Update on Degree Days and Precipitation - July 23

Today's post is a brief update on degree day accumulations.

2024 Degree Day Accumulations

Degree day accumulations up until now continue to be similar to warm years such as 2012 and 2021. Temperatures have been average or slightly above-average over the last week which has kept the accumulated degree days high relative to past years. If this trend continues, July may have the the highest accumulated degree days on record.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to July 22 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 9% more plant development heat units compared to the 5-year average, and 10% more compared to the 10-year average.
• Approximately 8% more plant development heat units compared to 2023, and 5% more compared with 2022.
• Approximately 13% more insect development heat units compared to the 5-year average, and 14% more compared to the 10-year average.

Update on Degree Days and Precipitation - July 16

Today's post is a brief update on weather conditions including degree days, soil temperatures, and precipitation.

2024 Degree Day Accumulations

Degree day accumulations up to this point are very similar to warm years such as 2012 and 2021. Current conditions are very close to the highest accumulated base 5°C heat units over the last 17 seasons. If the above-average temperature trend continues, then we are on track to be in the warmest growing season on record.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to July 15 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 11% more plant development heat units compared to the 5-year average, and 11% more compared to the 10-year average.
• Approximately 11% more plant development heat units compared to 2023, and 8% more compared with 2022.
• Approximately 15% more insect development heat units compared to the 5-year average, and 16% more compared to the 10-year average.

2024 Soil Temperature

Soil temperatures are also above the average as shown on the red line versus the black line average.

Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2020 to 2024. Provided by Jeff Franklin(AAFC).

Seasonal Precipitation

From one extreme to the other... the dry spring and early summer months have been followed by heavy precipitation events in early July. Kentville has received 196 mm of rain already in July compared to the 25-year mean of 83 mm for the entire month.

Table 2: Monthly precipitation totals in 2024 compared with the 10-year average. Provided by Jeff Franklin (AAFC) using the Kentville weather station data.

Orchard Outlook Newsletter Vol. 24, No 12 (re-published with correction)

Re-published with correction: The newsletter that was originally published this week on Tuesday, July 9 is being republished to notify you that a change has been made. In the section on 'Horticulture' under 'Nutrition' a misunderstanding was corrected about the quantity of elemental calcium in calcium chloride and thus the amount of calcium applied per spray. The correction and a short explanation shown in red text should clear up any confusion.

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Today's newsletter comes to you after the excessive rainfall on Saturday so we discuss that rain washed off pesticide protection. Periods of heavy or prolonged rain are not a time to lengthen fungicide intervals because summer diseases become a risk. For insect management, there is a new decision table available for comparing the products for use on codling moth and apple maggot. Monitor scouting reports for potato leafhopper and watch for their presence especially in areas of active fire blight infections. There are also reports in berry crops that spotted wing drosophila activity is appearing early this year.

*** 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

• 2024 Degree Day Accumulations
• 2024 Precipitation Update

Diseases

• Apple - Scab
• Apple - Powdery Mildew
• Fire Blight - Infection Management
• Apple - Black Rot
• Apple - Brooks Spot
• Apple - Flyspeck and Sooty Blotch

Insects

• Apple Maggot
• Codling Moth
• Aphids
• Mites
• Obliquebanded Leafroller
• Potato Leafhoppers
• Pear Insects
• Stone Fruit - Spotted Wing Drosophila (SWD)

Horticulture

• Tree Health
• Solstice Reminders
• Cover Crops
• Mowing
• Weed and Vegetation Management
• Nutrition
• Young Trees
• Summer Hedging
• Nursery Trees

Events and Notices

• NSDA Programs Update
• Perennia Webinars: Understanding Alternative Nutrient Amendment

Online Pest Management Guide

 

Weather

2024 Degree Day Accumulations

The degree day accumulations for base 5°C plant development and base 10°C insect development continue to be ahead of the 5- and 10-year averages (Figure 1). Jeff Franklin shares that, "So far in July temperatures have been close to average so we remain in the same position, relative to past years, in terms of degree days."

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to July 8 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 9% more plant development heat units compared to the 5-year average, and 9% more compared to the 10-year average.
• Approximately 11% more plant development heat units compared to 2023, and 4% more compared to 2022.
• Approximately 12% more insect development heat units compared to the 5-year average, and 11% more compared to the 10-year average.

2024 Precipitation Update

It is only early in the month and the Kentville station has recorded 99.6 mm of rain so far in July which exceeds the 25-year average of 82.8 mm. Much of this rain was delivered in a single heavy rainfall event over the course of the day on Saturday, July 6.

Diseases

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.

Recommendations:

• Please note that fungicide residues are washed off by a cumulative total of 50 to 60 mm of rain (2 to 2.5 inches). Most regions in the Valley received enough rainfall on Saturday, July 6 to wash off protection. Periods of heavy rainfall are not a time to lengthen fungicide intervals. Summer diseases are a risk 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. 
• Folpan/Follow becomes a good option at this time of the year for scab control and protection from summer diseases. Note the REI of 12 hrs for general activities and 6 days for hand thinning. Folpan/Follow 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.
• Be aware of the re-entry periods on products for hand thinning. Captan has an REI of 15 days for high density plantings and 24 days for low-density plantings. Alternatively, the product Allegro is a quick re-entry product at only 24 hours but note the 28-day preharvest interval.

Apple – Powdery Mildew

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

Recommendations:

• Trees are susceptible to powdery mildew infections for as long as new leaves are forming on growing shoots (until terminal bud set). This can be challenging for young nonbearing plantings because infections can reduce shoot growth. Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.
• Avoid more than two consecutive applications of products with a group 3, 7, or 11. Powdery mildew resistance to group 11 products was reported in a survey done in 2013 so success is unlikely. Group M products do not have activity on powdery mildew. 

Fire Blight - Infection Management

Recommendations:

• Monitor for shoot blight on suckers that can infect the rootstock.
• 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. Do not work in trees when they are wet from dew.
• As soon as you find fire blight infections, an application of Apogee/Kudos (prohexadione calcium) can help to suppress the progression of infection that buys you time for cutting it out. Use a lower rate if trees have not filled their space or the full rate if tree growth is not an issue. 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.
• 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 branches are not adequately 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.

Apple – Black Rot

Recommendations:

• Based on our limited knowledge, the highest risk of infections is theoretically between petal fall and 4-6 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. 
• There are few management options to cover such a long risk period. 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/Follow has labelled activity on black rot and a relatively shorter REI for hand thinning of 6 days so it becomes an option at this time of the year. Merivon has activity but this group 7 + 11 product should not be used more than 4 times each year. We do not have a model for black rot infection but protection would need to be targeted prior to wetting and ideal weather conditions.
• The fruit cuticle is sensitive to damage at this stage. Be cautious with spray mixtures (calcium, foliar nutrients). 

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, Aprovia Top, or Folpan/Follow.

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, Folpan/Follow, Maestro, Inspire Super, Aprovia Top, Cevya, Allegro, Pristine, and Merivon. Summer diseases such as flyspeck are a risk if spray spray programs are stretched beyond the limit. Adequate fungicide coverage can stop flyspeck colony growth during periods of leaf wetting and may prevent the appearance of symptoms altogether.

Insects

Apple Maggot

• A new resource has been developed to compare the products that are registered for control or suppression of codling moth and/or apple maggot (Figure 2). Note that high label rates are often needed for activity on apple maggot.
• Dr. Suzanne Blatt reports apple maggot trap captures as early as July 2 at the Kentville Research Station. In blocks that are being treated for codling moth, the control is extended to early maggot flies. 
• 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. 
• The economic threshold is 1 maggot fly per orchard on a yellow sticky board. Apply a conventional 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.
• 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.

Figure 2: NEW RESOURCE! An insecticide decision table comparing the products registered for control or suppression of codling moth and apple maggot. Click the figure to visit the full-size PDF file for printing. Thank you to the grower who suggested the creation of this resource!

Codling Moth

• The heavy rainfall on July 6 is expected to have washed off insecticide residues. Re-apply protection because eggs are still hatching that were laid by the first generation flight of moths.
• 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 often 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:
• 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. 
• 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 in spring will also help to delay resistance selection for European Red Mite.

Obliquebanded Leafroller

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

Potato Leafhoppers

• 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. Monitor your scouting reports or updates.
• 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 are the group 4 products and they include Assail/Aceta, Calypso/Theme, Cormoran, and Sivanto Prime.

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.

Stone Fruit - Spotted Wing Drosophila (SWD)

• There are reports that SWD populations are ramping up early this year. They showed up in berry monitoring regions in significant numbers early last week.
• Spotted wing drosophila lay eggs in ripening tender fruit, and larvae may be present at harvest. If monitoring indicates treatment is required, use insecticides weekly. These products rely on contact with spotted wing drosophila adults.
• Products registered for control of SWD in peach/nectarine, plum, and cherry are listed in the Stone Fruit Management Guide. PHI varies widely:
• longer PHIs for Danitol, Harvanta, Imidan, and Malathion (peach/nectarine)
• shorter PHIs for Malathion (cherry and plum), Delegate, Exirel, Entrust, Up-cyde (cherry)
• Note that through the minor use process, the label rate for Malathion 85E was increased for cherries to provide control at 855-2500 mL/ha instead of only suppression at the old rate. The maximum number of applications is 2 while maintaining the same REI and 3-day PHI.

Horticulture

Tree Health

• Check the height of the graft union above the soil line. If frost heaving has occurred it is recommended that you hill soil to cover exposed roots and an overexposed rootstock shank. An overexposed rootstock shank may be more susceptible to winter injury during fluctuating warm winter temperatures. Exposed roots are susceptible to herbicide sprays.

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.

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.
• For August and September plantings of cover crops, check out the new factsheet about Fall Cover Crop Species Selection and Management that was written by Sonny Murray and Caitlin Congdon.

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).

Weed and Vegetation Management

• Note that 2,4-D has an 80-day PHI.
• 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.

Nutrition

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 4.5 to 15.5 kg elemental calcium per ha (4 to 14 lbs 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. 
• CORRECTED: Calcium chloride flake (77% CaCl2) 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 the standard rate of 4.5 kg per 1000 L of water/ha (4 lbs/100 gal/ac).
• Calcium chloride flake is 77% calcium chloride which is composed of one calcium and two chloride molecules. According to the weight of the molecules the calcium portion represents about 28% of the total weight. Therefore, our calcium chloride flake contains 28% elemental calcium.
• For each spray at the standard rate of 4.5 kg per 1000 L/ha, the 28% portion that is elemental calcium is 1.3 kg/ha (1.1 lbs elemental calcium per acre).
• 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.

Young Trees

• 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 vigorous trees, 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. Remove vigorous shoots in the entire canopy but especially at the top. 
• If there is fire blight in a block then there is a greater risk of spreading it by summer pruning than dormant pruning.

Nursery Trees

• 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!
• Budding
• As August approaches, find a source of bud wood that does not have a history of fire blight strikes. Trees that have shown signs of fire blight strikes or that are situated near fire blight infections should be eliminated as a source of bud wood. Cut bud wood fresh every morning if possible.
• Occasionally sanitize all tools used for bud wood collection, storage, and budding by washing in detergent and water and disinfecting with sodium hypochlorite bleach. During bud wood collection and budding, frequently spray hand tools with fresh sodium hypochlorite bleach solution, diluted one part to nine of water.

Events and Notices

NSDA Programs Update

Programs staff would like to inform clients that applications are being accepted at this time for the following 2024-2025 programs. Programs for the 2024-2025 year, along with their applications and guidelines can be found at the following links:

• Advancing Clean Technologies Program - July 15th, 2024
• Limestone Trucking Assistance Program
• Get Growing Program
• Wildlife Damage Mitigation Program
• On-farm Electrical Preparedness Program
• Planning New Opportunities Program
• Speaker Series Assistance Program 

*NEW* On-farm Technology Adoption Program - Government of Nova Scotia, Canada

• Investments in advanced technology that provide labour efficiencies, reduce cost of production, increase yields
• 50% cost share, to a maximum of $10,000
• Application Deadline: August 15, 2024

*NEW* On-farm Automation and Innovation Program - Government of Nova Scotia, Canada

• Supporting innovative technologies that require testing and knowledge sharing in NS before widespread adoption
• 50% cost share, up to $30,000
• Application Deadline: August 15, 2024

*NEW* Apiculture Sustainable Growth and Health Program - Government of Nova Scotia, Canada

• The objective of the program is for hive health, commercial crop pollination expansion and adoption of efficient technologies.
• Stream 1 Pollination Expansion now has three categories of support based on the amount of hives used for pollination in 2023.
• In stream 1 applicants can now also apply for nucs, queens and queen cells.
• Application Deadline: August 15, 2024

For more information on these programs please contact your Ag Rep.

Perennia Webinars: Understanding Alternative Nutrient Amendment

You’re invited to a summer webinar series with local and passionate professionals discussing the world of nutrient amendments that can be used to help producers in transitioning from synthetic nitrogen fertilizer, assist in utilizing resources, and adding nutrient and microbial diversity in agricultural systems through the use of composts, manure, by-products, and more. For more information and to register, visit the Perennia website.

Online Pest Management Guide

Beginning this year, all of the pest management guides are available from an online tool. On the tool you will find guides for organic and conventional apples, pears, peaches/nectarines, plums, and sour/sweet cherries. You can search and filter the information and/or print. To help you navigate the guide, we have developed a brief tutorial video as well as a how to use guide.

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

Orchard Outlook Newsletter Vol. 24, No 11

Today's newsletter discusses fire blight infection management in terms of product and pruning recommendations. Now that you may be considering lengthening your fungicide spray intervals, be careful because fungicide residues are washed off after 50 to 60 mm of rain and stretching spray programs beyond the limit allow summer diseases such as flyspeck to take hold. There are some additional comments about mites and apple maggot, exposed rootstock shanks, calcium nutrition, and summer hedging. 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 Michelle is away next week and no newsletter will be published for the week of June 30. The newsletter will resume the following week of July 8.***

Table of Contents:

Weather

• 2024 Degree Day Accumulations
• 2024 Spring Precipitation

Diseases

• Apple - Scab
• Apple - Powdery Mildew
• Fire Blight - Infection Management
• Apple - Black Rot
• Apple - Brooks Spot
• Apple - Flyspeck and Sooty Blotch

Insects

• Codling Moth
• Scale Crawlers
• Aphids
• Mites
• Obliquebanded Leafroller
• Apple Maggot
• Pear Insects

Horticulture

• Tree Health
• Solstice Reminders
• Cover Crops
• Mowing
• Weed Management
• Nutrition
• Young Trees
• Summer Hedging
• Nursery Trees

Events and Notices

• Marbicon Pesticide Exam Preparation Courses
• Perennia Webinars: Understanding Alternative Nutrient Amendment
• 2024 Virtual Orchard Meetups Series

Online Pest Management Guide

 

Weather

2024 Degree Day Accumulations

The degree day accumulations for base 5°C plant development and base 10°C insect development are ahead of the 5- and 10-year averages and have gained slightly over the past week (Figure 1). On some days in May and June the temperature has been so far above-average that the mean daily temperature has exceeded the 25-year average daily maximum temperature.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to June 24 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 13% more plant development heat units compared to the 5-year average, and 14% more compared to the 10-year average.
• Approximately 23% more plant development heat units compared to 2023, and 6% more compared to 2022.
• Approximately 20% more insect development heat units compared to the 5-year average, and 21% more compared to the 10-year average.

2024 Spring Precipitation

The 25-year average precipitation for the months of April, May and June is 255 mm. So far this year the accumulation has been 125 mm, which is far below average. Jeff Franklin compared the records over the last 112 years to show that the year 2024 is the fourth lowest total precipitation over this period of time.

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 light to moderate infection rates. Microclimates throughout the valley might have observed different conditions with this year's variable rainfall. The most notable infection period was on May 26 with a release of 74.5% of total seasonal ascospores (early leaves on terminal shoots were most tender and susceptible).

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:

• It has now been about 2 weeks since the ascospores were depleted, according to model predictions. Before you consider lengthening spray intervals, take a close look at the leaf canopy in the orchard to determine your risk of secondary infections. Lesions usually first develop on the underside of a leaf and they are velvety brown in appearance. Check cluster leaves for early infections and the mature leaves on terminal shoot growth for mid season infections. 
• Monitor for extended or heavy periods of rainfall because 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/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting. If petal fall was on June 1, then you may consider using Folpan/Follow at the start of July for this timeline to be satisfied.
• Pears: For pear scab, Allegro and mancozeb are NOT registered uses. Captan may be used 2 times for low density and 10 times for high density. Note that for pears, Scala and Luna Tranquility have a 72 day preharvest interval. The registered products are listed in the online guide under Tree Fruit and Pears.

Apple – Powdery Mildew

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

Recommendations:

• The forecast of cool and rainy periods this week would suggest a respite from powdery mildew infections.
• Trees are susceptible to powdery mildew infections for as long as new leaves are forming on growing shoots (until terminal bud set). This can be challenging for young nonbearing plantings because infections can reduce shoot growth. Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.
• Avoid more than two consecutive applications of products with a group 3, 7, or 11. Powdery mildew resistance to group 11 products was reported in a survey done in 2013 so success is unlikely. Group M products do not have activity on powdery mildew. 

Fire Blight - Infection Management

Recommendations:

• 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. Do not work in trees when they are wet from dew.
• As soon as you find fire blight infections, an application of Apogee/Kudos (prohexadione calcium) can help to suppress the progression of infection that buys you time for cutting it out. Use a lower rate if trees have not filled their space or the full rate if tree growth is not an issue. 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.
• 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 branches are not adequately 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.

Apple – Black Rot

Recommendations:

• Based on our limited knowledge, the highest risk of infections is theoretically between petal fall and 4-6 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. 
• There are few management options to cover such a long risk period. Captan has activity but note the REI for orchard activities. Merivon has activity but this group 7 + 11 product should not be used more than 4 times each year. Folpan has activity but should not be applied until 30 days after petal fall to avoid russet. We do not have a model for black rot infection but protection would need to be targeted prior to wetting and ideal weather conditions.
• The fruit cuticle is sensitive to damage at this stage. Be cautious with spray mixtures (calcium, foliar nutrients). 

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. 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, Cevya, Allegro, Pristine, and Merivon (or Folpan 30 days after petal fall). Summer diseases such as flyspeck are a risk if spray spray programs are stretched beyond the limit.

Insects

Codling Moth

• Don't mistake the damage from European apple sawfly as codling moth damage. Codling moth are only just starting to hatch. If you have observed frass and tunnelling on fruit before now then it is caused by sawfly (Figure 2). It appears as though quite a bit of sawfly feeding happened this year, likely because of the sudden onset of heat that sped into bloom and made pre-bloom insecticide application challenging.
• 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 but will still provide residual activity for future egg hatches.
• 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:
• 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.

Figure 2: Damage from European apple sawfly occurred around bloom time and showed up on small fruitlets (left). Sawfly damage should not be confused for codling moth damage (right). Codling moth larvae are just beginning to hatch now.

Scale Crawlers

• The scale that are under a waxy coating at this time of year are the adults that are about to give birth to live young. Those live young are the crawlers that leave the waxy coating and become susceptible to insecticides. Typically the crawlers are active in July but with the heat this year they could be on the move sooner. 
• Monitor for activity by using traps that are made by using black electrical tape (with adhesive side out) around the scaffold limbs of trees, in areas with known infestations. Crawlers yellow bodies will be caught on the tape.
• When the crawlers are active, using one of the neonicotinoid products Assail/Aceta, Calypso, Closer, and Sivanto Prime or Movento for insect control of labelled pests would offer the side benefit of affecting crawlers.

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. 
• 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 in spring 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

Tree Health

• Check the height of the graft union above the soil line. If frost heaving has occurred it is recommended that you hill soil to cover exposed roots and an overexposed rootstock shank. An overexposed rootstock shank may be more susceptible to winter injury during fluctuating warm winter temperatures. Exposed roots are susceptible to herbicide sprays.

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.

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

• Mowing will help to conserve moisture so that it is not transpired by the large surface area of tall weeds and grasses. Mowing and blowing the clippings into the tree row can also help to conserve moisture.
• Mowing and herbicide strips help to prevent issues with two-spotted spider mite (John Michael Hardman).

Weed Management

• Note that 2,4-D has an 80-day PHI.
• 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.
• Create a plan for the whole year. Put on residual products before weeds emerge and use the post-emerge products as backup.
• If using glyphosate alone, consider coarse droplets and low pressure to reduce drift. Use Ignite during hot days in full sun if possible.
• Understand and consider using more Venture for grass control in young orchard. Venture is slow to work (2-3 wks) but you can check for activity by removing the flag leaf on treated grass and examining the base of that shoot for rot.
• Add Prowl H2O or Dual II Magnum to improve your grass control spectrum in young orchard. These pre-emerge products won’t work for bluegrass species however.
• Sinbar is good for pre-emerge grasses in young orchard.
• Lontrel is a great post-emergent for vetch, clovers, and sheep sorrel.
• Chateau has activity on Ragweed whereas Authority does not.
• 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.

Nutrition

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.

Young Trees

• Start selecting strong terminals on young trees and remove competing terminals to single the tops if there are no re-entry intervals active.
• Pruning and training practices should be done on dry and sunny days, especially in blocks with high risk of fire blight. Wounds can take about 2 days to heal. Do not work in trees when they are wet from dew.
• 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 requires frequent application to new growth and after rainfall.
• 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).
• 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.

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.

Nursery Trees

• 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

Marbicon Pesticide Exam Preparation Courses

Marbicon Inc. / Jim Jotcham is offering another round of in-person exam-preparation courses (T2380).
5 recertification points are available (you can only get credit for T2380 once).
The following locations and dates are confirmed.
June 26 Weds – New Germany - Anglican Church Hall, 5311 Hwy 10.
June 27 Thurs – Berwick – Berwick Legion Hall, 232 Main St.
June 28 Fri – Truro – Douglas St Recreation Centre, 40 Douglas St.

The full course, preparing for the exam (all pesticide applicator categories), is $125.
Doors open at about 8:30. Instruction starts at 9:00. Expect to be done around 4:00-4:30.
For only 5 .0 recertification points (T2380), the fee is $110 and finished by around 3:15 pm.

A manual is provided. Bring a pen or pencil.
Food & drink is not offered. Bring your own or go buy it.
NOTE: Pesticide exams are normally written online, NOT at this course.
Contact NS Environment for further details on writing the exam.
A course is not required before challenging the pesticide exam, but it usually helps.

HST is included in the above prices.
Cash or cheques (payable to Marbicon Inc) or e-transfer (marbicon@eastlink.ca).
If paying by e-Transfer, please add a message (for who and for which course).
Pay at the door or by corporate/government purchase order. Sorry, no Visa, MC, or Debit.
Contact Jim Jotcham at marbicon@eastlink.ca or at 902-538-7101 for more details and/or to pre-register.

Perennia Webinars: Understanding Alternative Nutrient Amendment

You’re invited to a summer webinar series with local and passionate professionals discussing the world of nutrient amendments that can be used to help producers in transitioning from synthetic nitrogen fertilizer, assist in utilizing resources, and adding nutrient and microbial diversity in agricultural systems through the use of composts, manure, by-products, and more. For more information and to register, visit the Perennia website.

2024 Virtual Orchard Meetups Series

Every Thursday until June 27 at 8:00 PM Atlantic time
Since 2021, the North American Summer Virtual Meetup Program has brought together growers, researchers, extension, and government to have a conversation about important tree fruit topics. Connecting industry leaders across North America, over 20 experts are involved in these 90-minute online forums, interacting with more than 1,000 participants.

The fourth series will focus on "Water Wisdom: Navigating Tree Fruit Production Through Drought and Deluge". Over the past decade, growers have experienced unpredictable rainfall, water availability challenges, droughts and deluges. We want to explore methods for adapting to these challenges and discuss alternatives for efficient irrigation practices, including advances in irrigation technologies that help growers produce high quality fruit.

In addition to the primary speakers, viewers are invited to share solutions, ask questions, and interact with the specialists and grower panelists. Preregistration is not required to attend. To join, simply go to the Meet-Up Zoom Site. If you can't access, copy and paste the URL in your browser. https://bit.ly/2024-virtual-meetup

Topics

• JUNE 27: Water Wisdom Unplugged: Panelist Q&A

Online Pest Management Guide

Beginning this year, all of the pest management guides are available from an online tool. On the tool you will find guides for organic and conventional apples, pears, peaches/nectarines, plums, and sour/sweet cherries. You can search and filter the information and/or print. If you wish to view growth regulators only, then under the 'Advance Search' for 'Pesticide Type' choose growth regulator. To help you navigate the guide, we have developed a brief tutorial video as well as a how to use guide.

This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Larry Lutz, Jeff Franklin, Joan Hebb, Harrison Wright, Ian Willick, Jessica D'Entremont, Heather Rand, Keith Fuller, and Jill MacDonald.

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