Orchard Outlook Newsletter Vol 21, No 14

Tuesday, July 13, 2021


Table of Contents:

  • 2021 Degree Day Accumulations
  • Seasonal Precipitation

  • Apple - Scab
  • Apple - Powdery Mildew
  • Fire Blight - Orchard Management & Trauma
  • Apple - Summer Diseases
  • White apple leafhopper
  • Potato leafhopper
  • Aphids
  • Codling moth
  • Mites
  • Leafroller
  • Apple maggot
  • Summer Pruning or Hedging
  • Pruning and Training
  • Young Trees
  • Calcium Nutrition
  • Weed Management
  • Nursery Trees
  • Mowing
Pest Management Guides 2021

Events and Notices
  • Agriculture Weather Station Assistance Program Launched for Nova Scotia
  • Perennia Virtual Field Days!
  • Bitter rot and apple scab samples for AAFC
  • Perennia has moved to downtown Kentville!
  • Agricultural Clean Technology Program
  • Website for Perennia's Plant Health Lab



2021 Degree Day Accumulations

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to July 12th for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 13% more plant development heat units compared to the 5-year average, and 11% more compared to the 10-year average.
  • Approximately 12% more plant development heat units compared to 2020, and 26% more compared with 2019.
  • Approximately 17% more insect development heat units compared to the 5-year average, and 14% more compared to the 10-year average.

Seasonal Precipitation

Figure 2 is a graph of cumulative precipitation over the last ten years including rainfall and the rainfall equivalent from snow. This year's precipitation totals (red line) are tracking below the 10-year average (black line).

Figure 2: Both rainfall and the rainfall equivalent from snow at the Kentville Research Station from 2012 to 2021. Provided by Jeff Franklin (AAFC).


Apple – Scab

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.


  • Plugged sprayers warning - You are already aware that water soluble packaging should not be tank mixed with boron and that the tank should be rinsed well before and after boron. Sometimes boron is not the target nutrient in a product but it is included. Please carefully review nutrient formulations that might contain boron in small quantities.
  • Folpan cautions - Folpan is not a new product but it is new for use in the industry. It is considered a cousin to Captan and is similarly a hot product that has the potential to cause fruit russetting. Do not use Folpan close to oil sprays or products containing surfactants. Also, be wary of tank mixes with liquid nutrients that are formulated to maximize uptake.
  • Hand thinning REI reminder - Be very aware of the re-entry periods on the new captan-containing product Maestro 80 WSP for planning ahead to hand thinning. High-density plantings with a maximum canopy width of 2 m have an REI for hand thinning of 15 days. Otherwise, low-density plantings have an REI of 24 days for hand thinning. 
  • Summer Programs - Where the pressure from secondary scab lesions is low, the interval between sprays could be stretched to summer programs (~10 day interval) especially in dry weather. However, note the risk of summer diseases if spray programs are stretched to the limit. Once the 10-day interval has been reached, it is better to re-apply fungicide protection prior to rainfall/possible infection rather than after. 
  • 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 July 13th would require until September 28th to meet pre-harvest requirements for the United States. Even the 45 day PHI is approaching for early varieties such as Paula Red and Jerseymac.
  • Always tank mix single site fungicides with a group M for resistance management.

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.
  • Powdery mildew will continue to spread until terminal bud set. Remember that late summer sprays are protectants for new tissue and they are not eradicants on previously infected tissue.
  • Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.

Fire Blight - Orchard Management & Trauma


  • Monitor for symptoms of trauma blight from winds on July 10th. Sustained winds were low but wind gusts caused some leaves to break at the midrib.
    • According to the Maryblyt Model, trauma blight symptoms could become visible by July 17th. Please note that the progression of trauma blight symptoms according to the model has not been validated in Nova Scotia but the timing can be used for guidance.
  • Continue to monitor for signs of fire blight infections, especially in young blocks. Continue to prune out infected shoots as they appear. Revisit the block every couple of days until no new shoot infections are found. Fire blight will continue to spread rapidly while there is active shoot growth.
  • 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. 
  • Cut out infections when a period of 2 dry days are in the forecast. Drop shoots into the laneways to let dry thoroughly. If cutting a whole tree consider letting it dry while attached to the trellis. Don’t make piles that will prevent the wood from drying. 
  • 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.
Figure 3: Wind gusts early on July 10th created open wounds that were susceptible to fire blight trauma blight infections. Active ooze is present throughout most regions and shoots are still actively growing. The Maryblyt model predicts that trauma blight symptoms could show as early as July 17th (guidance only - not validated). Photos taken yesterday on July 12th.

Apple - Summer Diseases

Refer to the previous newsletter from July 6th for recommendations to control summer diseases such as brooks spot, flyspeck, sooty blotch, and black rot/frog-eye leaf spot.


Apple Insects

  • White apple leafhopper: 
    • The first generation is nearing the end when there will be only adults on trees. The nymphs will start to appear again and cause feeding damage in early August so the second generation is the next treatment opportunity.
  • Potato leafhopper:
    • The potato leafhopper feeds on the young leaves of terminal shoots leading to yellowing at leaf edges, and cupping that will eventually turn brown. Adults are pale yellow-green and walk sideways whereas the white apple leafhopper is white and moves forward and back.
    • Erika Bent APM reports that potato leafhopper has been found throughout the Valley beginning June 26th.
    • Potato leafhoppers can transmit fire blight. Their presence in young plantings and nurseries is concerning, especially in areas of active fire blight infections. Insecticides labelled for leafhoppers include Assail/Aceta, Calypso, and Sivanto Prime.
  • Aphids:

    • Monitor for green apple aphid. In young trees the aphids can disrupt shoot growth. Monitor nursery plantings as well. In bearing plantings the aphids can colonize fruit clusters and damage fruit. 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: 
    • Continue to monitor traps for late moth flight and treat as soon as the threshold for treatment has been reached. If 10 or more moths are caught 7 to 10 days following a treatment then apply a treatment. When the time for apple maggot treatments arrives, the chemistries will also treat late codling moth.
  • Mites: 
    • Scout your orchards or check your scouting reports to see if there is a treatable population. Mites thrive in warm and dry weather.
    • 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.
    • This is the time of year to get rust mite under control instead of mid to late August when the foliage has become bronzed.
    • 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: 
    • The timing is still a bit early but soon monitor or check scouting reports for larval populations.
    • The caterpillar will feed on terminal shoot growth and also on apples, leaving a scar.
  • Apple Maggot: 
    • Dr. Suzanne Blatt and Kim Hiltz at the research station reported their first capture of two maggot flies on Monday, July 12th. A few captures in commercial orchards have also begun according to Erika. In blocks that are still being treated for codling moth, the control is extended to early maggot flies.
    • 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.
    • Note the different re-entry intervals for hand thinning: Imidan 30 days, Danitol 23 days, Assail/Aceta 6 days, Calypso 12 hr, Exirel 12 hr, Harvanta 12 hr, Vayego 12 hr, and Delegate (suppression) 12 hrs. Note that Calypso has a PHI of 30 days.
    • Clean maggot traps 7 to 10 days after treating a block for maggot and monitor for new trap captures. Retreat if new maggot flies are caught.
    • In organic orchards, Surround can be used to deter egg laying and GF 120 fruit fly bait can be used for suppression of adult flies. Both Surround and GF 120 should begin to be applied as soon as flies are present in the orchard. 


Summer Pruning or Hedging

  • Delay summer pruning until terminal buds have been set on vegetative shoots. Pruning prior to this on vigorous trees can promote bud break and weak shoot growth. 
  • In cases with a lot of shoot growth, summer pruning could be a good opportunity to expose the fruit to light and improve fruit colour. 
  • If your goal is to produce a terminal fruit bud on nonvigorous and dwarfed trees then hedge before terminal bud set in order to get some shoot regrowth. The later you hedge, the shorter the regrowth and the less chance of terminal buds. Past trial work showed that an early July timing at 8 to 10 leaf stage was best for encouraging terminal bud set on Gala/M.9.
  • If there is fire blight in a block then there is a greater risk of spreading it by summer pruning than dormant pruning.

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.
  • Maintain good weed control during July and August on young plantings that need to develop vegetative growth. Studies have shown that weed competition during this time can have a significant negative impact on early cropping of young blocks.

Calcium Nutrition

  • Note that nutrient product formulations with calcium may contain boron that would interact poorly with water soluble packaging.
  • 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.
  • 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.
  • Prevent herbicide drift by avoiding sprays during wind gusts, periods of dead calm, wind speeds above 16 km/hr, and temperatures above 25°C.
  • 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.
  • 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.

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.

Agriculture Weather Station Assistance Program Launched for Nova Scotia

The Nova Scotia Department of Agriculture and Perennia have launched the Weather Station Assistance Program. The objective of the Farm Weather Station Program is two-fold: to encourage producers to install weather stations and adopt new technology tools; and fully utilize the data to make proactive management decisions to mitigate the impacts of climate change and adverse weather conditions. For more information, view the earlier announcement.

Perennia's Virtual Field Days!

Join us for this year's Virtual Field Days taking place throughout the month of August! Each week, Perennia specialists will host a 30 minute virtual field day, followed by a question and answer period. For more details, click on the link to register.

Refining Horticulture - August 3, 2021, at Noon (Register)
Technology in Agriculture - August 10, 2021 at Noon (Register)
Optimizing Production - August 17, 2021, at Noon (Register)
Livestock Management - August 24, 2021 at NOON (Register)

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. 

View a research update from past work hereParticipants who provide a site for collection of bitter rot samples will have the species in their orchard identified and they will be informed of the fungicide sensitivity profile for that species.

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. 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.

Agricultural Clean Technology Program

This adoption stream will support the purchase and installation of commercially available clean technologies and processes with a priority given to those that show evidence of reducing greenhouse gas (GHG) emissions, and other environmental co-benefits. Funding will be specifically allocated towards projects under the priority of green energy and energy efficiency. There is a maximum contribution of 50% from the program for For-Profit operations and up to 75% for Not-For Profit organizations. For specific examples, check out the applicant guide.

Website for Perennia's Plant Health Lab

Perennia’s Plant Health Lab is excited to announce the launch of their new website! On our new site, you will be able to find information about our services, our specialists, pathogens of concern, and how to submit samples. If you are interested in dropping off a sample from your farm for analysis, please get in contact with a crop specialist or follow the instructions on our website, and drop it off at our new Kentville office located at 28 Aberdeen Street between the hours of 8:00 am - 4:30 pm. Alternatively, you can contact our lab specialists for more sampling information details. Please visit our new website at: https://www.perennia.ca/agriculture/plant-health-lab/

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

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