Orchard Outlook Newsletter Vol 21, No 4

Tuesday, May 4, 2021


Table of Contents:

  • 2021 Degree Day Accumulations
  • More Weather Stations in the Valley

  • Apple - Scab
  • Apple - Powdery Mildew
  • Apple - Fire Blight Prevention
  • Stone Fruit - Brown Rot Blossom Blight
  • European Red Mite
  • Pre-Bloom Insecticides

Weed Management

  • Pruning
  • Fertilizing
  • Liming
  • Planting Trees
  • Nursery Trees
  • Mowing

Pest Management Guides 2021

Events and Notices

  • NSFGA Research Survey
  • Canada GAP Version 9.0 Updates



2021 Degree Day Accumulations

The above-average trend continues. Temperatures have cycled in March and April to sometime give the illusion that it hasn't been very warm. But Jeff Franklin describes that the averages tell the story. The average temperature for March 2021 is 1.35°C compared to the 20 year average of -0.62°C. The average temperature of April 2021 is 7.16°C compared to the 20 year average of 5.59°C.

Please note that due to an IT problem, the degree day accumulations this week are updated to only May 1st, but the issue should be resolved by next week.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to May 1st for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 61% more plant development heat units compared to the 5-year average, and 55% more compared to the 10-year average.
  • Approximately 147% more plant development heat units compared to 2020, and 47% more compared with 2019.
  • Approximately 80% more insect development heat units compared to the 5-year average, and 64% more compared to the 10-year average.

More Weather Stations in the Valley

On track to finish installation this week!

The Nova Scotia Fruit Growers’ Association through federal and provincial funding with the Nova Scotia Department of Agriculture has embarked on a smart farm demonstration project to install and maintain weather stations. 

At the time of this newsletter, eight of the ten weather stations are operational. The Grand Pre location was installed this morning and the Windsor location is being installed this afternoon. Other operational stations include: Atlanta, Aylesford, Grafton, Melvern Square, Mochelle, Morristown, and Woodville. Jon Bent is planning to install the final station in North Medford on Wednesday morning.

This is a reminder that any weather stations on the Davis WeatherLink platform that do not have "NSFGA" in the name are not being maintained under this project. 


Historical weather data is a feature of a paid account so NSFGA members and their advisors have access. On April 22nd, Candy sent the login information to members. If you’re not a member, you can access the live/current weather data by creating your own free account on Davis WeatherLink. Search for weather stations and add them to your account.

Bud Development

An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Over the last week the leaves have started to unfurl into the tight cluster stage. On May 3rd, the Idared buds were at the stage of tight cluster, Honeycrisp was at early tight cluster, and Ambrosia was at half-inch green. Stone fruit are in bloom or approaching bloom. With the extra degree day accumulations this year, bud development is progressing quite early.

Figure 2: Bud development in an early region on Middle Dyke Road in Kentville on May 3rd. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Orchard Outlook committee members reported that Honeycrisp in later regions are generally around late half-inch green to early tight cluster. Pear stages are also variable but on average are between bud burst and green cluster stages.


Apple – Scab

Table 1: Apple scab infection events at the Kentville Research Station from April 28th to May 4th, 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.

Forecast and Perspective

A period of rainfall is currently forecast for Wednesday, May 5th. With the forecast temperatures at an average of +11.5°C, it would take around 12 hours of leaf wetness for an apple scab infection event to occur, according to the Modified Mills TableNote that ascospores are now maturing more rapidly and that 12% of the total spore load has matured since the last infection event. 

The heat is also speeding up ascospore maturity. For perspective, at this time last year only 5% of ascospores had matured.


  • 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.
  • Vigilant protection of primary scab will prevent the challenges that come with chasing secondary scab. Secondary scab will be increasingly challenging with upcoming product discontinuations.
  • Always tank mix single site fungicides with a group M for resistance management.
  • Note that Polyram is being phased-out due to the cancellation of the active ingredient. The last date of use is June 21, 2021.

Special notes on products containing Captan and water soluble packaging:

  • The product formulations Maestro 80 DF and Supra Captan 80 WDG are being phased-out. The last date of use is May 10, 2021 and it is fast approaching. The PMRA identified issues with the dry flowables in terms of applicator exposure when mixing and loading. Studies show that water soluble packaging (WSP) reduces handler exposure so it’s an acceptable risk mitigation measure. There are new registrations for the formulations Supra Captan 80 WSP and Maestro 80 WSP.
  • Water soluble packaging has been used in the past but now we are looking at more frequent use. Consider these best practices:
    • Make sure packets fully dissolve and disperse before adding other products. Packets dissolve faster in warm water than cold water, like dishwasher pods. 
    • Check the filter after the first use and every couple of uses.
    • Be careful mixing. Do not use WSP in a tank mix with boron and rinse the tank well before and after boron.
  • If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.
  • 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 2-24 days).

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.

Fungicide resistance management for scab vs powdery mildew:

Scab: The Group M fungicides (mancozeb and captan) provide scab control so tank mixing them with single-site fungicides is a great strategy to slow resistance development in the apple scab population. Most populations of apple scab are resistant to Group 3 fungicides Nova and Fullback so the products are not expected to provide control. A full rate of a protectant fungicide is necessary for scab control.

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.


  • Do not apply a product for powdery mildew before a heavy rain is expected. The product will wash off, plus powdery mildew spores will not germinate on a wet leaf surface anyway. As opposed to scab, powdery mildew protection should go on prior to a period of warm and dry weather when infections are expected.
  • Application of a protectant mildew fungicide at tight cluster prevents infections of leaf clusters. Timely application early in the season will reduce the risk of secondary infections. 
  • 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.

Apple – Fire Blight Prevention


  • 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. 
  • Be cautious when applying post-emergent herbicides to prevent injury to young trees. 

Stone Fruit – Brown Rot Blossom Blight

Brown rot infection of the flowers during bloom provides secondary inoculum for fruit infections later on.


  • Fungicide protection from brown rot should begin just prior to bloom and be maintained during periods of warm, wet weather. 
  • Rotating classes of brown rot fungicides is key to slow resistance development. There are many options in the management guide.


European Red Mite

To be most effective, oil application for ERM should be targeted close to egg hatch – around tight cluster and before pink. Conditions have been good for getting oil on so applications should be made soon if not already done. Avoid oil if freezing temperatures will occur within 48 hrs.

Pre-Bloom Insecticides

It is still too early for pre-bloom insecticides but with the lead in degree day accumulations this year the time is approaching. Depending on the heat in the forecast, your region, and monitoring reports, action may be needed in a week or two as we approach the pink stage.


  • Be on standby and monitor for the spring caterpillar complex, European apple sawfly, tarnished plant bug, and aphids. 
  • Treatments for spring caterpillars should not be applied too early because product must enter the developing flower clusters where the larvae like to feed to be effective. Treatments should be applied pre-bloom so target the full pink stage. Note that there is a lower tolerance for WM than GPM. Green Pug Moth do not feed directly on developing fruitlets.
  • If treatments for OBLR are required at pink, the treatments should also have some activity on WM and GPM. 
  • If a pyrethroid is applied for tarnished plant bug at pink, it will also have activity on WM and GPM. Similarly, pyrethroids are expected to have some activity on EAS if being applied for other pests.
  • As a reminder, pyrethroids are best used at moderate temperatures (20°C or less) and are harsh on beneficial insects and predator mites. They should only be used where potential losses justify their application.
  • In orchards with a history of damage and high numbers of European apple sawfly catches, an application of Altacor, Assail, Calypso, or Exirel at full pink is recommended to control the adults prior to egg laying.
  • If history of tarnished plant bug damage indicates that pressure is moderate to high, an application of insecticide at full pink can be beneficial.

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.


Residual Herbicides

  • Spring is an ideal time for using residual weed control products and they offer a much longer weed control period than post-emergent products such as Ignite and Glyphosate.
  • Note the differences in the application directions for the residual herbicides Chateau and Alion. 
    • Chateau can be applied to young trees (note specific label directions). Chateau should not be applied after budbreak unless application equipment is shielded to prevent crop injury. 
    • On the other hand, 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 specific label directions).
  • 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.
  • Note that residual herbicides can damage single tree replacements. 
  • If weeds are already present, consider adding a post-emerge to a residual herbicide to achieve control.

Post-emerge Herbicides

  • Some of the perennials are at a susceptible stage now and this is a good management opportunity if you didn't get to them last fall.
  • Take time to allow concentrated products like Roundup to mix into the solution before adding other products.
  • Be careful with tank mixing herbicides. At the Orchard Outlook committee, there was a report that the mixture of Roundup Transorb and 2,4-D Amine herbicide can form a white precipitate. New formulations may behave unexpectedly. If in doubt, consider performing a jar test to test compatibility. The jar test is described in a post by Sprayers 101.



  • If pruning is delayed, plan a strategy to get the most value for your time. Prioritize young blocks and high value varieties and return to low value areas. This strategy is especially important considering the new captan limitations.
  • Ensure that youngest blocks are pruned first so growth is directed into desirable leader and terminal extension. Prune early to encourage vigour or delay pruning to remove vigour.


  • Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth.


  • Be cautious applying lime to orchard blocks now that green tissue is progressed. The force of the lime from the spreader can damage the leaf tissue and buds. The next best opportunity to apply lime again is in the autumn.

Planting Trees

  • Newly planted trees should be pruned for tree structure and supported as early as possible after planting. 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).
  • 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.
  • If fumigating in the spring, observe the warnings on the label prior to planting to avoid crop injury. Leave the soil undisturbed for 10 to 14 days or longer in wet weather. To verify plant safety, follow the safety germination test described on the label for PicPlus.

Nursery Trees

  • Check on nursery trees because buds have grown quickly from full dormant to quarter inch green very quickly. Rootstock tops should be cut so the rootstock does not overpower the bud.
  • 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!
  • 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.


  • Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of pre-bloom insecticide applications. An early start will help keep the orchard floor under control.

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.

NSFGA Research Survey

Before time and energy is put into considering research proposals or applying to funding programs, direct input from members is needed to establish research priorities and propose research interests.

The NSFGA Research Committee is asking for your input on this survey to explain what you need or would like to see in terms of research so that we engage in research that is of benefit to growers, packers, and processors. It is important that we get your opinion on what information would benefit you and/or the apple industry. The survey is expected to take less than 5 minutes to complete. Please complete by Tuesday, May 18th. 

CanadaGAP Version 9.0 Updates

My colleagues over at the food safety team noted in their most recent newsletter:
CanadaGAP has released Version 9.0 of the Fresh Fruit and Vegetables Manual and the Greenhouse Product Manual. These new manuals will take effect on April 1, 2021. To download the new manuals, please visit the CanadaGAP website. The audit checklist for version 9.0 is also now available on CanadaGAP’s website. The Frequently Asked Questions (FAQs) have also been updated to reflect version 9.0 of the CanadaGAP manuals and other important changes made to the program this year.

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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