Orchard Outlook Newsletter Vol. 23, No 12

Tuesday, July 4, 2023


Today's newsletter offers similar reminders to last week with additional comments about the recent rain. Fungicide residues are washed off after 50 to 60 mm of rain and it is not a good time to stretch fungicide spray intervals if it leaves fruit unprotected from summer diseases. There are some additional comments about calcium nutrition, including a link to a worksheet that calculates the elemental calcium you're applying in each spray. Today we had our final meeting of the Orchard Outlook Committee for the summer season, but we are planning to reconvene for some preharvest discussions.


*** Please note that this will be the last weekly issue of Orchard Outlook for the summer. Orchard Outlook will continue to be published occasionally for the remainder of the season. ***


Table of Contents:


Weather
  • 2023 Degree Day Accumulations
  • Recent Precipitation
  • Apple - Scab
  • Fire Blight - Infection Management
  • Apple - Black Rot
  • Apple - Brooks Spot
  • Apple - Flyspeck and Sooty Blotch
  • Codling Moth
  • Aphids
  • Mites
  • Obliquebanded Leafroller
  • Apple Maggot
  • Pear Insects

  • Solstice Reminders
  • Weeds and Root Sucker Management
  • Nutrition (Calcium)
  • Cover Crops
  • Mowing
  • Pruning and Training
  • Summer Hedging
  • On-farm Nursery

Events and Notices

  • Virtual Orchard Meet Up Series - Managing the Uncontrollable
  • Apply for Pesticide Certification Online
  • Fuel Charge Exemption Certificate for Farmers
  • International Fruit Tree Association Summer Study Tour in Nova Scotia
  • NSFGA Orchard Tour (Save the Date)
  • Funding Programs

Pest Management Guides 2023

  • Decision Tables
  • Guides



 

Weather


2023 Degree Day Accumulations

Cumulative degree days are still below the 5- and 10-year averages for plant and insect development but the gap has narrowed (Figure 1).

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to July 4 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 5% less plant development heat units compared to the 5-year average, and 5% less compared to the 10-year average.
  • Approximately 10% less plant development heat units compared to 2022, and 16% less compared with 2021.
  • Approximately 8% less insect development heat units compared to the 5-year average, and 8% less compared to the 10-year average.

Recent Precipitation

Nova Scotia is no stranger to significant quantities of rainfall, but the recent challenge has been the total number of rainy days that have hindered re-application of fungicides. This past June, rain was recorded on a total of 20 days, whereas the average for June is 14 days of rain. 

In terms of quantity, the 25-year average for June is 87 mm but this year 239 mm of rain was recorded. Jeff Franklin explains that: "Extended rainy periods in June and July are not typical but do happen. The years 2019 (June), 2015 (June), 2014 (July) and 2011 (June) all had stretches of rainy weather with 30-day totals over 170 mm, or twice the monthly average. For the months of April, May and June combined we received 315 mm of rain in Kentville compared to the 25-year average of 244 mm. We have more than made up for the dry weather experienced in April and May."



Diseases


Apple – Scab

Primary apple scab infection events in Kentville are complete. There were a total of ten primary infection events observed in Kentville this season with the late April infections being considered light, early May infections were moderate, and late May to June infections were heavy.

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.


Recommendations:

  • The extended period of rainy weather is not a time to consider lengthening spray intervals. Please note that most fungicide residues are washed off by a cumulative total of 50 to 60 mm of rain (2 to 2.5 inches). Summer diseases are a risk if spray programs are stretched to this limit.
  • 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 aware of the re-entry periods on the 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. 
    • Allegro has a short 3-day REI but keep in mind the 28-day PHI.
  • 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.
  • The 2023 Fungicide Decision Table can be used to compare fungicide products.


Fire Blight - Infection Management


Blossom infections from May 28 and June 1 could be showing symptoms if infections were allowed to occur. According to the model, the infection to rattail blooms on June 14 could be visible but this suggestion from the model has not been ground-truthed yet.

Product Recommendations:

  • As soon as you find fire blight infections and when conditions allow, apply Apogee/Kudos (prohexadione calcium). Use a lower rate if trees have not filled their space or the full rate if tree growth is not an issue. Prohexadione calcium has a rainfast period of 8 hours. The benefits of Apogee/Kudos:
    • Helps suppress the progression of infection to buy you time for cutting it out. 
    • Builds protection in nearby trees that may not yet be infected so that if infection were to occur, the spread would be already slowed. Where infections are numerous, apply prohexadione calcium to the entire block considering that ooze can infect at a distance of at least 0.8 km away.
    • Reportedly has the potential to reduce or prevent canker incidence on perennial wood (Acimovic et al. 2021, Plant Disease; thank you to Ian Willick for sharing).
  • If significant infections are present in young, nonbearing trees, consider applying a copper product when weather conditions allow drying on plant tissues. The copper would help to reduce the presence of surface dwelling bacteria which would reduce the risk of infection if tissues became wounded. Please note that copper will not slow or stop existing infections.

Pruning Recommendations:

    • To save time, it is not necessary to sterilize the tools often as long as all of your cuts are in fire blight areas and during dry weather. Several research studies have concluded a lack of benefit from sanitizing tools. Where there is a tradeoff because of limited labour, it is best to work quickly than to sanitize tools.
    • Do not break off branches with fire blight infections as you navigate the orchard. Research shows that the bacteria becomes systemic in the tree because not enough wood is removed. There are then a high number of new infections and significantly more canker tissue and cankers on structural wood. 
    • Prune out fire blight infections on young trees in the current year, don't wait for winter.
    • Remove fire blight strikes at least 2-4 ft below active infections to remove the leading edge of the bacteria. The younger the tree, the deeper the cut. Being aggressive at the first sign of symptoms will help prevent the re-occurrence of symptoms and the need for continuous cutting back. Repeat tree inspections.
    • If you feel confident that you can monitor the formation of a canker on a stub cut for later removal, then a stub cut may be appropriate. A 4-inch stub cut causes a canker to form on the stub before reaching structural wood like the leader of the tree. However, do not forget to remove the stub because otherwise the canker will serve as a source of bacteria. Mark the tree for revisiting.
    • Cut out infections when a period of 2 dry days are in the forecast. Leave prunings in orchard laneways to let dry thoroughly for several weeks. 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.


    Apple – Black Rot


    Recommendations:

      • There is concern about the risk of black rot infections from the extended period of rain. Fungicides are of course best applied preventatively but when that is not possible there may still be benefits of later application in terms of pre-symptom and post-symptom development. Theoretically, fungicides like Captan/Folpan can suppress symptom development and reduce lesion appearance and development of secondary lesions. But if fungicide residues decline then symptom development can proceed. In a roundabout way, I am explaining why this year fungicide rates should not be reduced and spray intervals should not be lengthened yet. Wait for more extended periods of dry weather.
      • The black rot fungus infects fruit during warm rains from petal fall to harvest. The highest risk is from petal fall up until 4 to 6 weeks after bloom.
        • A 10 hr wetting period at 16°C to 32°C allows infection. The optimum temperature for infection is 20°C to 24°C. We do not have a model for black rot infection but protection would need to be targeted prior to wetting and ideal weather conditions.
        • Captan is an effective protectant for high density orchards that have a history of black rot. However, consider Captan where practical in terms of label restrictions for re-entry intervals. Folpan has labelled activity on black rot and a relatively shorter REI for hand thinning of 6 days.
        • There are few management options to cover such a long risk period. Merivon has activity but any group 7 + 11 product should not be used more than 4 times each year.  

      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 (or Folpan 30 days after petal fall).


      Apple - Flyspeck and Sooty Blotch

      These summer diseases develop on the surface of the fruit in midsummer until harvest (Figure 2). 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. 

      There is a lag time between when a spore from flyspeck fungi infects an unprotected apple fruit and when symptoms become visible. A certain number of cumulative wetting hours are needed for flyspeck colonies to grow and become visible. Without getting bogged down in the details, the takeaway is that during rainy years the symptoms may be observed early and during dry years the symptoms are less likely. Regardless, adequate fungicide coverage can stop flyspeck colony growth during periods of leaf wetting and may prevent the appearance of symptoms altogether. 

      Recommendations:

          • Fungicide residues are likely eliminated by 50 mm of heavy rain or 60 mm of cumulative rain. When possible, aim to reapply summer cover sprays before fungicide residue is lost.
          • Fungicides applied after infection can temporarily stop growth of flyspeck colonies but do not cure infections so focus on maintaining fungicide residues. When fungicide residues dwindle below levels that inhibit growth, the flyspeck colonies begin growing again.
          • What if flyspeck growth is arrested all season by consistent fungicide residues and then rains remove residues right before harvest? There is a chance that fruit will not show symptoms if they are harvested and cooled before accumulated wetting requirements. Storage conditions may allow periods of condensation when flyspeck development can progress, but development of symptoms in storage is a symptom of already poor control in field conditions.
          • Include a product for cover sprays that is labelled for flyspeck and sooty blotch such as Captan, Maestro, Inspire Super, Aprovia Top, Allegro, Pristine, Merivon, and Folpan.

          Thank you to Bob Prange for sharing the article by David Rosenberger that I have summarized here. 

          Figure 2: Symptoms of flyspeck infection observed at harvest last year. Summer diseases such as flyspeck are a risk if spray spray programs are stretched beyond the limit. Fungicide residues are washed off after 50 to 60 mm (2 to 2.5 mm) of rain.



          Insects

           

          Codling Moth

          • 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 late application to avoid the heavy rain will preserve the residual activity of the insecticide for all future egg laying. If an insecticide was applied before the extended rainfall, the heavy rain would have washed off the product.
          • If trap captures are below the treatment threshold but continue to build over time then treatment should be applied once a threshold is reached. When the time for apple maggot treatments arrives, the chemistries will also treat late codling moth.
          • The neonicotinoid insecticides (group 4 products) move into plant tissues over a period of about 24 hours. If it rains before the product is absorbed, the product on the surface is susceptible to wash off.
          • Notes about using Imidan:
            • Newly amended labels came into effect on October 30, 2022. Now all hand thinning activities must be completed prior to application. No hand thinning can occur on trees after they are treated with Imidan. Also, a maximum of two applications may be used each year.
            • The product does not penetrate leaf tissue so it is a surface material that is susceptible to wash off under rainy conditions.
            • Approximately a week after application of Imidan, 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.

          Aphids

          • Monitor for aphids in young trees and nursery plantings where feeding can disrupt shoot growth. If leaves are curling high, 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.

          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.
            • Mites thrive in warm and dry weather so conditions have not been overly supportive yet. July is the time of year to control rust mite before foliage becomes bronzed in mid to late August.
            • 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

          • Monitor or check scouting reports for larval populations soon. The caterpillar feeds on terminal shoot growth and also on apples, leaving a scar.

          Apple Maggot

          • In early years, captures in commercial orchards can occur around July 10th. In blocks that are still being treated for codling moth, the control is extended to early maggot flies. However, in organic orchards, hang traps in early July to begin applications of GF-120 Fruit Fly Bait or Surround as soon as monitoring indicates that flies are present.
          • 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 re-entry intervals for hand thinning in order from highest to lowest: Imidan HAND THINNING PROHIBITED, Danitol 23 days, Cormoran 7 days, Assail/Aceta 6 days, Calypso/Theme 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.
          • Significant rainfall will wash off insecticide residues that are needed to ward off apple maggot flies. Re-treatment is required after 10-14 days or cumulative rainfall of 12.5-25 mm (0.5-1 inch). Insecticide residue should generally be maintained through to the end of August.

          Pear Insects

          • Pear Psylla: Refer to the management guide for product options.
          • Pear rust mite: 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 information for apples.



          Horticulture



          Solstice Reminders

          • Top dressing is not recommended after the end of June. Late release will prevent trees from hardening off before the winter. 
          • 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.

          Weeds and Root Sucker Management

          • Note that 2,4-D has an 80-day PHI. Eighty days from now is September 23.
          • 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.
          • 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. AIM herbicide is registered for control of suckers but avoid drift onto young trees and apply only near mature brown bark.
          • Please note there are local reports that the new rootstock G890 has plenty of root suckers and they can show up about 4 ft from the tree.

          Nutrition

          • Consider nitrogen as soon as possible if tree foliage appears pale. Leaching may have occurred during recent heavy rains, especially on sandy soils.
          • Calcium:
            • The goal of foliar Ca sprays is to increase the concentration of Ca in the fruit and reduce the incidence of bitter bit. Begin calcium applications at 4 to 6 weeks after petal fall when fruit have reached the golfball stage at around 35 mm. Calcium applied at two-week intervals is better than occasional, high-rate applications. 
            • 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.
            • The recommended rate is 4 to 14 pounds of elemental calcium per acre over an entire season spread over six to eight cover sprays. Low rates will not cause leaf burn but will likely lead to only minor control of bitter pit and likely will not enhance storage life of the fruit. High rates may lead to some leaf burn, give good control of bitter pit, and may also enhance storage life of the fruit.
            • Determine how much elemental calcium you would like to apply over a season and then work backwards to determine the required number of sprays. For help calculating the amount of elemental calcium you are applying in each spray, visit Penn State Extension to download a calcium rate calculator. The percentage of elemental calcium will be listed on the label. 
            • Calcium chloride flake (77% Ca) is the most economical Ca material to use but also the highest risk for foliar burn. Calcium chloride flake has a low risk of leaf burn when applied at 4.5 kg per 1000 L of spray solution. The risk of leaf or fruit damage from calcium is highest in hot weather. Susceptible varieties can develop lenticel spotting if damaged. Target fast drying conditions for applications.
            • 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/Kudos. Note that nutrient product formulations with calcium may contain boron that would interact poorly with water soluble packaging.

          Cover Crops

          • Perennia has a series of videos about cover crops by Sonny Murray and Rosalie Gillis-Madden that can be accessed from our website.
          • Summer grasses such as pearl millet and sorghum-sudangrass that have been growing in popularity lately can be planted from mid-June until early August.

          Mowing

          • Keeping the orchard floor cover mowed will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.
          • Mowing and herbicide strips help to prevent issues with two-spotted spider mite (John Michael Hardman).

          Pruning and Training

          • Training practices should be done on dry and sunny days, especially in high risk fire blight blocks. Wounds can take about 2 days to heal. Do not work in trees when they are wet from dew.
          • In dry weather, select strong terminals on young trees and remove competing terminals to single the tops.
          • When possible, install trellis and tie trees. 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).
          • Ensure that deer fencing is installed as soon as possible to protect new growth on young trees. Prior to deer fencing, the product Bobbex may be used as a deer repellent but it must be applied proactively and requires frequent application to new growth and after rainfall. Ideally, install deer fencing the year prior to planting.

          Summer Hedging

          • A local study by Perennia in 2013 evaluated the regrowth on summer hedging using Ambrosia on M.9 and Gala. Results indicate that the last week of June = 6 to 21 cm of regrowth, first week of July = 4 to 12 cm of regrowth, and second week of July = 2 to 3 cm of regrowth. No regrowth is expected after terminal bud set around the first week of August although it was not included in the trial.

          On-Farm Nursery

          • Scion leaders need support. Stakes should be placed on the side opposite from the bud so it pulls the bud toward the rootstock rather than away.
          • Monitor for green aphids.
          • 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


          Virtual Orchard Meet Up Series - Managing the Uncontrollable

          Since 2021, the summer Virtual Meetup program has brought together growers, researchers, and government and Extension agents to have an international conversation about important tree fruit topics, connecting industry leaders across North America.

          The third webinar series will focus on the topic of “Managing the Uncontrollable”. The first 30 minutes will feature 2 researchers who will introduce the topic, how it relates to tree physiology, and discuss related research. The last hour will feature a grower and speaker panel to discuss practical applications and challenges that growers across North America are dealing with.

          Webinars will be conducted live on Thursdays at 4:00pm (PST)/7:00pm (EST). The format will be an open discussion and in a very inclusive virtual format. Each webinar will last 90 minutes. The program is free of charge. Videos will be made available for those who missed the meetings. The next meeting is on July 13th about heat. Preregistration is not required to attend. Simply go to https://bit.ly/2023-virtual-meetup to join a few minutes prior to the start of each meeting.

          This effort is being conducted across North America in close collaboration with the International Fruit Tree Association (IFTA), the AI Institute for Transforming Workforce & Decision Support (AgAID), and the Cornell Institute for Digital Agriculture (CIDA).


          Apply for Pesticide Certification Online

          The Nova Scotia Department of Environment and Climate Change is pleased to announce that you can now apply and pay for pesticide certifications online. The new online portal is available here:  Online Application (novascotia.ca).

          The change will apply to new applications, re-certification, and applying for certification through reciprocity:
          • New applicants will be able to apply and pay on-line, making it quicker and easier to book an online exam session. 
          • Certificate holders will be able to renew their pesticides certifications on-line, including uploading proof of points and paying the required fees.
          • The on-line portal will also allow applicants to upload of the required documents when applying for recertification through reciprocity.

          If you have questions or run into any issues with the new online portal, please contact your local ECC office. Regional and District Office Locations | Department (novascotia.ca)


          Fuel Charge Exemption Certificate for Farmers

          This certificate permits the delivery of the fuel without having the fuel charge applied at that time. If you are a farmer by the standard of the Greenhouse Gas Pollution Pricing Act (GGPPA) and you carry out eligible farming activities, give the exemption certificate to the registered distributor that delivers the fuel in accordance with this Act. You can find the form here.


          International Fruit Tree Association Summer Study Tour in Nova Scotia

          The Nova Scotia Summer Tour is shaping up to be two fully-packed days of orchards (Honeycrisp, Ambrosia, Gala, Evercrisp, V-trellis pears), apple rootstocks (NC140 trial, on-farm experiences with G890, G202, others), replant trials, new technologies (over-the-row sprayers, Agbot sprayers, Vivid Machines, leaf removal, irrigation, an Eastern Manufacturing equipment showcase, reflective mulch use), growth regulators (thinning trials, Harvest, ReTain), and of course, the usual discussions of pruning, training, and labor issues, plus a lobster dinner with local music! The tour is on July 23 to July 25. Visit their website for more information.


          NSFGA Orchard Tour (Save the Date)

          We will be beginning and ending the tour at the Kentville Research Station, heading west to visit Annapolis County, with some stops in Kings County on the way back. Discussions will include equipment, compost, living labs research and other local research.


          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.



          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 week the Orchard Outlook Committee discussed rainfall, summer rots, and calcium with the input of this week's participants: Bob Prange, Jeff Wentzell, Karen Burgher, Keith Fuller, Jill MacDonald, Jeff Franklin, and Danny Davison.

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

          By Michelle Cortens at July 04, 2023
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