Orchard Outlook Newsletter Vol. 22, No 1

Tuesday, April 12, 2022


First Newsletter of 2022!

With an early snow melt it has felt like spring for a while and we're at the edge of our seat for the onset of growth. The Orchard Outlook Committee met virtually for the first time this season and we are happy to welcome new members to the table and to welcome back longstanding members for their input! Please see the list of committee members at the bottom of this newsletter. The annual Orchard Outlook newsletter will now be published every Tuesday on a regular weekly schedule during the main growing season.

Table of Contents:

  • Winter Weather Review
  • 2022 Degree Day Accumulations
  • Soil Temperatures
  • Cumulative Precipitation
  • Weather Stations in the Valley

  • Peach Bud Injury
  • Pear and Plum Cross Section
  • Updated Green Tip Estimate for Apple

  • Apple - Scab
  • Peach - Peach Leaf Curl
  • Japanese Plum Varieties - Plum Pockets
  • Plum - Black Knot
  • Pear Psylla



Winter Weather Review

The Environment Canada weather station in Kentville is used for comparison because historical data is available. The average monthly temperatures in Kentville were similar to or colder than the 5- and 10-year monthly averages (Figure 1).

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 observed this winter were colder than the 5- and 10-year averages in every month and especially in January when temperatures dipped below -20°C (Figure 2). Based on historical data, in any given winter Kentville has a 10% chance of observing temperatures below -20°C and Greenwood has a 16% chance.

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.

However, the Kentville weather station doesn't tell the full story! Critical cold temperature events were recorded on the local network of Davis weather stations in microclimates throughout the Valley on January 22 and February 2 (Figure 3)Extreme minimum temperatures were recorded that would be expected to damage buds and trees of some stone fruit crops. 

Critical winter temperatures expected to cause injury to flower buds include peach -23°C, cherry -26°C, plum -29°C and apple and pear -32°C to -34°C. Temperatures for tree damage include peach -25°C, sweet cherry -26°C, and apple -35°C. Tree and bud susceptibility may vary by 5°C depending on acclimation or deacclimation prior to the cold event. A discussion of bud injury is presented below in this newsletter's section on bud development.

Figure 3: Critical winter temperature events recorded on the NSFGA network of Davis weather stations on January 22 and February 2. Note the wide separation in temperatures throughout the Valley with the coldest temperature highlighted in purple and the warmest temperature in red.

2022 Degree Day Accumulations

This season we have observed above-average temperatures fairly consistently since the first week of March. Expectedly, the degree day accumulations are also above average but not quite as high as last year (Figure 4). For comparison, this year's degree day accumulations are on track with the year 2006.

Figure 4: 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 only a few warm events contribute significantly to the accumulated degree days.
  • Approximately 37% more plant development heat units compared to the 5-year average, and 34% more compared to the 10-year average.
  • Approximately 38% less plant development heat units compared to 2021, and 130% more compared with 2020.
  • Approximately 13% more insect development heat units compared to the 5-year average, and 2% less compared to the 10-year average.

Soil Temperatures

The soil temperature is relatively warm when compared to the previous 5 years (Figure 5). Limited frost in the ground this winter and snow melt by early March has contributed to the warm start in soil temperatures. Fumigation will begin when soil conditions are appropriate. Contact Danny Davison if you would like to request spring fumigation.
Figure 5: Soil temperatures at 35 cm depth at the Kentville Research Station from 2017 to 2022.

Cumulative Precipitation

Figure 6 is a graph of cumulative precipitation over the last ten years including rainfall and the rainfall equivalent from snow. Snowfall in January and February have made this year's cumulative precipitation the highest in the past 10 years, but precipitation has been close to average in March and April.
Figure 6: Both rainfall and the rainfall equivalent from snow at the Kentville Research Station from 2012 to 2021. Provided by Jeff Franklin (AAFC).

Weather Stations in the Valley

Last year, ten Davis weather stations owned by the Nova Scotia Fruit Growers Association were installed and they have been serviced for maintenance in the fall and spring through a contract with Perennia technical services. The maintenance has included updating firmware, changing batteries, levelling, and cleaning sensors. The 'North Medford (NSFGA)' station has a planned relocation to a more appropriate location in the orchard block to avoid clogging the rain gauge.

This year, Davis weather stations owned by individual farms that received provincial funding are being installed throughout the province. I cannot guarantee the accuracy of these stations, but they should serve as a useful resource if they are being maintained by the owner. All stations acquired with provincial funding are named with NSW in brackets and a station number. Many stations have already been installed this year and are publicly accessible on the Davis Weatherlink mobile app, including:
  • Billtown (NSW047)
  • Centreville (NSW010)
  • Gaspereau (NSW012)
  • Grafton (NSW042)
  • Grand Pre (NSW014)
  • Lower Canard (NSW015)
  • Melvern Square (NSW044)
  • North Medford (NSW041)
  • Paradise (NSW043)
  • Rockland (NSW033)
  • South Berwick (NSW034)
  • Starrs Point (NSW035)
  • Upper Canard (NSW016)
All Davis stations can be viewed on the free Davis Weatherlink mobile app. If you would like to create a custom list of weather stations to monitor on the app, download the Davis Weatherlink mobile app, create your own free private account then search for station names, and bookmark the stations to your list of favourites. 

NSFGA members have a shared account with preset stations and also paid access to the desktop weatherlink.com. However, if desired, NSFGA members can also create a free private account for the mobile app to add and re-arrange weather stations of their choice. Weather station owners were given their own private accounts.

Bud Development

Peach Bud Injury

Many regions exceeded critical winter temperatures for peach buds and, as a result, injury is being reported. Peach buds have a single flower in each flower bud and one flower bud is positioned on either side of a central vegetative bud. To evaluate for winter injury, the buds can be cut with a sharp razor blade. A living flower bud is green inside whereas brown tissue in the ovary at the base of the flower is an indication of winter injury (Figure 7). For comparison, a healthy peach bud is shown in an article from PennState.

Figure 7: Peach buds cut to show brown tissue indicative of winter injury. Two flower buds (F) are on either side of a central vegetative bud (V). (Left) Peach buds cut vertically; (centre) peach buds cut vertically, and (right) peach buds cut horizontally.

In the case of crop loss, trees would require less nitrogen for the season. Continue to maintain control of peach leaf curl, plum curculio, rot (at least with copper), and scab. Monitor and treat for mites and powdery mildew if they have been an issue.

Pear and Plum Cross Sections

Pear and plum critical winter temperatures were not exceeded and a limited number of cross sections suggest that the buds are healthy (Figure 8).

Figure 8: Buds cut to show healthy green tissue. (Left) Pear bud cut horizontally showing multiple healthy flowers in a single bud, and (right) plum bud cut vertically showing healthy flowers.

Updated Green Tip Estimate for Apple

According to Jeff Franklin's basic calculations on 12 years of generalized data, the average degree day requirement for bud break is 81.9 from January 1. A more in-depth explanation of this calculation was presented with the first green tip estimate posted on April 4, 2022

Based on updated weather information, the estimated first green tip date for early regions and early varieties is April 16, plus or minus 4 days. In any given year, the estimate from this simple model may deviate considerably so use it for guidance only. Regardless, it looks like time to prepare sprayers and clear brush from alleyways in anticipation of the first spray.


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. 
  • Watch for green tissue that would signal the need to apply a protectant fungicide 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.
  • If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.

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.

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. The fungicide Thiram is no longer registered so there are no options for chemical control. The only option is to 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. 


Pear Psylla

The first line of defence against pear psylla is the use of dormant oil to delay egg laying and synchronize control of pear psylla with later insecticide applications. Dormant oil application should be made as soon as possible when conditions allow.

Weed Management


  • With early snow melt comes the opportunity for early weed emergence! Look closely, the weeds are probably there. 
  • 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. 
  • If weeds are already present, add a post-emerge to a residual herbicide to achieve control.
  • If you have had trouble managing grasses, then it is important to treat them early for better control. 
  • Two new herbicides were registered in tree fruit this year. Prowl H2O, a pre-emergent for grass and broadleaf weeds on the label, and Assure II EC, a post-emergent for grassy weeds on the label.



  • 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. Prioritize high value trees and then return to low value areas.
  • 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 2022

The pest management guides are now available on our website for download. All changes new to 2022 are made in red text directly on the guides. The information on all expected changes was summarized in a blog post on April 8th.

Events and Notices

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

This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Colin Hirtle, Jeff Wentzell, Larry Lutz, Joan Hebb, Bob Prange, Dr. Suzanne Blatt, Danny Davison, Jeff Franklin, Dr. Ian Willick, Keith Fuller, Dr. Mathew Vankoughnett, and Dustin MacLean.

Edited by Michelle Cortens, Tree Fruit Specialist

Perennia Food and Agriculture Inc.

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