience cold injury suggest avoiding severe pruning. The tree is healing from winter injury so limit your pruning to no more than 25% to 33% of the tree's branches. 

Whatever you do, don't skip pruning this year. Peaches fruit on one year old wood so each year the fruiting zone moves higher and higher in the tree. Without pruning, the tree will be taller but with less production and with tufts of shoots creating shading in the fruiting area.

Continue fungicide protection for leaf curl and peach scab and monitor for feeding insects like aphids.

There is a good article about cold damage by the Good Fruit Grower in 2020.

Figure 3: Vegetative growth on peach trees following winter injury show sections of damaged wood encircled in red. Photos contributed by Danny Davison.



Diseases


Apple – Scab

No apple scab infection events were recorded within the last week.


Recommendations:

  • Ascospore maturity is currently at 96%. According to the forecast, total seasonal ascospores are expected to mature to 99% by this coming Saturday. 
  • We continue to be in a very high risk period because many spores have matured since the last rainfall. The next apple scab infection will have a significant spore load of about 20% available. 
  • Apply a protectant fungicide to green tissue prior to an infection event on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth. 
  • Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
  • Remember that there is a new label for Manzate (mancozeb). The product may be applied 4 times/ha/year, the re-treatment interval is 7 days, the REI for hand thinning is 35 days (12 hrs for all other activities), and the PHI is now 77 days.
  • Alternatives to Manzate for resistance management? Captan may be applied if it is not 7-14 days within an oil. Allegro may be applied 1 day after an oil.


Apple – Powdery Mildew

Powdery mildew infections can be expected when conditions are warm (10-25°C), humid and dry.

Recommendations:

  • Where powdery mildew pressure is historically high, a third application is often recommended by petal fall. Apply prior to a period of warm and dry weather. 
  • Remember to treat young plantings because severe infections can reduce shoot growth, which is most concerning for young, non-bearing orchards.
  • Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.
  • Practice resistance management:
    • When groups 3 & 7 are used, careful consideration must be given to rotating the groups to slow resistance development. Avoid more than two consecutive applications of a single group.
    • Scab: Although Group 3 fungicides Nova and Fullback are also labeled for apple scab, they are not expected to provide control because of resistance in the local scab population. Another product is required for scab protection.


Apple – Fire Blight Prevention


Recommendations:

  • Do not pinch flowers due to recent conditions. Bacterial populations have had heat needed to grow on flowers throughout the Valley. Creating wounds and touching flowers carries a risk of spreading bacteria.
  • Pruning practices should be done on dry and sunny days, especially in high risk blocks. Wounds can take about 2 days to heal. Do not work in trees when they are wet from dew.
  • Be cautious when applying post-emergent herbicides to prevent injury to young trees. 


Apple – Fire Blight Blossom Blight


Monitoring for Blossom Blight Alerts
All NSFGA-owned weather stations are being used for industry monitoring and alerts. Alerts will be delivered to subscribers on weekends and holidays. Ideally you will also monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers.


Current and Forecast Blossom Blight Risk
  • Several alerts were sent for the risk period on Sunday, May 28. Several showers and the risk of dew warranted post-infection control with streptomycin on Monday, May 29.
  • Streptomycin applied on May 29 is expected to provide protection until Wednesday. On Thursday, June 1 the EIP that represents bacterial growth on open flowers is again expected to be high. Wetting will trigger an infection. Do not spray high water volumes on trees in bloom unless an antibiotic has been applied.
  • If no streptomycin was applied on May 29, the risk varies but generally the EIP is high and infection is possible today and for the next three days for apples and pears.
  • There are too many unique scenarios, don't hesitate to call me for more information.
  • Stay tuned because predictions can change on short notice.

Recommendations:

  • If you are due for a fungicide at the end of the week, don't spray without antibiotic protection. This coming bacterial risk might be a good opportunity to use Kasumin for its short REI if you apply it before the rain and in the evening. However, remember it needs to be applied a few hours before rain.
  • Agral 90 is a recommended tank mix with Streptomycin or Kasumin and Apogee or Kudos. It reduces the surface tension allowing liquid to spread evenly across leaf tissue for better coverage. Without it, there are large droplets that spread less evenly. Agral 90 also breaks down the waxy cuticle allowing chemical uptake. 
    • Manzate is a formulated product that has spreader sticker activity so if it's used with Streptomycin or Kasumin, then reduce the rate of Agral by half. 
    • There is no direction from the Agral 90 or Captan label for Captan toxicity. Oils and spreaders can enhance uptake of Captan which kills cells on entry. Allow a period of time between Agral 90 and Captan application. The Agral 90 is a lower rate than Superior oil applications, but go based on your experience.
  • Varieties considered susceptible to fire blight like Paula Red and Gala still have pink buds. Their long period of bloom with flowers opening successively is in part responsible for the increased risk of infection. Do not underestimate the risk of infections on late flowers.
  • Streptomycin 17 will provide excellent efficacy on blossom blight and is best used up to 24 hours prior to an infection event. If necessary, it may be used after infection and is best used within 20-24 hours. It is recommended that you keep Strep on the farm at this time of year to respond quickly. Streptomycin 17 may be used up to 3 times each year.
  • Kasumin also has excellent efficacy and may be used up to 4 times each year during bloom. Consider using Kasumin if you need to re-enter a block because it has a short REI of 12 hours. However, the PHI for Kasumin is 90 days, which can be challenging for early varieties like Paula Red. Note that Kasumin is not partially systemic and should not be used for post-infection control or after a trauma event.
  • For on-farm nurseries, consider applying a copper product at the lowest labeled rate prior to training trees and follow the labeled REI. Make cuts on only dry and sunny days.


Fire Blight - Shoot Blight Management


Recommendations:

  • Apogee should be put on with higher water volumes to cover all new leaves and growing tips.
  • Apogee is applied dilute so be aware of the fire blight blossom blight risk at the time of application. If the EIP is high, the bacterial population is high and a dilute spray may cause an infection.
  • Apogee/Kudos (prohexadione calcium) supress shoot blight. The timing of the first application at 2.5-7.5 cm of new shoot growth is critical to success. Follow up with a second application applied around 14 days later.
  • Include Agral 90 at 500 mL per 1000 L of water. Do not exceed this amount of surfactant. If applying Agral 90 there may be a risk of burn if using Captan.
  • Apogee should also be applied with spray grade ammonium sulphate (AMS) in an equal 1:1 ratio with the amount of Apogee used (e.g. 500 g Apogee = 500 g or 0.5 L of ammonium sulphate). This is not the blossom thinning product ammonium thiosulphate (ATS)!


Apple – Calyx/Blossom End Rot


Recommendations:

  • If calyx/blossom end rot has been an issue in the past, consider using a captan product during full bloom. Infections can occur in problem blocks as the pathogen can last in the soil for several years.
  • If applying Streptomycin with Agral 90 there is a risk of burn if using captan. Prioritize fire blight over blossom end rot.
  • Keeping grass and dandelions mowed will allow the soil to dry and reduce the environmental conditions for spore ejection. Other broadleaf weeds are also a host of this disease so weed control prevents the build up of this pathogen.


Apple – Black Rot

Recommendations:

    • Based on our limited knowledge, the highest risk of infections is theoretically between petal fall and 4-6 weeks after bloom.
    • Black rot can survive on prunings. Flail mow prunings in row middles where they will degrade more quickly.
    • Minimize lenticel cracking by:
      • Avoiding drought stress with irrigation
      • Being cautious with spray mixtures (folpet, calcium, foliar nutrients). Be especially cautious when heavy rains follow drought conditions because rapid fruit expansion can break lenticels and allow product to cause more damage than usual, making it susceptible to fungal infection.
      • The black rot fungus infects fruit during warm rains from petal fall to harvest: A 10 hr wetting period at 16°C to 32°C allows infection. 


    Insects


    BE RESPONSIBLE FOR POLLINATORS – DO NOT SPRAY INSECTICIDES DURING BLOOM!

    • Fungicide, antibiotic, and growth regulator sprays are best applied early morning or late evening when bees are not actively foraging. Be aware that dandelion blooms are open until about dusk.
    • I am actively working on a new decision table format for the petal fall/calyx stage insects. Please stay tuned.

    Pear Insects

    • Petal fall is the ideal treatment timing for winter moth and fruit worm in pear. Treatment should be based on need determined by monitoring. 
    • Apple curculio is difficult to monitor for and its presence often is not observed until damage on fruitlets shows up. Treatments for this pest should go on when pears have reached petal fall. Use of one of the products registered for plum curculio should also control apple curculio.
    • If you are planning to use Agri-Mek + Oil for pear psylla control, it is best to apply it at petal fall or ideally within 2 weeks. Agri-Mek has better residual control when applied to younger tissues. 
      • Do not apply Agri-Mek with any bloom around as this product is highly toxic to bees. 
      • Do not use Captan/Maestro as a fungicide for pear scab within 14 days of Agri-Mek + Oil. 
      • Do not use MaxCel in close proximity to AgriMek because the oil will increase thinning activity.
      • Minecto Pro (Abamectin and Cyantraniliprole) is a new formulation that is registered for control of pear psylla with the same recommended application time.



    Fruitlet Thinning


    Influence of Weather

    Moisture stress can increase thinning activity. However, at this time it is unclear whether established trees are undergoing moisture stress. You might have noticed that 2010 was also a very dry year so review your records on thinning outcomes from 2010 to help inform your choices this year. There were possibly higher levels of natural thinning at that time.

    Temperature and sunlight also influence tree sensitivity to chemical thinners. These factors 2 days before and more importantly the 4 days after applying thinners determine thinner response. The relationship has been explained in terms of the carbohydrate status of the tree. During sunny days the tree is photosynthesizing unimpaired and when matched with cool nights (<18°C) it is respiring slowly, meaning carbohydrates are plentiful. Reversing the conditions, cloudy days impair photosynthesis and when coupled with warm nights the respiration uses many carbohydrates making them in short supply, causing stress to weak fruitlets.
    • When we reach petal fall, expect fruitlets to grow about 1 mm each day in average temperatures.
    • The optimal temperature for thinner activity is between 21-24°C (within fruit sizes of 5 to 18 mm and most effective from 7-12 mm).

    Apple Fruitlet Thinning


    Fruitone L:
    • Strong thinner that is very effective in Nova Scotia and is rate-responsive.
    • Unabsorbed residue on leaves is inactivated by sunlight. Slow drying conditions cause more absorption. Therefore, nighttime applications are usually more effective.

    MaxCel/Cilis Plus:
    • Product is most likely effective when weather conditions cause carbohydrates to be limiting. The effectiveness has been limited in Nova Scotia and it may be because in many years the trees are not stressed during chemical thinner application.
    • This product can be used to increase fruit size (20g/fruit) beyond the influence of thinning by stimulating cell division but the timing matters. According to research:
      • When applied at 10-15 mm, it increases fruit weight 80% of the time.
      • When applied at 5 mm, it increases fruit weight 25% of the time.
      • When applied at petal fall, there is generally no increase in fruit size.

    Recommendations:

    • In a block that has trees that are on and off, thin according to the trees with the heaviest fruit set. You want to adequately thin the trees with heavy set and the trees with less set will be less likely to thin anyway (holding onto strong, well-supplied fruitlets).
    • If you have a usual rate that you use each year, then adjust it up or down by about 20% if you need more or less thinning activity.
    • If you need help determining how much crops should be left on trees, let me know and I can give you a thinning gauge.
    • Note that the PHI for Sevin is 75 days and this may be challenging for early varieties like Paula Red. The REI is 0.5-17 days depending on the activity.
    • Varieties prone to biennial bearing that had a low crop load last year should be thinned adequately and early enough this year to enable bud initiation (for Honeycrisp this is within 45 days after bloom). Thin to escape the biennial bearing cycle!

    Defruiting Young Trees

    • Defruiting young trees can be accomplished with a combination of Sevin XLR at 2.5 L plus Maxcel at 5.0 L per 1000 L of water applied using dilute nozzles to the point of drip. A few litres of oil (10.6 L/1000 L water) can also be added as a spreader sticker to this combination unless the variety is sensitive to oil. 
    • This mixture should cover more than an acre of young trees. Apply from petal fall until 8-10 mm. 
    • A second application can be done before 18 mm if additional thinning is needed. 
    • Hand thinning may still be needed.

    Pear Fruitlet Thinning

    • The Maxcel thinning window is 8-14 mm and early treatments are most effective.



    Horticulture



    Grafting

    • Bark is expected to be slipping.

    Mowing

    • Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.

    Pruning and Training

    • Prune newly planted trees to bring the top growth in balance with the root mass to avoid dieback from moisture stress.
    • Avoid aggressive pruning to avoid weakening trees. 
    • Ensure that deer fencing is installed as soon as possible to protect new growth on young trees.
    • Newly planted trees should be pruned for tree structure and supported as early as possible after planting. 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).

    Fertilizing

    • Urea may be used from pre-pink to mid-June as a nitrogen supplement. Sprays near bloom give a boost of nitrogen when it is needed most. Urea used from tight cluster to mid-July can remedy a nitrogen shortage.

    On-Farm Nursery

    • Monitor for tarnished plant bug and green aphids.
    • Remove rootstock leaves when they are tender and before shoots become woody. 
    • For bench grafts, leave some shoots on the rootstock to feed the scion as the callus tissue develops. Locally, rootstock leaves have been stripped when the scion has 8-10 leaves. Early in the season, leave at least an extra scion leader for insurance.
    • Consider staking soon to prevent blowouts. Even if not tied, the rod acts as a physical barrier to mechanical injury.
    • 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


    Funding Programs



    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: Joan Hebb, Jeff Franklin, Mathew Vankoughnett, Danny Davison, Ian Willick, Suzanne Blatt, Dustin MacLean, Vicky Levesque, Heather Rand, Bob Prange, Jeff Wentzell, Karen Burgher, Jill MacDonald, Larry Lutz, and Shawkat Ali.

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

    By Michelle Cortens at May 30, 2023
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