Orchard Outlook Newsletter Vol. 23, No 5

Tuesday, May 16, 2023

This week the newsletter discusses dry weather conditions with implications for management and programs to access for improved infrastructure. In terms of diseases, you should be on alert for early blossoms opening to determine your fire blight infection risk. Currently, the EIP risk is low in cool temperatures but the situation can change quickly and industry alerts will be provided to email subscribers although the use of PomeBlight is encouraged. There is now a new resource available, it is a pre-bloom insecticide decision table to help you compare products for your unique insect complex. We also review the blossom thinning strategy and note that winter injury observed to some king buds can complicate thinning. Thanks to the ongoing commitment of the Orchard Outlook Committee members.

Table of Contents:

  • 2023 Degree Day Accumulations
  • 2023 Soil Temperature
  • 2023 Precipitation
  • Apple Bud Growth
  • Apple - Scab
  • Apple - Powdery Mildew
  • Apple - Fire Blight Prevention
  • Apple - Fire Blight Blossom Blight
  • Fire Blight - Shoot Blight Management
  • Apple - Calyx/Blossom End Rot (Advance Notice)
  • Apple - Black Rot (Advance Notice)
  • Nematodes
  • Pre-Bloom Insecticides

Blossom Thinning

  • Weed Management
  • General
  • Pollination
  • Grafting
  • Mowing
  • Pruning
  • Fertilizing
  • Liming
  • On-farm Nursery

Events and Notices

  • Funding Programs
  • Pesticide Training Opportunities by Marbicon

Pest Management Guides 2023



2023 Degree Day Accumulations

Cumulative degree days continue to be slightly behind the 5- and 10-year averages for plant and insect 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 15 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 8% less plant development heat units compared to the 5-year average, and 10% less compared to the 10-year average.
  • Approximately 18% less plant development heat units compared to 2022, and 24% less compared with 2021.
  • Approximately 10% less insect development heat units compared to the 5-year average, and 18% less compared to the 10-year average.

2023 Soil Temperature

The soil temperature at 35 cm depth is relatively close to average at 11°C (Figure 2).

Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2020 to 2023. Provided by Jeff Franklin (AAFC).

2023 Precipitation

Currently in the first half of May, the Kentville weather station has recorded 20 mm of rain out of the monthly average of 74 mm. Note that although the total precipitation this year intersects with the average, the slope of the line in spring of 2023 has been relatively horizontal because of little accumulation of precipitation (Figure 3).

Figure 5: Both rainfall and the rainfall equivalent from snow at the Kentville Research Station from 2020 to 2023. Provided by Jeff Franklin (AAFC).

According to the Canadian Drought Monitor report posted April 30, 2023, areas of the Annapolis Valley were classified as abnormally dry to moderate drought (Figure 4) and have received 40 to 60% of the average precipitation. Certainly, perennial crops like tree fruit are at less risk of moisture fluctuations than annual crops. There is still an opportunity for this dry trend to change. 

However, keep an eye on drought susceptible soils and young plantings to irrigate where possible. Check out OMAFRA's article with example calculations for scheduling drip irrigation (high-density apple tree crop coefficient is 1.0). Also, it is likely that granular fertilizer is being released slowly. Note that nematodes may also cause more severe damage in drought conditions.

There are currently some very good programs available to cost-share your improvements to water resources. 
Please check the program guidelines for specific details and contact NSDA Programs for more details.

Figure 4: Classifications from the Canadian Drought Monitor as of April 30, 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 15, the Idared buds were at the pink stage, Honeycrisp was at bud separation and Ambrosia was at early bud separation (Figure 5). Orchard Outlook committee members also report that varieties are at similar stages in Falmouth, Morristown, and Melvern Square. Plus, in the western Valley some king blossoms are beginning to open on Gala and Gravenstein. Pear is nearing bloom.

Figure 5: Bud growth in an early region on Middle Dyke Road in Kentville on May 15. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Some damage to king buds is being realized a result of winter injury (Figure 6). The king bud was furthest along in development by the time of extremely cold winter temperatures and appeared to be more susceptible than lateral buds. It is recommended that you check varieties prior to chemical thinning to evaluate the extent of king bud injury.

Figure 6: Damaged king buds observed on May 12 and 15. Shown from left to right: Idared, Idared, Minneiska.

Turning our focus to terminal shoots, they will soon begin to elongate (Figure 7, left). Apogee/Kudos can be applied beginning at 2.5 cm of shoot growth so the application period is nearing. 
In situations of heavy crop load last year, biennial bearing varieties like Honeycrisp may be on their off-year and producing few fruiting buds (Figure 7, right).

Figure 7: Honeycrisp vegetative bud growth on May 15. Terminal shoots will soon elongate (left). Biennial bearing varieties may be in their off-year (right) following heavy crop load last year.


Apple – Scab

Table 1: Apple scab infection events in Kentville from May 10 to May 16, 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.


  • According to the forecast, ascospores are expected to mature at a rate of 3% per day and within the next five days about 67% of total seasonal ascospores are expected to be mature.
  • We continue to be in a very high risk period. The next apple scab infection will have a significant spore load available. 
  • Apply a protectant fungicide to green tissue prior to an infection event on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth. Otherwise, waiting for rain is a gamble with the hopes that protection is applied in time (and the possibility of relying on post-infection treatment).
  • Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
  • 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.
  • Alternatives to Manzate for resistance management? Captan may be applied if it is not 7-14 days within an oil. Allegro may be applied 1 day after an oil.

Apple – Powdery Mildew

Powdery mildew infections can be expected when conditions are warm (10-25°C), humid and dry.


  • Powdery mildew protection should be applied prior to a period of warm and dry weather when infections are expected.
  • When using Nova, the water soluble packaging should not be mixed with oil or boron. 
  • Apply two sprays targeting powdery mildew prior to bloom on the re-application schedule noted on the product being used (usually 7-14 days).
  • 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


  • Isolated hail was reported on May 13 at 10:30 PM near Melvern Square and Grafton. A fire blight trauma alert was sent by email to subscribers. If hail created wounds then trees are at risk of trauma infection by bacteria from overwintering cankers. Warm temperatures are not a requirement for trauma blight.
  • 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. 
  • If interested in pinching buds on young trees the practice can begin around the bud separation stage when it's possible to avoid removing the terminal shoot. Pinching buds becomes risky as bloom begins because fire blight bacteria grow on the flower stigma and are expected to be present in high numbers in warm weather. Do not pinch flowers when tissues are wet. This practice is time-consuming and any remaining flowers are susceptible to infection.

Apple – Fire Blight Blossom Blight

Fire Blight Biology
Open blossoms must be present for a blossom blight risk. Fire blight bacteria are transported from overwintering canker sites to open flowers by the action of insects and rain. These bacteria then reproduce on the stigma of flowers and are washed down into the base of the flower by a wetting event – a minimum of just 0.25 mm of rain or heavy dew – which then initiates an infection if adequate bacterial populations are present. An average daily temperature of at least 15.6°C is needed to establish infections and the infection potential rises with consecutive hours above 18.3°C. Blossom blight risk increases with warm temperatures between 23°C and 27°C, especially when occurring over consecutive days because this temperature range is ideal for bacterial reproduction. The Maryblyt model criteria is used to predict blossom blight infections.

Monitoring Regions for Blossom Blight Alerts
This year, all NSFGA-owned weather stations will be used for industry alerts. Those weather stations are located in the following communities: Atlanta, Aylesford, Grafton, Grand Pre, Melvern Square, Morristown, Moschelle, North Medford, Windsor, and Woodville.
  • Short notice blossom blight alerts will be delivered directly to your email inbox. Periods with high fire blight bacterial populations are defined by Maryblyt as having an Epiphytic Infection Potential (EIP) greater than 100. Notifications will be sent as soon as it is evident that the EIP will approach 100 for apples and pears. 
  • If you would like to join the alert contact list, please let me know at mcortens@perennia.ca or sign up online. Alerts will be delivered on weekends and holidays.
  • Ideally you will monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers. Contact me if you need a quick refresher or need help setting up. Run the model using your own temperature, rainfall, bloom and spray dates (industry alerts will offer limited scenarios). 

Current and Forecast Blossom Blight Risk
  • Please watch for and take note of your first blossom date.
  • For very early flowers that are currently beginning to open, the EIP value for apples and pears is currently low. 
  • According to the forecast, the EIP will remain low into the near future indicating that an infection is unlikely in the next few days. 
  • Stay tuned because predictions can change on short notice.


  • Streptomycin 17 will provide excellent efficacy on blossom blight and is best used up to 24 hours prior to an infection event. If necessary, it may be used after infection and is best used within 20-24 hours. It is recommended that you keep Strep on the farm at this time of year to respond quickly. Streptomycin 17 may be used up to 3 times each year.
  • Kasumin also has excellent efficacy and may be used up to 4 times each year during bloom. Consider using Kasumin if you need to re-enter a block because it has a short REI of 12 hours. However, the PHI for Kasumin is 90 days, which can be challenging for early varieties like Paula Red. Note that Kasumin is not partially systemic and should not be used for post-infection control or after a trauma event.
  • For on-farm nurseries, consider applying a copper product at the lowest labeled rate prior to training trees and follow the labeled REI. Make cuts on only dry and sunny days.

Fire Blight - Shoot Blight Management


  • Apogee/Kudos (prohexadione calcium) supress shoot blight. The timing of the first application at 2.5-7.5 cm of new shoot growth is critical to success. Follow up with a second application applied around 14 days later.
  • Apogee should be put on with higher water volumes to cover all new leaves and growing tips.
  • Include Agral 90 at 500 mL per 1000 L of water. Do not exceed this amount of surfactant. 
  • If applying Agral 90 there may be a risk of burn if using Captan.
  • Apogee should also be applied with spray grade ammonium sulphate (AMS) in an equal 1:1 ratio with the amount of Apogee used (e.g. 500 g Apogee = 500 g or 0.5 L of ammonium sulphate). This is not the blossom thinning product ammonium thiosulphate (ATS)!

Apple  Calyx/Blossom End Rot (Advance Notice)

The disease is caused by the organism Sclerotinia sclerotiorum. Infections develop when conditions are warm (15 to 25°C) and moist during and shortly after bloom. The infection originates on sepals or dying petals and spreads to the calyx end of the fruit. The disease is most common on Paulared, Delicious, Cortland, Honeycrisp and McIntosh.

Symptoms appear about one month after petal fall on the calyx end of the fruit as a brown/grey discolouration that later develops a red border. The lesion is usually sunken and a corky dry rot develops in the flesh. When in storage, calyx end rot can lead to moldy core. 

The disease should not be confused with dry eye rot that is caused by Botrytis cineria from an infection that occurs later in the season. If you typically see symptoms, contact me if you would like to confirm the organism through lab testing.


  • If calyx/blossom end rot has been an issue in the past, consider using a captan product during full bloom. Infections can occur in problem blocks as the pathogen can last in the soil for several years.
  • If applying Streptomycin with Agral 90 there is a risk of burn if using captan. Prioritize fire blight over blossom end rot.
  • Keeping grass and dandelions mowed will allow the soil to dry and reduce the environmental conditions for spore ejection. Other broadleaf weeds are also a host of this disease so weed control prevents the build up of this pathogen.

Apple – Black Rot (Advance Notice)

Although early, I think this is a good time to consider how to reduce the risk of black rot. Last year we heard from Dr. David Rosenberger and the following suggestions from him might be helpful to consider:
  • Black rot can survive on prunings. Flail mow prunings in row middles where they will degrade more quickly.
Minimize lenticel cracking by:
  • Avoiding drought stress with irrigation
  • Being cautious with spray mixtures (folpet, calcium, foliar nutrients). Be especially cautious when heavy rains follow drought conditions because rapid fruit expansion can break lenticels and allow product to cause more damage than usual, making it susceptible to fungal infection.
  • The black rot fungus infects fruit during warm rains from petal fall to harvest: A 10 hr wetting period at 16°C to 32°C allows infection. 



Root and soil samples are best collected in the spring (May-June) or during the fall (September-October), both of which avoid the heat or drought conditions in summer. Soil temperatures at sampling should be above 10°C for adequate nematode presence in the upper soil levels. Samples can be processed by the Agriculture and Food Laboratory (AFL) in Guelph, ON.

Note from Perennia's Plant Pathologist, Dustin MacLean regarding dry soils: 
Dry soils may provide a favourable environment for nematodes, as plant parasitic nematodes gravitate towards root tissue while any predatory organisms retreat deeper into the soil in search of water, as well as the plant being weakened, allowing for infection to more easily occur. 

Additionally, damage caused by nematodes in drought years is often more severe than when water is abundant. Nematodes may also exacerbate the impact from other root and stem diseases by weakening the plant and providing wound openings for other pathogenic organisms to invade. Like many of the root and stem diseases mentioned previously, damage caused by nematodes is often mistaken for water stress and premature senescence and may benefit from the discerning eye of a specialist to identify the cause.

Pre-Bloom Insecticides

Depending on the heat in the forecast, your region, and monitoring reports, action may be needed soon during the pink stage.

pre-bloom insecticide decision table has now been created for Nova Scotia (Table 2). Use this resource to choose pre-bloom insecticides according to the pest complex on your scouting report. Take note of the higher rate required for some pests. You may begin by determining the product and rate for your most difficult to control pest and then note the other pests that will be managed by your product selection.

Table 2: A list of insecticide products and labelled pests for apple is now available. 

Spring Caterpillar Complex

(winter moth, green pug moth, eyespotted bud moth, speckled green fruitworm, obliquebanded leafroller)


  • Evidence of feeding includes tiny holes in new leaves and flower buds, and black specks of frass. Begin scouting procedures described in Perennia’s Best Management Practices. Monitor your scouting reports for notes on WM, GPM, and other caterpillars for those with scouting services.
  • Note that there is a lower tolerance for WM than GPM. Green Pug Moth do not feed directly on developing fruitlets.

European Apple Sawfly


  • Last year there were high catches of EAS in the Valley.
  • In orchards with a history of damage and high numbers of EAS catches, an application of a registered insecticide at full pink is recommended to control the adults prior to egg laying.

Tarnished Plant Bug


  • If history of tarnished plant bug damage indicates that pressure is moderate to high, an application of insecticide at pink is warranted. Treatment should be applied before bloom, not after.

General Notes

  • Monitor for rosy apple aphid populations that exceed thresholds when aphid stem mothers start producing offspring. Treatment pre-bloom is ideal. Closer works well for aphid control.
  • As a reminder, pyrethroids are best used at moderate temperatures (20°C or less) and lose efficacy at around 25°C. They are harsh on beneficial insects and predator mites. They should only be used where potential losses justify their application.

Blossom Thinning

The caustic thinner ammonium thiosulphate (ATS) is the first chemical thinning opportunity of the growing season. ATS reduces pollen germination, interfering with fertilization. 

  • May lead to increased fruit size and return bloom compared to later fruitlet thinning. ATS could be a good consideration for early thinning of small fruited varieties (e.g. Ambrosia and Gala). 
  • The caustic activity of ATS does not depend on the temperature at application, unlike fruitlet thinners.

  • This year there was frost injury to king buds. This is a complication because blossom thinning attempts to thin after the king bud is set to target killing side buds. Without a king bud, the differentiation between side buds is challenging.
  • Beware that if the fire blight risk is high (infection pending a wetting event) an antibiotic is needed prior to ATS or wait until the risk has decreased.
  • You are thinning with an unknown crop load (before fertilization). 
  • There is potential for foliar spray injury. If ATS is applied to dry leaves then there is less chance of injury. Some foliar and petal burn is normal and suggests the concentration is effective for thinning. 
  • It can increase fruit russet so avoid sensitive varieties as a precaution.
  • Blossom thinning cannot compensate for a lack of bud removal during pruning.


  • ATS can be applied towards the later part of full bloom (80-100% FB), at which point adequate pollination of king flowers has occurred. Do not wait much longer and especially don't wait until petal fall because it can be too late.
  • The goal is to apply ATS when the king flower has had enough time to become fertilized but prior to the lateral flowers becoming fertilized. For more accurate timing, consider that in order to become fertilized, a pollen grain must germinate on the stigma and grow a pollen tube to the base of the style to reach the ovary. In cool temperatures of 13°C, fertilization of open flowers takes 5 days and in warm temperatures of 24°C, fertilization takes 2.5 days. Therefore, time the ATS application for several days after the desired percentage of bloom has opened.
  • In Nova Scotia, ATS has been used at 5.5 L in 100 gal/acre (13.6 L ATS in 935 L/ha). The concentration is what matters for its activity so don’t concentrate it by spraying a lower volume. Keep records to learn from your results. If you are not familiar with the product, be conservative with the rates, use it on a small area first, and talk to someone with experience about rates.


Weed Management

  • This week may be a good opportunity for burndown herbicides if needed. If you have not yet acted, act soon because full control is already unlikely as weeds are becoming large.
  • 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.


  • If you plan to have tile drainage installed in the near future, talk to your drainage company early because they are booking far in advance. 
  • Remove tree guards because otherwise they can trap moisture and encourage disease. 


  • Consider that it is near the time that honeybees should be moved into the orchard for pollination when king flowers open.
  • Bees can become accustomed to wild sources of nectar and may ignore apple blossoms. Mow dandelions to encourage apple blossom foraging. 


  • Bark typically slips from pink to bloom.


  • Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of pre-bloom insecticide applications.


  • Plan ahead and watch re-entry intervals for pruning activities.
  • 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 are best when pruned prior to bloom to avoid weakening trees.


  • Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth.
  • Foliar nutrients to correct nutrient deficiencies:
    • Boron: Applied pre-pink. Do not use water soluble pesticide bags in a tank mix with boron and rinse the tank well before and after boron. Do not use boron with oil or Epsom salts.
    • Magnesium: Epsom salts are applied starting at pink. Do not use with oil or boron.
    • Nitrogen: Urea may be used from pre-pink to mid-June as a nitrogen supplement. Sprays near bloom give a boost of nitrogen when it is needed most. Urea used from tight cluster to mid-July can remedy a nitrogen shortage.
    • When foliar nutrients are applied in slow drying conditions, about 40% is absorbed in 6 hours. When applied in dry conditions, about 75% can be lost in 48 hours. 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.

On-Farm Nursery

  • Monitor for tarnished plant bug and green aphids.
  • Consider staking soon to prevent blowouts. Even if not tied, the rod acts as a physical barrier to mechanical injury.
  • 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!

Events and Notices

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

The next series of in-person courses from Marbicon Inc (Jim Jotcham) are confirmed.
This may be the final courses offered until October/November this fall.
They will need a minimum of 8 people for any additional courses this spring.

Pre-exam courses (with 5.0 points available for T2237):
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 points workshop is not preparation for the provincial applicator exam.

Email/call Jim ( marbicon@eastlink.ca ) or 902-538-7101 to pre-register.

Pre-exam courses are $125 including HST.
People only sitting in for 5.0 recertification points pay $110 including HST.
Doors open at 8:30am. Pay at the door. Cash, cheque, or e-Transfers only. No credit/debit cards.
Food & drink on your own.
A course manual is provided for pre-exam courses. Bring a pen.

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: Bob Prange, Dustin MacLean, Joan Hebb, Jeff Wentzell, Crystal MacRae, Suzanne Blatt, Mathew Vankoughnett, Karen Burgher, Keith Fuller, Jeff Franklin, Jill MacDonald, Shawkat Ali, Vicky Levesque, and Larry Lutz.

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

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