Orchard Outlook Newsletter Vol 21, No 11

Tuesday, June 22, 2021


Table of Contents:

  • 2021 Degree Day Accumulations

  • Apple - Scab
  • Apple - Powdery Mildew
  • Fire Blight - Orchard Management
  • Apple - Black Rot/Frog-Eye Leaf Spot
  • Apple - Brooks Spot
  • Apple - Flyspeck and Sooty Blotch
  • Stone Fruit - Brown Rot, peach scab, and powdery mildew

  • Apple Insects (Leafhopper, aphids, codling moth, mites, leaf roller, apple maggot)
  • Pear Insects (Psylla, rust mite, codling moth)

  • Solstice Reminders
  • Pruning and Training
  • Young Trees
  • Calcium Nutrition
  • Weed Management
  • Nursery Trees
  • Mowing
Pest Management Guides 2021

Events and Notices
  • Perennia & NSDA Weather Station Survey
  • Bitter rot and apple scab samples for AAFC
  • Perennia has moved to downtown Kentville!



2021 Degree Day Accumulations

The above-average trend continues with total degree day accumulations similar to 2006, 2010, and 2012.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to June 21st for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 19% more plant development heat units compared to the 5-year average, and 16% more compared to the 10-year average.
  • Approximately 22% more plant development heat units compared to 2020, and 33% more compared with 2019.
  • Approximately 26% more insect development heat units compared to the 5-year average, and 22% more compared to the 10-year average.


Apple – Scab

An infection event was ongoing at the time of the previous newsletter. That same infection is now posted below as the only primary infection for the previous week.

Table 1: Apple scab infection events at the Kentville Research Station from June 15th to June 21st, 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 Tuesday, April 14th. Please use this as a guide because microclimates will cause conditions to vary on individual farms.
3 All forecasts are estimates. Observe forecasts daily for more accurate predictions.
Note: The environmental conditions for an infection are listed in the Modified Mills Table.


  • On the June 15th heavy infection event, the remaining 0.7% of total seasonal spore load was released. The Modified Mills table predicts that lesions will appear within 12 days of this infection event.
  • On June 8th the ascospore maturity model predicted 100% ascospore maturity was reached. Dr. Sajid Rehman analyzed a sample from Morristown taken on Monday, June 21st. Based on the small sample, there are no more viable and mature ascospores in the leaf litter for future wetting events. Also, this year's above average temperatures suggest that ascospores have had the required heat to mature by this point in time.


  • Do not reduce fungicide spray intervals until you can identify your pressure from secondary scab lesions. Also note the risk of summer diseases if spray programs are stretched to the limit.
  • Where primary lesions are present, secondary infections have been occurring and will continue during wetting events of sufficient duration. The minimum wetting required for secondary infections is 3 hours less than the wetting required for primary infections.
  • The pre-harvest interval for EBDC fungicides (e.g. Manzate, Dithane, Polyram) for fruit destined for the United States is 77 days versus 45 days for the domestic market. An application of EBDC on June 22nd would require until September 7th to meet pre-harvest requirements for the United States.
  • Always tank mix single site fungicides with a group M for resistance management.
  • Polyram has now been phased-out due to the cancellation of the active ingredient. The last date of use has passed on June 21, 2021.
  • Be careful mixing water soluble packaging (WSP) with other products. Do not use WSP in a tank mix with boron and rinse the tank well before and after boron.
  • 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 to 24 days).

Apple – Powdery Mildew


  • Powdery mildew pressure is high this year. On young trees, monitor for active mildew to determine the need to protect new terminal growth. Only group 3, 7, and 11 fungicides have activity and resistance is a concern in group 11. This issue of not having enough groups is widespread across apple growing regions.
  • Remember that late summer sprays are protectants and not eradicants. Flag shoot symptoms from overwintering infections will be visible for the rest of the season.
  • Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.

Fire Blight - Orchard Management


  • Continue to monitor for signs of fire blight blossom infections, especially in young blocks.
  • In blocks with historically high pressure, prune only when the forecast calls for at least 2 days of sunny, dry weather. As an extra precaution, disinfect tools after working in a block with fire blight pressure.
  • When pruning, remove fire blight strikes at least 2-4 ft below active infections to remove the leading edge of the bacteria. Being aggressive at the first sign of symptoms will help prevent the re-occurrence of symptoms and the need for continuous cutting back. Leave prunings in orchard alleyways to dry thoroughly for several weeks. 
  • Monitor for shoot blight on suckers that can infect the rootstock.
  • 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.

Apple - Black Rot/Frog-Eye Leaf Spot

This disease has been an issue in certain orchard blocks. Varieties most prone to infection include Honeycrisp, Northern Spy, Delicious, Sunrise, and Ginger Gold.

Figure 2: The black rot fungus is commonly found in mummified apples (left) and dead bark. The black rot conidia were found in mummified apples in May 2021 and work is ongoing. Photo by Dr. Sajid Rehman (right).

  • The heaviest spore release is believed to occur for a four to six week period following petal fall. If considering when to apply the second and final Captan on a low-density block, we are currently in the assumed high risk period and rainfall would release spores.
  • Infection can develop on fruit after about a 9-hour wetness period at an average temperature around 20-24C.
  • Fungicides are protectants because they prevent spore germination on plant tissues so for protection from this disease the fungicides would need to be applied prior to the wetting event. 
  • Do not reduce rates of Captan after bloom in high density orchards that have a history of black rot. Consider this recommendation where practical in terms of new label restrictions. Pristine and Merivon would also have good protective activity.
  • Check for nearby brush or wood piles because they serve as a major source of inoculum. Remove the brush pile to reduce the chance of infection.
  • This year on regular samples volunteered by Joan with Scotian Gold we are exploring how to monitor for black rot inoculum. The process that we define this year will help us monitor the spore profile in more detail next year. With this disease, conidia are supposedly active as early as silver tip and ascospores are active in the period between petal fall and 4 to 6 weeks later.

Apple - Brooks Spot

Brooks spot is caused by a fungus that creates sunken, dark green lesions on the fruit. It is a minor disease that has been an issue on Honeycrisp in the past. The symptoms of Brooks Spot can resemble lenticel breakdown and bitter pit which are also common on Honeycrisp. Include a product for cover sprays that is labelled for brooks spot such as Inspire Super and Aprovia Top.

Apple - Flyspeck and Sooty Blotch

These summer diseases develop on the surface of the fruit in midsummer until harvest. They are caused by fungi that overwinter in dead twigs and the fungi tend to cause more infections under conditions of moderate temperature, high humidity and rainfall. Include a product for cover sprays that is labelled for flyspeck and sooty blotch such as Captan, Maestro, Inspire Super, Aprovia Top, Allegro, Pristine, and Merivon.

Stone Fruit – Brown Rot, Peach Scab, and Powdery Mildew


  • Fungicide protection from brown rot should be maintained during periods of warm, wet weather. 
  • The new formulation of Captan limits the number of applications to one per year on stone fruit.
  • Peaches are susceptible to peach scab infections from shuck fall to 4-6 weeks before harvest. Symptoms are visible on the bark. The shuck fall application is particularly important for disease control. Periods of wet weather will require additional applications until 4-6 weeks before harvest.
  • Monitor for signs of powdery mildew on fruit and refer to the Stone Fruit Management Guide.


Apple Insects

  • White apple leafhopper: Monitor for white apple leafhopper. Sevin XLR applications on mature blocks will control leafhopper but monitor non-bearing plants for leafhopper. If treatment is required, a neonicotinoid, Sivanto Prime, or Exirel would control leafhopper and also pick up aphids.

  • Aphids: Monitor for rosy apple aphid and green aphid. In young trees the aphids can disrupt shoot growth. Monitor nursery plantings as well. Now that leaves are curling high water volumes are needed for effectiveness. Green aphid will move back into orchards that were treated previously so continue to monitor. Assail and Calypso also have activity on codling moth, apple maggot and leafhoppers. Be cognizant of REIs if installing trellis.

  • Codling moth: The biofix dates for this season are June 3rd and 4th for early regions and June 6th for later regions determined by Erika Bent, APM. Jeff Franklin, AAFC, ran the degree day model to predict degree day thresholds for treatments. The models were run again on Monday, June 21st with a degree day threshold of 10 degrees (C). The models are run using Kentville temperatures for predictions and actual timing may vary based on observed temperatures throughout the Valley.


    • The treatment timing for egg hatch products has been met for early and late biofix dates. 
    • The treatment timing for organophosphate (Imidan) is slightly later at 140-degree days after biofix. Based on current forecasts, the projected treatment date for regions with a June 6th biofix date is June 23rd. The treatment timing has been met for earlier biofix dates.
    • If trap captures are below the treatment threshold but continue to build over time then treatment should be applied once a threshold is reached. 


    • These are approximate dates and if you applied a treatment just before or after these dates you should still have acceptable control, especially if trap captures were relatively low. 
    • Codling moth lay eggs and hatch over a period of time. Late application may miss the first egg hatch and could result in a few codling moth entries. 
    • A heavy rain just after application is more concerning than a late application because it would wash off and reduce the residual life of the insecticide. 
    • Approximately a week after application of an OP insecticide, clean out the trap and start monitoring the trap. The capture of an additional 10 or more moths would indicate that a second treatment is required.

  • Mites: European red mite, two spotted spider mite and apple rust mite are the prominent species that affect apple trees. Although not directly damaging to the fruit, these mites in all their motile life stages can drain the nutrients from the trees and dramatically degrade fruit quality.
    • Scout your orchards or check your scouting reports to see if there is a treatable population.
    • Both European red mite and two-spotted spider mite are controlled by the products Acramite, Apollo, Kanemite, and Nealta. All three mite species are controlled by Nexter and Envidor.
    • Mites have many generations per year and therefore have a high potential to develop resistance. For resistance management, it is critical to rotate miticide classes. The use of dormant oil applications will also help to delay resistance selection for European Red Mite.

  • Obliquebanded leafroller: Adults will take flight to lay eggs for the second generation. Monitor or check scouting reports for larval populations soon.

  • Apple Maggot: In 2012 that had similar heat to this year, the first capture of apple maggot in a heavily infested orchard was reported on June 29th. Captures in commercial orchards were more common around July 10th. In blocks that are still being treated for codling moth, the control is extended to early maggot flies. No captures have been noted yet for this year but Dr. Suzanne Blatt at the research station will be putting out traps before the end of June.
    • The economic threshold is 1 maggot fly per orchard on a yellow sticky board. Apply a treatment 7-10 days after the first fly is captured on a yellow sticky board or immediately after a female is captured on a red sphere.

Pear Insects

  • Pear psylla: Refer to the management guide for product options.
  • Pear rust mite: Can go unnoticed until heavy russeting extending from the base to the top of the fruit. Growers that apply Agri-mek for pear psylla control would also obtain pear rust mite control. Nexter or Envidor would be other options for pear rust mite control.
  • Codling moth: Refer to the above degree day timing given for apples.


Solstice Reminders

  • If granular fertilizer is applied now, the risk is that any dry weather in July will slow the release. Late release will prevent trees from hardening off before the winter. Top dressing is not recommended after the end of June.
  • Around July the trees are storing reserves in the roots for next year’s growth. When they are storing reserves, late glyphosate applications can be damaging if taken up by root suckers and transported to the root system. Avoid the risk by avoiding glyphosate applications after the end of June.

Pruning and Training

  • If bamboo is limited because of COVID delays, we recommend looking at other options in the meantime. As young trees grow more foliage they are more susceptible to sailing in the wind. Consider running wire supports or new solutions to support trees. The hurricane season has begun and even the risk of high wind events is cause for concern.
  • Prioritize trees that are known to be brittle at the union, including many of the new Geneva rootstocks (G.11, G.41, G.16 etc).
  • Train and support young trees as soon as possible. Remove competing terminals. Work in dry weather especially if the block has historically high risk of fire blight.

Young Trees

  • Broadcasting grass seed is not recommended for establishing grass in the alleyway. Direct seeding is recommended to confine the grass seed to the alleyway and avoid spread to the tree row. The herbicide gramoxone used to provide good control of bluegrass species but post-emerge products for grass control are now limited.
  • Ensure that deer fencing is installed as soon as possible to protect new growth on young trees. Deer are browsing young plantings and causing damage. Thiram is no longer an option to deter feeding while the fence is being installed. Another deterrent product called Bobbex is available for nonbearing trees.
  • Remove root suckers. Suckers compete with the main tree for water and nutrients. They harbour pests, and they are an entry point for fire blight. Pull or break off suckers because otherwise cutting them would let them rebound. If necessary, AIM herbicide is registered for control of suckers but avoid drift onto young trees and apply only near mature brown bark.

Calcium Nutrition

  • The goal of Ca sprays is to increase the concentration of Ca in the fruit and reduce bitter bit incidence. 
  • Calcium applied at two-week intervals is better than occasional, high-rate applications. 
  • The recommended rate is 4 to 14 pounds of elemental calcium per acre in a season spread over six to eight cover sprays. The percentage of elemental calcium will be listed on the label.
  • Ca has very low movement within the tree and needs to be applied directly to the fruit surface to be absorbed. Therefore, thorough coverage is important to cover developing fruit.
  • Calcium chloride flake (77% Ca) is the most economical Ca material to use but also the highest risk for foliar burn. Apply calcium chloride flake at no more than 4.5 kg per 1000 L of spray solution. The risk of leaf or fruit damage from calcium is highest in hot and dry weather. Susceptible varieties can develop lenticel spotting if damaged. 
  • Risk of leaf injury may be enhanced by Captan. Incompatibility has been observed with Epsom salts, and liquid or emulsifiable pesticide formulations in some cases. Do not apply calcium with apogee.

Weed Management

  • Note that 2,4-D has an 80-day PHI. Eighty days from now is September 10th. 
  • Remember the importance of weed control in nurseries and young plantings. Management practices now will impact the outcome of the final tree. Encourage the growing point to be successful.

Nursery Trees

  • Scion leaders will need support.
  • Aim is registered for nurseries but it is a hot product and caution is recommended around green tissue. The product is not volatile but green tissue is very sensitive on contact.
  • Monitor for aphids, leafhoppers, and tarnished plant bug.
  • Strip the lower leaves on nursery rootstock before they become woody.


  • As grass becomes long the extra surface area increases transpiration. Keep grass mowed to conserve moisture.
  • Keeping the orchard floor cover mowed will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.

Pest Management Guides 2021

The pest management guides are available online for download. All changes new to 2021 are made in red text.

Events and Notices

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

Perennia & NSDA Weather Station Survey

Perennia and the Nova Scotia Department of Agriculture understand the vital role having access to real-time weather data and weather models for producers in making proactive crop management decisions. This is even more important given the severe weather episodes of the past several years and the changing climate.

We have begun discussions on how we can support you in this area. Your responses will help them tailor programs, tools and resources that serve you and your needs in this area. No unique responses are linked to respondents so please feel safe being free in sharing. The survey should take no more than five minutes.
Deadline to complete and submit is June 22, 2021.

Bitter Rot and Apple Scab Samples for AAFC

The Plant Pathology Lab of Kentville’s Agriculture and Agri-Food Canada is looking for apple growers who will participate in a province-wide study of the fungal pathogens responsible for bitter rot and apple scab disease in apple. One of the goals of the research is to look at the fungicide resistance profile to find out which fungicides are still effective or not. This is an industry and AAFC funded project. 

Growers who notice either bitter rot or apple scab appearing in their orchard are invited to contact Dr. Shawkat Ali (shawkat.ali@canada.ca) or Shayne McLaughlin (mc615708@dal.ca). Researchers will then monitor the orchard to collect diseased leaves or fruit from the orchard for further study. Samples cannot be collected from the orchard floor due to rapid deterioration. The industry needs your help in identifying sites where samples can be taken.

Perennia office has moved to downtown Kentville!

We are now located at 28 Aberdeen Street in downtown Kentville. Our office phone number stays the same: (902) 678-7722. Please note, we are not open for visitors until July 5th. You can access the building from Aberdeen Street and walk through to the back parking lot where our entrance is or enter the back parking lot (turn left beside the Independent grocery store off Webster Street) where we have designated parking and our own separate entrance. For those of you familiar with Kentville over the years, we are in the old Access Nova Scotia space.

This Orchard Outlook has been published with the input of the Orchard Outlook Committee
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Inc.

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