Orchard Outlook Newsletter Vol. 21, No 1

Tuesday, April 13, 2021


Table of Contents:

  • Winter Weather Review
  • 2021 Degree Day Accumulations
  • Soil Temperatures
  • Weather Stations in the Valley

  • Apple - Scab
  • Apple - Fire Blight Prevention
  • Peach - Peach Leaf Curl
  • Japanese Plum Varieties - Plum Pockets
  • Plum - Black Knot
  • Stone Fruit Varieties - Bacterial Spot
  • Cherry - Bacterial Canker


Weed Management

  • Pruning
  • Fertilizing
  • Liming

Pest Management Guides 2021

Events and Notices

First Newsletter of 2021

After a winter packed with endless options for virtual webinars, meetings, and conferences the time seems to have skipped forward to mid-April. It brings to mind a new word created during the pandemic called ‘blursday’. But even if every day feels like blursday, you’ll want to take note of Tuesdays when this newsletter will be delivered to your email inbox. Please note that the Tuesday release schedule is replacing the Wednesday schedule. The Orchard Outlook Committee met virtually for the first time this season so now newsletters will be released on a regular weekly schedule.



Winter Weather Review

The average monthly temperatures for December 2020 through to March 2021 are shown in Figure 1. The average daily temperature in December of +2.3°C was warmer than the 5- and 10-year monthly averages and average monthly temperatures continued to be similar to or warmer than the 5-year average.

Figure 1: Average monthly temperatures from December through March for the past three winters, and for 5- and 10-year averages at Kentville AAFC.

Extreme minimum monthly temperatures were also similar to or warmer than the previous 5- and 10-years. No extreme minimum temperatures were recorded in Kentville that would be expected to damage buds or trees.

Figure 2: Extreme minimum monthly temperatures from December through March for the past three winters, and for 5- and 10-year averages at Kentville AAFC.

2021 Degree Day Accumulations

With a warm start to spring this year the growing degree day accumulations are close to the highest they’ve been in recent years. For comparison, this year is on track with the years 2010 and 2012. Currently, development is ahead of schedule relative to the 5- and 10-year averages but it’s too early to tell if this trend will continue.

Figure 3: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to April 11th for the past 17 seasons. Provided by Jeff Franklin (AAFC).

For the following comparisons, please note that early in the season a few warm events contribute significantly to the accumulated degree days.
  • Approximately 146% more plant development heat units compared to the 5-year average, and 131% more compared to the 10-year average.
  • Approximately 279% more plant development heat units compared to 2020, and 166% more compared with 2019.
  • Approximately 231% more insect development heat units compared to the 5-year average, and 176% more compared to the 10-year average.

Soil Temperatures

The soil temperatures are currently the warmest they have been at this time in recent years. Limited frost in the ground this winter has contributed to the warm start in soil temperatures. Fumigation will begin when soil conditions are appropriate. If you haven’t already, contact Danny Davison to request fumigation.

Figure 4: Soil temperatures at 35 cm depth at the Kentville Research Station from 2016 to 2021.

Weather Stations in the Valley

The Nova Scotia Fruit Growers’ Association through federal and provincial funding with the Nova Scotia Department of Agriculture has embarked on a project to install and maintain weather stations. Perennia representatives have been involved in this project in an advisory and collaborator role along with many other folks in the industry. As you might have seen in the most recent NSFGA newsletter, stations are in the process of being coordinated and installed. Three of the ten weather stations are already operational. Please stay tuned for a presentation on how to access the weather data. The live weather data will be accessible in several formats, for example it is on a quick ‘weather’ tab on the NS Tree Fruit Blog.

Bud Development

Overview: The early heat has translated into some green tissue peeking through bud scales, although bud progress has slowed in the cool weather over the last few days. It’s time to prepare sprayers and clear brush from alleyways in anticipation of the first spray.

Early region: In an early region on Middle Dyke Road in the Kentville area, the majority of the Idared buds are showing green tip. Honeycrisp has green tips showing but relatively fewer. The bud scales on Ambrosia are just beginning to separate. Early regions have green tissue on Gingergold and Gravenstein as well.

Figure 5: Bud development in an early region on Middle Dyke Road in Kentville. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Other regions: In North Medford, Gravenstein and Idared are showing green tissue on many but not all buds. In the South Mountain area, Sunrise is at green tip but generally the Jonagold, Honeycrisp, and McIntosh are not yet.

Forecast: The warming expected on this coming Thursday, April 15th is expected to encourage more growth so keep an eye on the development stage. 


Apple – Scab

Beginning at green tip, apple tissues are susceptible to infection from the fungus that causes apple scab, Venturia inaequalis. The environmental conditions for an infection are listed in the Modified Mills Table. Primary infections are caused by ascospores present in the leaf litter and infections develop on spur leaves, terminal shoots, and young fruitlets. Ascospore maturity is aligned with bud development so that mature spores are ready to be released when buds show green tissue. If not controlled, primary infections will create spores that generate secondary infections for the rest of the season. The best approach to fruit protection is to control primary scab.


  • If bud development is not yet at the green tip stage, it is not at risk of apple scab infection.
  • A period of rainfall is currently forecast for Saturday, April 17th. With the currently forecast temperatures of a high of +4°C and a low of +2°C, it would take around 37-41 hours of leaf wetness for an apple scab infection event to occur, according to the Modified Mills Table.
  • Note the potential for green tissue growth to appear in next week’s warmer weather. Apply a protectant fungicide to green tissue prior to the first infection event and reapply on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
  • Vigilant protection of primary scab will prevent the challenges that come with chasing secondary scab. Secondary scab will be increasingly challenging with upcoming product discontinuations.
  • Always tank mix single site fungicides with a group M for resistance management.
  • Early in the season, there is no need to control powdery mildew so products with activity on powdery mildew can be saved for application at half inch green.
  • If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.
  • Note that the new captan containing product Maestro 80 WSP has re-entry periods that differ depending on the orchard density and activity (anywhere from 2-24 days).

Apple – Fire Blight Prevention

The goal of copper application is to cover the bark with copper to reduce the population of bacteria on plant surfaces that arise from bacterial ooze around the pink stage. The copper treatment will reduce the initial inoculum and limit the spread of fire blight bacteria to blossoms or wounded tissue on the tree. This strategy is most effective in blocks that had fire blight cankers in the previous two seasons.


  • A copper application is recommended when buds have reached green tip. A fixed copper product such as Copper Spray Fungicide (50% copper oxychloride) is recommended because it is resistant to being washed off by rain. Cumulative rainfall of 100 mm will wash away most of the product, which is why it is applied no earlier than green tip. If applied later than green tip, residues that persist on fruitlets can cause russetting.
  • Copper can be applied as a tank mix with 0.5% by volume (5 L in 1000 L) dormant oil to increase adherence. Apply in a high water volume to cover plant surfaces. Do not use dormant oil within 14 days of Captan or within 48 hours of freezing temperature. A half rate of an EBDC can be included as extra protection for apple scab.

Peach – Peach Leaf Curl

Peach leaf curl is a disease caused by the fungus, Taphrina deformans, which causes deformation and premature leaf drop of peach and nectarine leaves. If trees are left untreated, the fungal disease can reduce yield, fruit quality, and lower overall tree health. The spores of Taphrina deformans overwinter on the bark of the tree and when buds swell the spores are washed into the bud where they infect young tissues.


  • A protectant fungicide is needed in spring if one was not applied in fall, or if you applied a fall fungicide but disease pressure is generally high. The fungicide can be applied when buds are dormant and up until bud swell. Delayed applications prior to green tip will still provide some but not complete control.
  • If applying a fungicide during both fall and spring, do not repeat the use of chlorothalonil products (Bravo ZN or Echo 90 WSP) because they can be applied only once for peach leaf curl either as a fall or spring dormant spray.
  • Chlorothalonil products have worked best in Nova Scotia. Alternatives are listed in the spray guide.
  • Bravo 500 will be discontinued. The last day for growers to apply these products is May 10, 2021. Review new label requirements for Bravo ZN related to mixing, loading and application.

Japanese Plum Varieties – Plum Pockets

This fungal disease is caused by Taphrina communis. Infection causes the fruit to become large and deflated. The fungus travels by spores soon after bud break.


  • Thiram is the only product registered for control and it is applied just prior to bud swell. If applied later, Thiram will still provide some but not complete control.
  • Thiram is still a registered use according to label directions. However, the regulatory decision was to cancel uses of Thiram on apple, peach, and plum. Product is being phased-out and the last date of use is Dec 14, 2021. 
  • Plant disease-resistant varieties.

Plum – Black Knot


  • Prune out black knot infections by cutting at least 8 inches below the knot. Pruning is the primary way to control this disease.
  • Knots should be burned immediately. Do not dispose near your orchard because spores will travel back to the orchard. 

Stone Fruit Varieties – Bacterial Spot


  • Cueva is the only product registered for use. Use a 0.5% to 2% solution, applied at 470-940L/ha. Re-apply using 5-10 day intervals. Apply as a dormant spray as buds begin to swell, repeating at the bud burst stage, and weekly thereafter as needed, up to five sprays for peaches and 10 for nectarines.
  • Plant disease-resistant varieties.

Cherry – Bacterial Canker


Copper products listed in the spray guide can be used prior to bud break to suppress bacterial canker (Pseudomonas syrinage) in sweet and sour cherry. This treatment should be made prior to bud swell to avoid phytotoxicity.


If mice damage has been an issue, consider the risk of tree suckers. Suckers have thin bark, so they are an easy food source that attract and feed mice.


  • Pay particular attention to young trees that are most susceptible to damage. 
  • Remember that bait is available and registered to help with rodent management. 
  • The issue of rodents is aggravated if weed management is poor and the ground cover creates a habitat for them to hide.

Weed Management

In 2020, the Nova Scotia Department of Agriculture conducted a detailed survey of the weeds in 37 orchard blocks. The top 10 weeds arranged by relative abundance are shown in the figure. Of those weeds, the willowherb is concerning in the sense that roundup is not very effective if applied too late. Early control with 2,4-D and Roundup are most effective otherwise they can escape management. Lontrel is effective on vetch and clovers. Chateau and Devrinol are good on groundsel.


  • Studies have shown maintaining weed free strips from bud break to 30-days after full bloom has the greatest impact on tree growth and yield. Timely herbicide application will ensure you make the most of the weed free window. 
  • Residual herbicides such as Chateau, Alion, and others offer a much longer weed control period than post-emergent products such as Ignite, Gramoxone, and Glyphosate. Chateau should not be applied after budbreak unless application equipment is shielded to prevent crop injury. Always follow label directions. Note that residual herbicides can damage single tree replacements. 
  • Weeds are emerging. If weeds are already present, consider adding a post-emerge to a residual herbicide to achieve control.



  • If pruning is delayed, plan a strategy to get the most value for your time. Prioritize young blocks and high value varieties and return to low value areas. This strategy is especially important considering the new captan limitations.
  • With bud break just around the corner, ensure that youngest blocks are pruned first to ensure growth is directed into desirable leader and terminal extension. 
  • Mature blocks can be pruned later and are best when pruned prior to bloom.


  • Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth.


  • Lime especially if a site is being planted this year. When applied in spring the lime works best when applied as soon as possible to get the product working in the top layer of soil. 
  • Surface applied lime will take a number of years to adjust pH of the soil profile so it is best to apply annually or biannually where needed. If soil testing for pH, measure during the same time each year as pH can change over the growing season. 
  • The provincial limestone trucking assistance program is open.

Pest Management Guides 2021

The pest management guides will be posted on our website soon. The information on all expected changes was summarized in a blog post on April 9th

Events and Notices

For upcoming events, visit the ‘Events’ tab on the NS Tree Fruit Blog. Specific events will be described here when available.

Edited by Michelle Cortens, Tree Fruit Specialist

Perennia Food and Agriculture Inc.

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