Orchard Outlook Newsletter Vol. 23, No 4

Tuesday, May 9, 2023

This week the newsletter notifies you of significant spore load for the next apple scab infection period. There are also ideal conditions for powdery mildew infection this week in warm and dry weather during the tight cluster stage. We discuss early notices about pre-bloom insect management and note that dandelions are in full bloom so mowing is encouraged to reduce the risk of insecticides to bees. The warmer temperatures may be a good opportunity for burndown herbicides Ignite and 2,4-D. We also revisit signs of winter injury. Thanks to the ongoing commitment of the Orchard Outlook Committee members.


Table of Contents:


Weather
  • 2023 Degree Day Accumulations
  • 2023 Soil Temperature
  • Apple Bud Growth
  • Peach Bud Update
  • Cherry Bud Update
  • Winter Injury Revisited
  • Apple - Scab
  • Apple - Powdery Mildew
  • Apple - Fire Blight Prevention
  • Apple - Calyx/Blossom End Rot (Advance Notice)
  • Apple - European Red Mite
  • Nematode (pre-plant samples)
  • Looking Ahead to Pre-Bloom Insecticides

Weed Management

  • General
  • Pollination
  • Grafting
  • Mowing
  • Pruning
  • Fertilizing
  • Liming
  • Planting
  • On-farm Nursery

Events and Notices

  • NSFGA Growing Good Growers
  • Funding Programs
  • Pesticide Training Opportunities by Marbicon

Pest Management Guides 2023



 

Weather


2023 Degree Day Accumulations

Cumulative degree days are now slightly behind the 5- and 10-year averages for plant and insect development (Figure 1). 

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 8 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 12% less plant development heat units compared to the 5-year average, and 10% less compared to the 10-year average.
  • Approximately 7% less plant development heat units compared to 2022, and 30% less compared with 2021.
  • Approximately 16% less insect development heat units compared to the 5-year average, and 22% less compared to the 10-year average.


2023 Soil Temperature

The soil temperature at 35 cm depth has returned to average after the cooling effect of rain (Figure 4). The temperature measures around 9.5°C.

Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2020 to 2023. Provided by Jeff Franklin (AAFC).



Tree Growth


Apple Bud Growth

An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on May 8, the Idared buds were at tight cluster, Honeycrisp was at early tight cluster and Ambrosia was at late 1/2 inch green (Figure 2). Orchard Outlook committee members also report that varieties are at similar stages in Falmouth, Morristown, and Melvern Square. Pear buds in Morristown were at the late bud burst stage.

Figure 3: Bud development in an early region on Middle Dyke Road in Kentville on May 8. Shown from left to right: Idared, Honeycrisp, Ambrosia.

Peach Bud Update

There are some signs of vegetative growth on peach trees but the growth is weak and can still result in bud abortion (Figure 4, left and centre). Terminal vegetative growth appears comparatively healthy and strong (Figure 4, right). Reportedly where a small percentage of peach buds are still viable, blossoms have already been observed on early varieties.

Figure 4: Peach buds affected by winter injury. A vegetative bud is growing slowly (left). The vegetative bud is actually aborting (centre). The terminal bud appears stronger and healthier (right). Photos taken on May 5, 2023. 

Cherry Bud Update

Cherry buds appear normal at the green tip stage but looks can be deceiving (Figure 5, left). The cherry fruiting buds that I have observed are empty inside and do not contain reproductive parts. It is possible for different tissues in the bud to have different cold hardiness levels. Some of the floral tissues survived but not the components required to set fruit.

Figure 5: Sweet cherry buds affected by winter injury. Buds appear to be growing normally but looks can be deceptive (left). The flower is empty of reproductive parts (centre and right). Photos taken on May 5, 2023. 

Winter Injury Revisited

There have been some isolated reports of apple tree damage that may be related to the cold winter temperatures. The damage being observed is bark splitting and blackened heartwood that is leaking sap. Winter injury during the year 1980-81 also resulted in injury to lower scaffold limbs and crotches of the main scaffolds, and some bark separation and splitting. 

Studies have shown that there is no value in sealing or painting the splits, and the tree should be allowed to seal over naturally. A healthy tree will callus over and close completely.

Figure 6: Apple tree health possibly affected by winter injury. Gala/M7 with recent bark splitting (left). Jonagold/M26 with blackened heartwood (right). Photos taken on May 5, 2023. 


Diseases


Apple – Scab


Table 1: Apple scab infection events in Kentville from May 1 to May 9, based on the Modified Mills Table. 
1 For a high inoculum orchard, a significant number of spores can be released during darkness, so begin calculating leaf wetting regardless of the time of day when the wetting event started. An orchard is considered to have a high inoculum load if last season it had 100 or more scabby leaves observed over 600 shoots.
2 Assuming a green tip date of Saturday, April 15th. Please use this as a guide because microclimates will cause conditions to vary on individual farms.
Note: The environmental conditions for an infection are listed in the Modified Mills Table.


Wetting also occurred on May 8 at 4:30 PM for an estimated 17 hours of wetness at 4.9°C. It was not sufficient to cause infection (minimum 26 hours of leaf wetness required).



Recommendations:

  • According to the forecast, ascospores are expected to mature rapidly at a rate of 3-7% per day and within the next five days about 47% of total seasonal ascospores are expected to be mature.
  • The next apple scab infection will have a significant spore load available. 
  • Apply a protectant fungicide to green tissue prior to an infection event on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth. Otherwise, waiting for rain is a gamble with the hopes that protection is applied in time (and the possibility of relying on post-infection treatment).
  • Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
  • Remember that there is a new label for Manzate (mancozeb). The product may be applied 4 times/ha/year, the re-treatment interval is 7 days, the REI for hand thinning is 35 days (12 hrs for all other activities), and the PHI is now 77 days.
  • Alternatives to Manzate for resistance management? Captan may be applied if it is not 7-14 days within an oil. Allegro may be applied 1 day after an oil.
  • If you plan to use oil for European Red Mite control, Captan and Folpan/Follow should be avoided within 7-14 days of an oil application.


Apple – Powdery Mildew

Typically, conidia are released around the tight cluster stage. Powdery mildew infections can be expected when conditions are warm (10-25°C), humid and dry.

Recommendations:

  • Powdery mildew protection should be applied prior to a period of warm and dry weather when infections are expected. Ideal conditions for infection are expected this week.
  • When using Nova, the water soluble packaging should not be mixed with oil or boron.  
  • Apply two sprays targeting powdery mildew prior to bloom on the re-application schedule noted on the product being used (usually 7-14 days). Coverage during the pink to bloom stage prevents fruit infection.
  • Remember to treat young plantings because severe infections can reduce shoot growth, which is most concerning for young, non-bearing orchards.
  • Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.
  • Practice resistance management:
    • Powdery mildew: Group Ms do not have activity on powdery mildew so they will not help prevent powdery mildew resistance development. Products in the groups 3, 7 and 11 are registered for control of PM. Resistance to group 11 products was reported in a survey in 2013. Therefore, whenever the remaining groups 3 & 7 are used, careful consideration must be given to rotating the groups to slow resistance development. Avoid more than two consecutive applications of a single group.
    • Scab: Although Group 3 fungicides Nova and Fullback are also labeled for apple scab, they are not expected to provide control because of resistance in the local scab population. Another product is required for scab protection.


Apple – Fire Blight Prevention

Typically the ooze begins to appear between tight cluster and early pink. Initially the ooze is a watery light tan that darkens to amber. When the canker blight bacteria are active, water sprout shoots close to cankers will wilt. 

Recommendations:

  • Isolated hail was reported on May 8 near the north mountain around Grafton and Lakeville. A fire blight trauma alert was sent by email to subscribers. If hail created wounds then trees are at risk of trauma infection by bacteria from overwintering cankers. Warm temperatures are not a requirement for trauma blight.
  • Pruning practices should be done on dry and sunny days, especially in high risk blocks. Wounds can take about 2 days to heal. Do not work in trees when they are wet from dew.
  • Be cautious when applying post-emergent herbicides to prevent injury to young trees. 
  • Apogee/Kudos (prohexadione calcium) supress shoot blight. The timing of the first application at 2.5-7.5 cm of new shoot growth is critical to success.
  • If interested in pinching buds on young trees the practice can begin around the bud separation stage when it's possible to avoid removing the terminal shoot. Pinching buds becomes risky as bloom begins because fire blight bacteria grow on the flower stigma and are expected to be present in high numbers in warm weather. Do not pinch flowers when tissues are wet. This practice is time-consuming.


Apple – Calyx/Blossom End Rot (Advance Notice)

The disease is caused by the organism Sclerotinia sclerotiorum. Infections develop when conditions are warm (15 to 25°C) and moist during and shortly after bloom. The infection originates on sepals or dying petals and spreads to the calyx end of the fruit. The disease is most common on Paulared, Delicious, Cortland, Honeycrisp and McIntosh.

Symptoms appear about one month after petal fall on the calyx end of the fruit as a brown/grey discolouration that later develops a red border. The lesion is usually sunken and a corky dry rot develops in the flesh. When in storage, calyx end rot can lead to moldy core. 

The disease should not be confused with dry eye rot that is caused by Botrytis cineria from an infection that occurs later in the season. If you typically see symptoms, contact me if you would like to confirm the organism through lab testing.

Recommendations:

  • If calyx/blossom end rot has been an issue in the past, consider using a captan product during full bloom. Infections can occur in problem blocks as the pathogen can last in the soil for several years.
  • If applying Streptomycin with Agral 90 there is a risk of burn if using captan. Prioritize fire blight over blossom end rot.
  • Keeping grass and dandelions mowed will allow the soil to dry and reduce the environmental conditions for spore ejection. Other broadleaf weeds are also a host of this disease so weed control prevents the build up of this pathogen.



Insects


European Red Mite

A delayed dormant oil is effective at managing European red mite if monitoring indicates a treatable overwintering egg population. The oil is most effective when applied around egg hatch (typically around tight cluster and before pink). As of this morning, Erika Bent, APM, reports that egg hatch has not yet begun in the Valley. Hatch is expected to begin soon so the opportunity to apply oil will soon close. However, frost was observed this morning so avoid oil for the next two days.

European red mite eggs overwinter in the cracks on buds and spurs so adequate water volume is needed to reach all of the crevices. The oil treatment is not effective for rust mite or two-spotted spider mite.

Avoid oil if freezing temperatures will occur within 48 hrs and no captan within 7-14 days. Oil should not be applied to young trees at less than 3 years old, and the risk on varieties with Delicious parentage (Ambrosia, Gala) increases after tight cluster.


Nematode (pre-plant samples)

Root and soil samples are best collected in the spring (May-June) or during the fall (September-October), both of which avoid the heat or drought conditions in summer. Soil temperatures at sampling should be above 10°C for adequate nematode presence in the upper soil levels. Samples can be processed by the Agriculture and Food Laboratory (AFL) in Guelph, ON.


Looking Ahead to Pre-Bloom Insecticides

Depending on the heat in the forecast, your region, and monitoring reports, action may be needed soon during the pink stage.

Spring Caterpillar Complex

(winter moth, green pug moth, eyespotted bud moth, speckled green fruitworm, obliquebanded leafroller)

Recommendations:

  • Treatments for spring caterpillars should not be applied too early because product must enter the developing flower clusters where the larvae like to feed to be effective. Treatments should be applied pre-bloom so target the pink stage. 
  • Evidence of feeding includes tiny holes in new leaves and flower buds, and black specks of frass. Begin scouting procedures described in Perennia’s Best Management Practices. Monitor your scouting reports for notes on WM, GPM, and other caterpillars for those with scouting services.
  • Note that there is a lower tolerance for WM than GPM. Green Pug Moth do not feed directly on developing fruitlets.

European Apple Sawfly

Recommendations:

  • Last year there were high catches of EAS in the Valley.
  • In orchards with a history of damage and high numbers of EAS catches, an application of Altacor, Assail, Calypso, or Exirel at full pink is recommended to control the adults prior to egg laying.

Tarnished Plant Bug

Recommendations:

  • If history of tarnished plant bug damage indicates that pressure is moderate to high, an application of insecticide at pink is warranted. Treatment should be applied before bloom, not after.
  • Pyrethroids (group 3) and the sulfoximine product Closer/Cormoran (group 4), are registered for control.


General Notes

  • Monitor for rosy apple aphid populations that exceed thresholds when aphid stem mothers start producing offspring. Treatment pre-bloom is ideal. Closer works well for aphid control.
  • If treatments for OBLR are required at pink, the treatments will also have some activity on WM and GPM. 
  • If a pyrethroid is applied for tarnished plant bug at pink, it will also have activity on WM and GPM. Similarly, pyrethroids are expected to have some activity on EAS if being applied for other pests.
  • As a reminder, pyrethroids are best used at moderate temperatures (20°C or less) and are harsh on beneficial insects and predator mites. They should only be used where potential losses justify their application.


Weed Management

Studies have shown maintaining weed free strips from bud break to 30-days after full bloom has the greatest impact on tree growth and yield.

Recommendations:

  • This week may be a good opportunity for burndown herbicides if needed. Leaf tissue has dried off for Ignite applications and warm temperatures (>16°C) are expected for efficacy with 2,4-D. 
  • In young plantings, weed control is essential. Local research showed that by year 4, a weedy planting was 39% the trunk cross sectional area of a hoed comparison.


Horticulture


General 

  • If you plan to have tile drainage installed in the near future, talk to your drainage company early because they are booking far in advance. 
  • Remove tree guards because otherwise they can trap moisture and encourage disease. 

Pollination

  • Consider that it is near the time that honeybees should be moved into the orchard for pollination when king flowers open.
  • Bees can become accustomed to wild sources of nectar and may ignore apple blossoms. Mow dandelions to encourage apple blossom foraging. 

Grafting

  • Bark typically slips from pink to bloom but can be checked early if you plan to get a head start.

Mowing

  • Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of pre-bloom insecticide applications.

Pruning

  • Plan ahead and watch re-entry intervals for pruning activities.
  • Ensure that youngest blocks are pruned first to ensure growth is directed into desirable leader and terminal extension. Prioritize high value trees and then return to low value areas.
  • Mature blocks are best when pruned prior to bloom to avoid weakening trees.

Fertilizing

  • Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth.
  • Target 10-16 inches of new growth each year. More is a sign of excessive nitrogen.
  • Foliar nutrients to correct nutrient deficiencies:
    • Boron: Applied pre-pink. Do not use water soluble pesticide bags in a tank mix with boron and rinse the tank well before and after boron. Do not use boron with oil or Epsom salts.
    • Magnesium: Epsom salts are applied starting at pink. Do not use with oil or boron.
    • Nitrogen: Urea may be used from pre-pink to mid-June as a nitrogen supplement. Sprays near bloom give a boost of nitrogen when it is needed most. Urea used from tight cluster to mid-July can remedy a nitrogen shortage.
    • When foliar nutrients are applied in slow drying conditions, about 40% is absorbed in 6 hours. When applied in dry conditions, about 75% can be lost in 48 hours. Foliar nutrients are not well-absorbed at below 10°C.

Liming

  • Lime especially if a site is being planted this year. When applied in spring the lime works best when applied as soon as possible to get the product working in the top layer of soil. 
  • Surface applied lime will take a number of years to adjust pH of the soil profile so it is best to apply annually or biannually where needed. If soil testing for pH, measure during the same time each year (August) as pH can change over the growing season. 
  • The provincial limestone trucking assistance program is open.

Planting

More information was provided in the May 2 newsletter.
  • Remember to document the quality of your nursery trees with pictures and notes. 
  • Avoid letting trees dry out.
  • Bundles of trees sitting in water awaiting planting can asphyxiate, especially in stagnant water and/or warmish water.
  • Tilth should be friable enough to avoid air pockets for good root to soil contact.
  • Keep newly planted trees supplied with water for the first few weeks after planting if dry conditions prevail. Watering-in or rainfall soon after planting can help to fill air gaps.

On-Farm Nursery

  • Incorporate lime for nursery plantings rather than surface applications that will take years to take effect.
  • 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


NSFGA Growing Good Growers

  • The Nova Scotia Fruit Growers Association has been offering education sessions to their grower members. This Friday there is a session on blossom and fruitlet thinning. Members can contact Emily Lutz for more information.

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. 
  • The Season Extension Enhancement program is meant to help support fruit and vegetable growers who invest in innovative technologies to extend their growing season, adapt to a changing climate and open up new market opportunities. For more information, visit Horticulture Nova Scotia. 


Pesticide Training Opportunities by Marbicon

Marbicon Inc (Jim Jotcham) has been announced Pesticide Training Opportunities. Pre-exam courses (with 5.0 points available for T2237):

Pre-exam courses (with 5.0 points available for T2237):
May 23 - Berwick Legion in Berwick
June 8 - Truro Horsemen’s Club in Bible Hill

Points workshop (with 5.0 points available for T2236):
June 9 - Truro / Douglas Street Rec Centre, limited seating!
This workshop is not preparation for the provincial applicator exam.

Email/call Jim ( marbicon@eastlink.ca ) or 902-538-7101 to pre-register. Contact Jim if you would like a course near you and/or at a more convenient date. Pre-exam courses are $125 including HST.

People sitting in for 5.0 recertification points only pay $110 including HST.
Doors open at 8:30 am. Food & drink on your own. A course manual is provided.


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 Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Dustin MacLean, Jeff Wentzell, Keith Fuller, Joan Hebb, Larry Lutz, Jeff Franklin, Bob Prange, Suzanne Blatt, Danny Davison, Karen Burgher, Vicky Levesque, and Shawkat Ali.

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

By Michelle Cortens at May 09, 2023
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