Orchard Outlook Newsletter Vol. 24, No 2

Tuesday, April 23, 2024

Today's newsletter focuses on early season disease management including the season's first apple scab infection event and considerations for fire blight sanitation. We review horticulture practices including notching for blind wood, reminders for planting, and resources on planning windbreaks. Thanks to the ongoing commitment of the Orchard Outlook Committee members.

Table of Contents:

  • 2024 Degree Day Accumulations
  • Cumulative Precipitation
  • Apple Buds
  • Pear and Stone Fruit Buds
  • Apple - Scab
  • Fire Blight Sanitation
  • European Red Mite

Weed Management

  • Pre-emergence Residual Herbicides
  • Post-emergence Herbicides
  • Notching for Blind Wood
  • Pruning
  • Fertilizing
  • Liming
  • On-farm Nursery
  • Land Preparation
  • Windbreaks

Events and Notices

  • Resilient Agriculture Landscape Program

Online Pest Management Guide



2024 Degree Day Accumulations

Over the last week there have been slow gains in degree days. The degree day accumulations beginning on March 1 are still slightly ahead of the 5- and 10-year averages (Figure 1).
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to April 22 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 9% more plant development heat units compared to the 5-year average, and 25% more compared to the 10-year average.
  • Approximately 26% more plant development heat units compared to 2023, and 2% less compared with 2022.
  • Approximately 3% less insect development heat units compared to the 5-year average, and 9% more compared to the 10-year average.

Cumulative Precipitation

Figure 2 is a graph of cumulative precipitation over the last five years including rainfall and the rainfall equivalent from snow. Rainfall contributed to most of this year's cumulative precipitation. Jeff Franklin shares that, "The cumulative precipitation plot shows that we are currently above the 10-year trend and that most of our precipitation has come in March and early April with some significant single day rainfall events. It also shows data from 2019, when we received our precipitation in smaller more frequent events. The data from 2019 shows that we had rain on 40 days in the months of April and May!"
Figure 2: Both rainfall and the rainfall equivalent from snow at the Kentville Research Station from 2019 to 2024. Provided by Jeff Franklin (AAFC).

Bud Development

Apple Buds

An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on April 22, the Idared buds were at quarter-inch green, Honeycrisp was at green tip and Ambrosia was at green tip (Figure 3). Orchard Outlook committee members report that apple varieties in Kentville and Falmouth also range from green tip to quarter-inch green. Growth appears to be 2-days ahead of last year.

Freezing temperatures as low as -5.5°C were recorded early this morning in apple growing areas. No direct injury to buds is expected. The potential for spring frost/freeze injury depends on the stage of development. The critical temperatures for bud injury in degrees Celsius can be accessed in this chart from Perennia for your reference.

Figure 3: Bud development in an early region on Middle Dyke Road in Kentville on April 22. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Pear and Stone Fruit Buds

Yesterday on April 22 at an early region in Greenwich, the pear buds were at swollen bud, peach was at quarter-inch green, and European plum was at bud burst (Figure 4). Orchard Outlook committee members also report that pear in Kentville is at swollen bud. Sweet cherry in Kentville is at the swollen bud stage.

Figure 4: Bud development in an early region in Greenwich on April 22. Shown from left to right: pear, peach, and European plum.


Apple – Scab

Table 1: Apple scab infection events in Kentville from April 16 to April 23, based on the Modified Mills Table. 
1 For a high inoculum orchard, a significant number of spores can be released during darkness, so begin calculating leaf wetting regardless of the time of day when the wetting event started. An orchard is considered to have a high inoculum load if last season it had 100 or more scabby leaves observed over 600 shoots.
2 Assuming a green tip date of Saturday, April 15th. Please use this as a guide because microclimates will cause conditions to vary on individual farms.
Note: The environmental conditions for an infection are listed in the Modified Mills Table.

The Avonport-Falmouth area received heavy rain on Sunday around 5 PM. The leaves were dry for a short period of time on Sunday until they were re-wetted and therefore the two wetting periods would be combined (Sat 18 hrs + Sun 18 hrs) to equal 36 hrs of leaf wetness. The affected areas would have observed a moderate infection event.


  • Currently there is no rain in the forecast but do not let it lure you into a false sense of safety because precipitation forecasts can change quickly. There has been more tissue exposed and spores are maturing so orchards should receive regular fungicide protection. According to the forecast, ascospores are expected to mature at a rate of 0.5% per day and within the next five days about 4% ascospores are expected to mature and be available for release.
  • Apply a protectant fungicide to green tissue prior to an infection event and reapply on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
  • 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.
  • Remember that Manzate (mancozeb) products 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.
  • If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.

Fire Blight Sanitation

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. 


  • Please note that tissue injury could occur when copper is used alone or combined with oil when hard frosts/freezing temperatures occur, such as those temperatures currently forecast for the next few nights.
  • A copper application is recommended when buds are at the green tip stage. A fixed copper product such as Copper Spray Fungicide (50% copper oxychloride) is recommended because it is resistant to being washed off by rain. If applied later than green tip, residues that persist on fruitlets can cause russetting which is a concern for fresh fruit varieties. Processing varieties where russet is tolerable can be treated later as well as nonbearing trees.
  • 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. 
  • Cankers are visible now before they become hidden by this year's foliage. Scout for cankers now.
  • If in doubt, take it out! No cankers are helpful and they harbour diseases. If you need a second opinion, I can take a look. Cankers are especially risky in young orchards because they harbour the bacteria for new blossom infections that give bacteria rapid access to the leader of the tree. Consider completely removing young trees that have cankers.


When green tissue is present, do not use dormant oil 48 hours before or after freezing temperature. Oil that is applied before freezing temperatures breaks down and adheres to the plant tissues unevenly instead of the target insects. Also if the oil and water mixture freezes before it dries then the green tissue can be injured. Please note that there is the risk of freezing temperatures in the forecast.

European Red Mite

A delayed dormant oil is effective at managing European red mite if monitoring indicates a treatable overwintering egg population. The oil is most effective when applied around egg hatch (typically around tight cluster and before pink) but if practical it may be applied earlier with less effective results. European red mite eggs overwinter in the cracks on buds and spurs so high water volume is needed to reach all of the crevices. The oil treatment is not effective for rust mite or two-spotted spider mite.

For varieties with Delicious parentage (Ambrosia, Gala, Delicious), early applications of oil prior to tight cluster are less likely to result in bark blistering. Oil should NOT be applied to young trees.

Weed Management

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.


Pre-emergence Residual Herbicides
  • Most residual herbicides need about 1/2" of rainfall within 7 to 14 days of application to deliver product to the germination zone and to activate the chemical by putting it in solution. 
  • Note the differences in the application directions for Chateau and Alion and refer to the labels for more detailed information:
    • Chateau can be applied to young trees. Chateau should not be applied after budbreak unless application equipment is shielded to prevent crop injury. 
    • Alion can be applied only to mature orchards with trees established for 3 growing seasons. Alion can be applied anytime throughout the growing season.
    • Note that residual herbicides can damage single tree replacements. The Alion label says that individual plants within an orchard may be replanted by removing all treated soil from the transplant hole and refilling with soil that has not been treated.
    • If you are taking out orchard within the next 2-3 years for replanting, avoid applying residual herbicides. The Alion label says to allow at least 12 months from last application to replanting an orchard.
  • Chateau and Authority are good products but they do not have a lot of grass control so rotate with other products to avoid shifting toward more grass population. Chateau may be tank mixed with Prowl H2O to widen the weed spectrum for selective control of annual grasses and extend control.
  • When mixing residual herbicides, agitation is important to keep the product in solution. If the herbicide settles in the tank then it can be delivered in a high concentration and possibly result in crop injury.
  • If weeds are already present, add a post-emerge to a residual herbicide to achieve control. 

Post-Emergence Herbicides 
  • Treat early at the 3-6 leaf stage for optimum weed control. Young leaves have a less well-developed cuticle and absorb more. Crop damage is also minimized.
  • Post emergence herbicides are best applied on warm and sunny days. Glyphosate and 2,4-D require daytime highs of 10°C-15°C after a night above 3°C to have good activity.
  • Applying Ignite when leaves are wet is relatively ineffective.
  • In the USA, there are concerns about Ignite causing bark cracking. The specific risks are yet to be defined but just be cautious that Ignite is not sprayed onto or drifts onto young tree bark.
  • Venture takes about 3 weeks to kill labelled annual and perennial grasses. Growth ceases immediately but the death is slow. Don't use Ignite with Venture because Ignite will burn top growth before Venture kills it. If grasses become tall you may use Ignite to burn the grass down and then during grassy regrowth apply Venture to kill systemically. Wait at least 3 days after Venture before applying an herbicide for broadleaves.
  • Perennial weeds may be targeted in spring when new perennial plants are at the seedling stage. Other timings are spot sprays at the early flowering stage or during fall re-growth after a minor frost. Glyphosate and group 4 products are systemic and work on certain perennial plants.


Notching for Blind Wood

  • Notching and applying plant growth regulators (Promalin and MaxCel) is best done from green tip and up until bloom time. The ideal time is at the stage of half-inch green.
  • Please note that the success rate of inducing a branch depends on the age of the planting. Applying a mist of plant growth regulators to the notched area can increase the success rate, namely for older plantings of up to 7 years of age.
  • Notching is preferred over scoring. Scoring can oftentimes heal over and you lose the effect.
  • The plant growth regulators work in cooler temperatures but warm temperatures at the time of application increase the response. For more information, see an article by MSU Extension.
Figure 5: Notching trees above a paradormant bud removes the cambium and disrupts the flow of auxin. Doing so allows the buds to break dormancy.


  • Plan ahead and watch re-entry intervals for pruning activities when fungicide programs begin. 
  • Ensure that youngest blocks are pruned first so growth is directed into desirable leader and terminal extension. Prioritize high value trees and then return to low value areas. Consider prioritizing pruning in fire blight blocks to finish prior to tight cluster when cankers begin oozing.
  • Pruning may be delayed for vigorous Ambrosia to reduce its vigour.
  • Mature blocks can be pruned later and are best when pruned prior to bloom.
  • A handout for farm workers 'The Fundamentals of Pruning' was published this year.


  • Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth. 
  • If leaf and soil samples show that phosphorus and potassium are adequate there is no need to apply phosphorus and potash. Granular formulations with 0.3 boron are encouraged for sandy soils.
  • If Honeycrisp is on the rootstock G.41 then potassium additions are discouraged.
  • Target 10-16 inches of new growth each year. More growth is a sign of excessive nitrogen.


  • Lime soils prior to planting an orchard with rates according to your soil report. Early spring is an option but fall can be a more practical time to apply lime to a new site and lengthen the time for acidity to become neutralized.
  • Orchard maintenance with surface applied lime twill 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 (August) as pH can change over the growing season. 
  • The provincial limestone trucking assistance program is open.

On-Farm Nursery

  • Rootstocks that were chip or t-budded last year may have buds pushing. Cutting rootstock tops early can help to prevent the rootstock from overpowering the new buds. Rods may also be put into place early to avoid knocking off buds if done at a later timing.
  • Early application of granular fertilizer can minimize the risk of leaf burn. Otherwise, granules can get trapped and sit in new leaf tissue that is close to ground level. 

Land Preparation

  • Wet conditions are a great opportunity for marking wet spots in the field to repair tile drainage. 
  • Remember the importance of soil preparation. Remove old roots and work to get a good soil tilth without sods and clods especially in the top 15 cm of soil.
  • When trees are first planted they need a high level of soil phosphorus because roots are too poorly developed to forage for it. If phosphate is needed, diammonium phosphate (DAP) can be banded in furrow. There is no need to apply phosphorus if a soil test shows P2O5 to be high, such as on land with a history of manure application.


Events and Notices

Resilient Agricultural Landscape Program

The Resilient Agricultural Landscape Program helps to improve the environmental resiliency of agricultural landscapes by accelerating the adoption of on-farm land use and management practices that maximize benefits for the environment and society. Buffers and shelterbelts are listed in the program guidelines for 100% of the establishment costs up to $1,500/acre for creating or widening buffers. The maximum assistance is on a case-by-case basis. For more details, visit the NSDA Program page.

Online Pest Management Guide

Beginning this year, all of the pest management guides are now available from an online tool. On the tool you will find guides for organic and conventional apples, pears, peaches/nectarines, plums, and sour/sweet cherries. You can search and filter the information and/or print. To help you navigate the guide, we have developed a brief tutorial video as well as a how to use guide.

The apple and pear guide have been fully reviewed. The stone fruit guides are currently under review. I will post the growth regulator guide soon. This year is a transition year as Perennia has migrated all of the information to a new format and this tool will continue to improve as we actively work on it. Please stay tuned.

This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Larry Lutz, Jill MacDonald, Suzanne Blatt, Ian Willick, Danny Davison, Jeff Franklin, Dustin MacLean, Mathew Vankoughnett, Harrison Wright, and Shawkat Ali.

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

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