Orchard Outlook Newsletter Vol. 22, No 13

In today's newsletter, note that degree days up until now are running very close to average. As time goes on there are more reports of trees succumbing to winter injury but usually they had an underlying weakness and could not withstand cold temperatures. For disease management, note the prevalence of fire blight infections and the benefits of aggressive pruning. For insects, apple maggot has not yet been captured by Dr. Suzanne Blatt's team in Kentville. Watch out for re-entry intervals on products for hand thinning trees and long pre harvest intervals for certain products.

Table of Contents:

Weather

• 2022 Degree Day Accumulations
• Apple Tree Health

Diseases

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

Insects

• Apple Insects
• Stone Fruit Insects
• Pear Insects

Horticulture

• Summer Hedging
• Solstice Reminders
• Calcium Nutrition
• Weed Management
• Mowing
• Training
• Young Trees
• On-farm Nursery

Pest Management Guides 2022

Events and Notices

• New Book: Controlled Atmosphere Storage of Apples and Pears
• NSFGA Orchard Tour (save the date)
• On-Farm Climate Action Fund for Nova Scotia and Newfoundland and Labrador is Open

Weather

2022 Degree Day Accumulations

The cumulative degree days are very close to the 5 and 10-year averages for base 5°C and 10°C heat units (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% more plant development heat units compared to the 5-year average, and 4% more compared to the 10-year average.
• Approximately 7% less plant development heat units compared to 2021, and 5% more compared with 2020.
• Approximately 3% more insect development heat units compared to the 5-year average, and 2% more compared to the 10-year average.

Apple Tree Health

Tree death appears to be more common this year and is likely related to stressful winter temperatures. In most cases the tree death is happening where trees were already in a weakened state from underlying issues. The pressure from cold temperatures preyed on weakened trees and singled them out in blocks by causing them to collapse. 

Southwest tree injury is a form of winter injury that can be confused for phytophthora because it produces a zone of dead tissue near the graft union, so let me know if you would like a second opinion.

Diseases

Apple – Scab

Recommendations:

• Do not reduce fungicide spray intervals until you can identify your pressure from scab lesions. Wait until at least 2 weeks after the last primary infection event that was theoretically on June 13. Also note the risk of summer diseases if spray programs are stretched to the limit.
• 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.
• Folpet (Folpan) cautions
• Do not use folpan until 30 days after petal fall to avoid fruit russeting, especially on sensitive varieties.
• Also note that new to this year Folpan has a 6-day REI for hand thinning fruit.
• 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. 
• The pre-harvest interval for EBDC fungicides (e.g. Manzate, Dithane) for fruit destined for the United States is 77 days versus 45 days for the domestic market. An application of EBDC on July 5 would require until September 20 to meet pre-harvest requirements for the United States.
• Always tank mix single site fungicides with a group M for resistance management.
• 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. Carefully review nutrient formulations that might contain boron in small quantities.

Apple – Powdery Mildew

Recommendations:

• Powdery mildew will continue to spread until terminal bud set. Remember that late summer sprays are protectants for new tissue and they are not eradicants on previously infected tissue.
• Powdery mildew protection should go on prior to a period of warm and dry weather when infections are expected, and not prior to heavy rain. 
• Do not apply more than two consecutive applications of a group 3 or group 7 fungicide.
• Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.

Fire Blight - Orchard Management

If you are noticing fire blight pressure this year you are not alone. There were several infection events with EIP above 100 during full bloom that coincided with rainfall. Festering infections from last year offered plenty of bacteria to cause blossom infections where protection was not adequate. Maybe antibiotics were applied to only every second row and coverage didn't reach the floral stigma of susceptible varieties that were protected by fluffy petals, and maybe full control wasn't achieved by post-infection treatment. 

Recommendations:

• Monitoring: 
• Continue monitoring for signs of blossom infection, especially in young blocks. Monitor for shoot blight on suckers that can infect the rootstock.
• Pruning:
• In the case of a manageable amount of infections, timely and frequent pruning of active infections can slow the spread and minimize losses of entire trees. 
• Remove fire blight strikes at least 2-4 ft below active infections to remove the leading edge of the bacteria. Being aggressive at the first sign of symptoms will help prevent the re-occurrence of symptoms and the need for continuous cutting back.
• Research by Clarke 1991 shows that when infected shoots are pruned at only the base of visible symptoms, in 57% of cases the infections continue unimpaired. Pruning at least 0.6 ft allows infections to continue in 12% of cases. 
• Pruning back to at least 2 year old wood is more resistant to infection.
• If possible, leave a 4 inch stub at a branch union so that a canker would form on the stub rather than on the leader. Cankers are likely to form on the stub so they should be marked (spray paint) for removal during winter pruning.
• 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. 
• Slowing:
• If a blossom blight infection occurred, prohexadione calcium is a tool known to slow down bacterial spread in the tree and may buy some time before bacteria reach the leader.

Apple – Black Rot

• 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. 
• There are few management options to cover such a long risk period. Merivon has activity but group 7 + 11 products should not be used more than 4 times each year. 
• Fungicides are protectants because they prevent spore germination on plant tissues so for protection from this disease the fungicides would need to be applied prior to the wetting event. 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.
• Check for nearby brush or wood piles because they serve as a major source of inoculum. Remove the brush pile to reduce the chance of infection.
• Frog eye leaf spot infections on leaves tell you that you have black rot inoculum present. Oftentimes, the frog eye leaf spot will be in close proximity to fruitlet mummies.

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, Allegro, Pristine, and Merivon (or Folpan 30 days after petal fall).

Insects

Apple Insects

• Aphids: Asses trees for active rosy apple aphid colonies before determining the need to treat for this insect. Monitor for green aphid. In young trees the aphids can disrupt shoot growth. Monitor nursery plantings as well. Now that leaves are curling 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.

• Codling moth:

• If trap captures are below the treatment threshold but continue to build over time then treatment should be applied once a threshold is reached. 
• A heavy rain just after application is more concerning than a late application because heavy rain would wash off and reduce the residual life of the insecticide. 
• Approximately a week after application of an OP insecticide, 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.

• 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.
• 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.

• 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. No captures have been noted yet for this year by Dr. Suzanne Blatt's team at the research station.
• 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.

Stone Fruit Insects

• Mites and aphids: Monitor mite and aphid populations. Prolonged feeding especially in early- to mid-summer can affect next year’s fruit set.

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 degree day timing given for apples.

Horticulture

Summer Hedging

• A study by Perennia in 2013 evaluated the regrowth on summer hedging using Ambrosia on M.9 and Gala. Treatments were applied at 6, 8, and 10-leaves of new growth corresponding to June 25, July 5, and July 11, respectively. 
• Table 1. Summary of regrowth from summer hedging cuts to ‘Ambrosia’ and ‘Gala’ apple trees in the Annapolis Valley.

• Cultivar	Frequency of Regrowth (%)			Length of Regrowth (cm)
  	25 June	5 July	11 July	25 June	5 July	11 July
  Ambrosia	100	100	90	6.4	3.6	2.2
  Gala	100	100	80	21.4	12.3	3.1

• Regrowth occurred most frequently on cuts to the current year’s growth, and hedging cuts into 1-year-old and older wood also often generated regrowth. 
• Note that more vigorous rootstocks would be expected to have greater re-growth response.
• For more information, there is a good article from Cornell that concludes: first week of June hedging = 8 inches regrowth with a terminal flower bud, first week of July = 5 inches regrowth, and first week of August = no regrowth. Note that in the Cornell study they evaluated M.9 with several varieties.

Solstice Reminders

• If granular fertilizer is applied now, the risk is that any dry weather in July will slow the release. Late release will prevent trees from hardening off before the winter. Top dressing is not recommended after the end of June.
• 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.

Calcium Nutrition

• Note that nutrient product formulations with calcium may contain boron that would interact poorly with water soluble packaging.
• The goal of foliar Ca sprays is to increase the concentration of Ca in the fruit and reduce bitter bit incidence. 
• As fruit grow and increase in surface area, a greater total amount of the calcium applied is taken up by the fruit. If bitter pit has not been a significant issue, then begin calcium applications at 4 to 6 weeks after petal fall.
• Calcium applied at two-week intervals is better than occasional, high-rate applications. 
• The recommended rate is 4 to 14 pounds of elemental calcium per acre in a season spread over six to eight cover sprays. The percentage of elemental calcium will be listed on the label.
• 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.
• Calcium chloride flake (77% Ca) is the most economical Ca material to use but also the highest risk for foliar burn. Apply calcium chloride flake at no more than 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.

Weed Management

• Note that 2,4-D has an 80-day PHI.
• Prevent herbicide drift by avoiding sprays during wind gusts, periods of dead calm, wind speeds above 16 km/hr, and temperatures above 25°C.
• Due to herbicide shortages, it seems that weed management in young plantings will be reliant on consistent and vigilant use of burnoff products. Note the risk of frequent use of Agral 90 for bark blistering on Delicious varieties.
• Be cautious when applying post-emergent herbicides to prevent injury to young trees.

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

Training

• Select strong terminals on young trees and remove competing terminals to single the tops.
• 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.
• 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). This year is expected to be an active hurricane season.

Young Trees

• 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.
• 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.
• 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.

On-Farm Nursery

• Monitor for aphids and leafhoppers.
• 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!
• Although Aim is registered for use in nurseries, damage has been reported several times in the past. It is a contact herbicide so it kills tissue on contact.

Pest Management Guides 2022

All changes new to 2022 are made in red text directly on the guides. The information on all changes was summarized in a blog post on April 8th.

• Download the 2022 Pome Fruit Management Guide
• Download the 2022 Organic Apple Management Guide
• Download the 2022 Stone Fruit Management Guide
• Download the 2022 Thinners and Growth Regulators Guide
• Download the 2022 Tree Fruit Weed Management Guide

Events and Notices

For upcoming events, visit the ‘Events’ tab on the NS Tree Fruit Blog. Specific events will be described here when available.

New Book: Controlled Atmosphere Storage of Apple and Pears

Dr. Robert Prange has informed me that his new book is available. The intent of the publication is to update Kupferman’s CA storage recommendations with more recent data, including information on storage temperature, O2, and CO2. In addition, chapters have been added on storage humidity, use of postharvest chemicals such as diphenylamine (DPA), ethoxyquin, 1-methylcyclopropene (1-MCP) and aminovinylglycine (AVG), CA and dynamic controlled atmosphere (DCA) history and harvest and storage protocols. The book is $120 CAD PLUS shipping and handling (includes a free copy of the 1994 Postharvest disorders of apples and pears. AAFC Bulletin 1737, 67 p., while supplies last). Contact prangepublications@gmail.com for further information.

NSFGA Orchard Tour (save the date)

The Production Committee has set the date of the 2022 Orchard Tour as August 11th. This date is later than usual so please mark your calendars. Further details will be released as the tour is finalized.

On-Farm Climate Action Fund for Nova Scotia and Newfoundland and Labrador is Open

A new funding program will help farmers receive up to $75,000 in funding when adopting and implementing beneficial management practices (BMPs) that store carbon and reduce greenhouse gases, specifically in the areas of: 

• Improved nitrogen management 
• Cover cropping, and 
• Rotational grazing 

The On-Farm Climate Action Fund (OFCAF) is part of the Government of Canada's Agricultural Climate Solutions, a multi-stream program to help farmers tackle climate change. Perennia Food and Agriculture Inc. is implementing the fund to help farmers adopt these practices in Nova Scotia and in Newfoundland and Labrador. Training for farmers and agronomists will also be offered over the two-year program, which ends in March 2024. For more information on the program or to apply please visit the website ofcaf.perennia.ca. Deadline for the first intake of applications is July 31, 2022.

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