Orchard Outlook Newsletter Vol. 23, No 3

Tuesday, May 2, 2023

This week the newsletter focuses on early season disease management including recent apple scab infections and reminders about powdery mildew. There are observations about buds aborting on peach trees as a result of winter injury. The recent rain has been good for activating residual herbicides applied recently but Ignite should be avoided now until weeds are completely dry. Finally, there are a few reminders for folks planting trees. Thanks to the ongoing commitment of the Orchard Outlook Committee members.

Just a reminder that this week on May 3, I will be answering your frequently asked questions about fire blight during a webinar (see below). Everyone can benefit because the focus is on biology and understanding modelling practices.

Table of Contents:

  • 2023 Degree Day Accumulations
  • 2023 Soil Temperature
  • Apple Bud Growth
  • Peach Bud Update
  • Apple - Scab
  • Apple - Powdery Mildew
  • Apple - Fire Blight Prevention
  • Apple - European Red Mite

Weed Management

  • General
  • Pruning
  • Fertilizing
  • Liming
  • Planting
  • On-farm Nursery

Events and Notices

  • Perennia Webinar: Understanding Fire Blight Biology while using PomeBlight (pesticide points available)
  • Funding Programs
  • Pesticide Training Opportunities by Marbicon

Pest Management Guides 2023



2023 Degree Day Accumulations

Cumulative degree days are relatively similar to the 5- and 10-year averages for plant development (Figure 1). 

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 1 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 7% less plant development heat units compared to the 5-year average, and 1% less compared to the 10-year average.
  • Approximately 10% less plant development heat units compared to 2022, and 36% less compared with 2021.
  • Approximately 9% less insect development heat units compared to the 5-year average, and 9% less compared to the 10-year average.

2023 Soil Temperature

The soil temperature at 35 cm depth measuring 9.5°C is above-average when compared to the previous 10 years (Figure 4). Likely the warm soil temperature is attributed to less than average rainfall. Kentville recorded 45 mm of rain in for the month of April compared to a 25-year average of 83 mm. The current rain will cause some cooling this week.

Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2020 to 2023.

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 1, the Idared buds were at late 1/2 inch green, Honeycrisp was at 1/2 inch green and Ambrosia was at 1/4 inch green (Figure 2). Orchard Outlook committee members also report that varieties are at similar stages in Falmouth and Melvern Square.

Figure 3: Bud development in an early region on Middle Dyke Road in Kentville on May 1. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Peach Bud Update

In an earlier newsletter it was noted that there was winter injury damage to vegetative and fruit buds on peach trees. Recently the entire buds have begun aborting, including both vegetative and fruit buds. The wood on the shoot appears to be healthy. It appears that the barrier region between bud and shoot lost hardiness during warm January temperatures and succumbed to damage. Damaged buds could not be supplied with water and resources for further growth. We will continue to monitor how this influences management decisions.

Figure 4: State of peach buds on May 2, 2023. Photo submitted by Larry Lutz.


Apple – Scab

Table 1: Apple scab infection events in Kentville from April 25 to May 2, 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.


  • Over the last week, a lot of new tissue has been exposed and the current wetting event has brought significant rain. If copper was the main fungicide going into this long wetting spell with a lot of newly exposed tissue then protection could be questionable. Copper does not redistribute well. 
  • According to the forecast, ascospores are expected to mature at a rate of 1.5% per day and within the next five days about 20% of total seasonal ascospores are expected to be mature.
  • 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.
  • 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.
  • If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.
Figure 5: A lot of new tissue has been exposed over the last week. Take Honeycrisp for example from April 24 (left) to May 1 (right).

Apple – Powdery Mildew

Typically, conidia are released around the tight cluster stage. Powdery mildew infections can be expected when conditions are warm (10-25°C), humid and dry.


  • As opposed to scab, powdery mildew protection should be applied prior to a period of warm and dry weather when infections are expected. Do not apply a product for powdery mildew before a heavy rain is expected because:
    • The product will wash off.
    • Powdery mildew spores will not germinate on a wet leaf surface. 
    • Rain removes powdery mildew spores in the air and destroys spore-producing structures.
  • Application of a protectant mildew fungicide at tight cluster prevents primary infections of leaf clusters. Timely application early in the season will reduce the risk of secondary infections later. 
  • 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:
    • Powdery mildew: Group Ms do not have activity on powdery mildew so they will not help prevent powdery mildew resistance development. Products in the groups 3, 7 and 11 are registered for control of PM. Resistance to group 11 products was reported in a survey in 2013. Therefore, whenever the remaining 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

Typically the ooze begins to appear between tight cluster and early pink. Initially the ooze is a watery light tan that darkens to amber. When the canker blight bacteria are active, water sprout shoots close to cankers will wilt. 


  • 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.
  • Copper can be applied to nonbearing trees and processing varieties where fruit russet is not a concern.
  • When ooze is active, 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. 


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. Erika Bent, APM, reports that egg hatch has not yet begun in the Valley. 

European red mite eggs overwinter in the cracks on buds and spurs so adequate water volume is needed to reach all of the crevices. The oil treatment is not effective for rust mite or two-spotted spider mite.

Avoid oil if freezing temperatures will occur within 48 hrs and no captan within 7-14 days. Oil should not be applied to young trees at less than 3 years old, and the risk on varieties with Delicious parentage (Ambrosia, Gala) increases after tight cluster.

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.


  • The recent rain was good for activating residuals that had been applied in the last 7 to 14 days.
  • The recent rain means that Ignite should be avoided until leaf tissue has completely dried off on weeds. Applying Ignite when leaves are wet is ineffective and reportedly does not even burn leaf tips.
  • Applying 2,4-D in temperatures below 10°C has historically been ineffective. 
  • In young plantings, weed control is essential. Local research showed that by year 4, a weedy planting was 39% the trunk cross sectional area of a hoed comparison.



  • Remove tree guards because otherwise they can trap moisture and encourage disease. 


  • Plan ahead and watch re-entry intervals for pruning activities now that fungicide programs are ongoing. 
  • 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.
  • Target 10-16 inches of new growth each year. More is a sign of excessive nitrogen.
  • Foliar nutrients are not well-absorbed at below 10°C.


  • 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 (August) as pH can change over the growing season. 
  • The provincial limestone trucking assistance program is open.


Site and 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.

Nursery Tree Health
  • If growing your own trees, criticize their quality and don't plan to plant 100% of the trees. Planting small (<4 ft), weak trees will delay production. Trees are typically small for a reason and will continue to be weak trees. Commercial nurseries grade their trees and build in the cost of discarded trees so the same approach is recommended for on-farm nurseries. Tree losses of at least 10% are common.
  • Remember to document the quality of your nursery trees with pictures and notes. Did trees dry out? Any signs of disease (cankers, crown gall)? How do the roots look (rinse and take a photo)? Notify the appropriate people of issues you notice. Record the date of planting. An issue that shows up after planting is much easier to diagnose or prevent given this information.

Planting and Post-Planting
  • Avoid letting trees dry out. About 40% of trees can die from drying out, and surviving trees grow slowly. Survivors of 15-minute dry winds recover by year 3. Survivors of 45-minute drying winds still don't grow well by year 3.
  • Bundles of trees sitting in water awaiting planting can asphyxiate, especially in stagnant water and/or warmish water.
  • Trees should not be planted in waterlogged soil. Planting in heavy, wet soil can create a cemented layer around roots.
  • Pruning roots reduces growth in the first year, but roots can be pruned if they are damaged.
  • The worst conditions for apple replant disease are on light soils where poor root growth is combined with moisture stress. Install irrigation where possible.
  • The length of the rootstock that is above ground level will influence tree growth, Tree size diminishes as the rootstock portion above ground increases. Trees should be planted so that the graft unions are at a uniform height of 8 to 10 cm above the soil line.

On-Farm Nursery

  • Incorporate lime for nursery plantings rather than surface applications that will take years to take effect.
  • 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!
  • 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. 
  • Budded rootstock is being cut now or in the near future.

Events and Notices

Perennia Webinar: Understanding Fire Blight Biology while using PomeBlight (1 Pesticide Point)

On Wednesday, May 3 from 12 PM to 1 PM join Tree Fruit Specialist Michelle Cortens to learn about the biology of the disease while exploring scenarios through the modeling program. Explore questions like:
  • Where does bacteria grow and why?
  • When are flowers no longer at risk?
  • What is the role of water?
  • When exactly does bacteria grow?
  • How do I choose the first blossom date?
  • How do I know how much bacteria is present?
The ‘Understanding Fire Blight Biology while using PomeBlight’ webinar is NS Environment and Climate Change (ECC) course T2337 and is worth 1.0 point in Pest Management for continuing certification points.

Funding Programs

  • Please check the NSDA website for all programs under the Sustainable Agricultural Partnership: https://novascotia.ca/programs/. As this is a new 5-year agreement moving into the Sustainable Canadian Agricultural Partnership programs, producers will need to fill in a new Program Funding Registration Form
  • The Season Extension Enhancement program is meant to help support fruit and vegetable growers who invest in innovative technologies to extend their growing season, adapt to a changing climate and open up new market opportunities. For more information, visit Horticulture Nova Scotia

Pesticide Training Opportunities by Marbicon

Marbicon Inc (Jim Jotcham) has been announced Pesticide Training Opportunities. Pre-exam courses (with 5.0 points available for T2237):

Pre-exam courses (with 5.0 points available for T2237):
May 4 - Truro Horsemen’s Club in Bible Hill
May 23 - Berwick Legion in Berwick
June 8 - Truro Horsemen’s Club in Bible Hill

Points workshop (with 5.0 points available for T2236):
May 24 - Berwick Legion in Berwick
June 9 - Truro / Douglas Street Rec Centre, limited seating!
This workshop is not preparation for the provincial applicator exam.

Email/call Jim ( marbicon@eastlink.ca ) or 902-538-7101 to pre-register. Contact Jim if you would like a course near you and/or at a more convenient date. Pre-exam courses are $125 including HST.

People sitting in for 5.0 recertification points only pay $110 including HST.
Doors open at 8:30 am. Food & drink on your own. A course manual is provided.

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: Jeff Wentzell, Karen Burgher, Jeff Franklin, Larry Lutz, Ian Willick, Danny Davison, Crystal MacRae, and Shawkat Ali.

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

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