Orchard Outlook Newsletter Vol 22, No 17

Tuesday, November 8, 2022

Today's newsletter is the final issue for Volume 22 in the year 2022. In the last issue of the season I review a summary of tree health, crop load, pest pressures and fruit quality that can be easy to refer to in the future. It's hard to believe we're already well into November given the warm temperatures we've been experiencing but this is also an opportunity for winterizing orchards and getting ahead of disease control. Cheers to you all for wrapping up another harvest season! 

Table of Contents:

  • Weather
  • Tree Health
  • Crop Load
  • Notable Pest Pressure
  • Harvest and Fruit Quality
  • Conclusion
  • Fall herbicide application
  • Fall soil pH adjustments
  • Orchard rodent control
  • Reducing the risk of apple scab
  • Peach leaf curl
  • Workshops and conferences for the winter season

2022 Season Summary


Degree day accumulations and development were above-average this past growing season. Harvest finished earlier than average.

Figure 2: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to Oct 31st for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 5% more plant development heat units compared to the 5-year average, and 5% more compared to the 10-year average.
  • Approximately the same plant development heat units compared to 2020, and 4% more compared with 2019.
  • Approximately 6% more insect development heat units compared to the 5-year average, and 5% more compared to the 10-year average.

Tree Health

Extreme winter temperatures in January 2022 resulted in several types of injury. Regions exceeded critical winter temperatures that killed peach and cherry buds. After trees expended energy during bloom, damaged apple trees started to collapse and the injury became apparent. Gravenstein and Northern Spy trees showed the most damage. Also, weakened trees and fall-pruned trees were at greatest risk of injury. Injured trees attracted borers that aggravate the problem. Southwest injury to the trunk also occurred and can be confused for cankers.

Crop Load

Freezing temperatures were recorded on May 8 and 9 when apple buds were at the tight cluster stage of development. Minor frost injury occurred and king buds were most prone to injury. Apple trees started bloom relatively early by around May 14. The bloom was fairly compacted and pollination conditions were good with sunny days, moderate temperatures, and bee activity. 

Early in the chemical thinning window, the moderate daytime temperatures and cool nighttime temperatures created difficult-to-thin conditions. Later in the window, daytime temperatures warmed to ideal conditions for thinning activity. Therefore, thinning conditions were typical of Nova Scotia conditions unlike the heat waves of the recent past. Nearing harvest it became clear that the overall crop load was above-average.

Notable Pest Pressure

Above-average temperatures in early spring led to early maturing ascospores and wetting periods produced infection events that occurred roughly every week. This season a total of 9 primary infection events were recorded, which is slightly less than has been typical in recent years. The event on May 15/16 was notable because it released up to 40% of total spore load.

Fire blight showed up frequently this year where protection was inadequate. There were several infection periods during a critical period of bloom throughout the Valley. Most regions were at risk of blossom blight infections on May 22 and on May 29/30. The risk continued for new plantings that bloomed during the summer heat. Trauma blight events were recorded from isolated hail on June 18, and after wind from post-tropical storm Fiona on Sept 24.

Also this year, adjusting spray programs to the new restrictions on captan continue to be challenging. Getting work done in the orchard involves balancing reasonable costs, REIs, and PHIs. Next year will present the new challenge of working with the amended label for manzate (mancozeb) that restricts the number of applications to 4 per year and an REI for hand thinning of 35 days.

A more detailed review of diseases was described in the August 31 newsletter.

Harvest and Fruit Quality

Early in the season, temperatures were conducive to red colour development. Then colour development seemed to stall, possibly related to warmer temperatures or stress from post-tropical storm Fiona. In some cases, using ReTain delayed colour development by too much, especially under heavy crop load. More growers are experimenting with leaf removal and pneumatic defoliators.

An extended period of dry weather in June and heavy crop loads limited the size of Gala fruit.

On Sept 24, post-tropical storm Fiona resulted in crop loss that varied depending on the orchard location and variety. High winds also led to trellis failure in high crop load situations and occasional tree collapse. Some fruit were rendered unmarketable by cuts and bruises. Also, bitter pit continues to be a widespread observation.


Overall, the industry has a good crop but some crop loss and structural damage occurred during hurricane Fiona.

Winterizing Orchards

Fall Herbicide Application

Fall is prime germination time for winter annuals, and perennials are susceptible to treatment because they’re actively storing reserves in their roots. Refer to last year's special article 'Fall Weed Control for Winter Annuals and Pesky Perennials' for more information. We've had a good period of time this fall with warm and dry weather to apply herbicides.

Key points:

  • Summer and winter annual species have populations that germinate in both fall and spring and therefore troublesome weeds may need to be managed at both times.
  • After harvest, consider using a post-emerge herbicide to clean up weeds along with a residual product to save time early next season. Orchards without fall application of residual herbicides are expected to exceed weed thresholds in early spring before those treated with residuals.
  • If planning to apply glyphosate, wait until late spring to avoid translocation to fruit tree root systems.
  • Even if you are not set up to perform weed control in the fall, now is a good opportunity to identify what weed species are present to inform herbicide choices for early next year.

Fall Soil pH Adjustments

Soils in the valley are naturally acidic, and nitrogen fertilizers will slowly acidify soils over time. As soils acidify, nutrients such as calcium, potassium and phosphorus are less available for uptake by fruit trees. Other nutrients such as manganese and aluminum become more available and uptake by fruit trees can become excessive.

The pH of orchard soil should be between 5.5 and 6.6 (target 6.0) because nutrient availability is best within this range. Fall is the ideal time to make soil pH adjustments because it gives time for limestone to neutralize the acidity before the next growing season. Also in the fall, the dust from limestone applications will not interfere with growth or bloom.


  • The results of a soil test will give a lime requirement based on your soil type and pH.
  • Apply calcitic limestome unless magnesium is needed from dolomitic limestone.
  • A surface application of no more than 3 tonnes/ha of limestone in any one year is recommended because higher volumes could be washed away and are ineffective.
  • If the lime is being worked into soil then you can follow the recommended rate on your soil report. Incorporating lime into soil will show benefits sooner than a surface application. A surface application moves down at a rate of about 1 inch per year.
  • If you have ongoing issues with lack of calcium in established plantings, consider banding gypsum at a rate of 4 tons per acre under trees. Annual applications have been shown to reduce bitter pit and senescent breakdown. Gypsum can also improve soil structure and improve water infiltration. Be aware that gypsum can reduce magnesium uptake. Gypsum will not replace the need for lime for pH adjustment.

Orchard Rodent Control

Rodents feed on tree bark in the fall and winter when other food supplies are scarce. The most common issue is when rodent feeding girdles the trunk of young trees at or near the ground surface or at the height of snow accumulation.


  • Mow ground cover and maintain a weed-free strip to expose mice to predators.
  • Clean up drop apples from the tree row and alleyways to remove attractive food sources.
  • Be aware that using straw mulch can harbour mice.
  • If rodent activity is observed (mouse tunnels, droppings and chewed apples), consider the use of rodenticide. Bait stations manage the risk of poisoning other species and the control is long-lasting.
  • Bait stations placed on the perimeter of the orchard target mice moving into the orchard from bordering fields, fence lines or ditches. Pay particular attention to orchard blocks that neighbour corn and soybean fields.
  • Install tree guards, if feasible, on young trees. Remove after snow melt in spring to avoid fungal problems at the base of the trunks.


Reducing the Risk of Apple Scab

Scab spores can be reduced for the next growing season by accelerating the decay of infected leaves in the fall of the current season. The benefit is less disease pressure next spring that can help to reduce the risk of primary scab infections. All efforts to reduce primary inoculum for next year will be helpful for scab control under new fungicide restrictions.


  • Spraying urea (46-0-0) onto leaves on the ground can reduce spores by about 66%. The recommended rate is 50 kg/ha in 1000 L/ha of water. The solution could alternatively have been applied to full trees as leaf fall began. Urea should be dissolved in warm water before putting it in the tank. The 50 kg/ha rate will supply approximately 23 kg/ha of nitrogen to the ground, so nitrogen application next spring should be adjusted accordingly.
  • Flail chopping all plant matter on the orchard floor in November can reduce the number of scab spores by as much as 85%. Flail chopping in only the alleyway can reduce scab spores by as much as 50%. Why does chopping work? Dr. Gordon Braun explained in a year 2000 publication that:
    • "By chopping up leaves finely, they are more easily broken down by bacteria and molds to be consumed by earthworms."
    • "The apple scab fungus needs to mate with the opposite mating type and smaller leaf pieces reduces the likelihood of the two meeting."
    • "The smaller fragments also fall deeper into the grass and have a greater probability of resting in a position which is less than horizontal which reduces the ability of the ascosopres being successfully discharged into the air currents and carried to susceptible leaves."
  • Using both shredding and urea applications can produce the best results.

Peach Leaf Curl

Peach leaf curl is a fungal disease of peaches and nectarines that is usually well-controlled by a fungicide application in spring or late fall. Infections occur in the spring at bud swell when overwintering spores are washed from the surfaces of the bark. Therefore, a fungicide application prior to bud swell in the spring is preferred. However, occasionally early warm temperatures combined with extended snow cover can make spring applications challenging.


  • The spores overwinter on the bark, so fall applications for peach leaf curl should be tailored to provide complete coverage of trunks and branches. Fall application should be made after 75-100% of leaf drop has occurred and when the temperature is above freezing.
  • Unusually wet winter weather with heavy rain can wash off a protectant fungicide applied in fall. If residues are washed off, re-treatment in spring before buds swell is recommended. 
  • Chlorothalonil (Bravo) has been the most effective fungicide in Nova Scotia. Only 1 spray of Bravo may be applied per year, meaning it cannot be applied in both spring and fall. Other products registered for control include fixed copper products and Syllit.

Events and Notices

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

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