Wow, what a difference a warm week makes! Trees jumped ahead two growth stages to now show plenty of open blossoms and shoot growth doubled in length. In today's newsletter we discuss the high risk of apple scab for the next wetting event and the risk of fire blight blossom infections in this week's heat. Speaking of fire blight, do not mix Agral 90 oil and captan fungicide; instead, prioritize an antibiotic + Agral 90 as a spreader-sticker so you do not lose the efficacy of your antibiotic. We discuss thinning strategies but encourage you to join the Growing Good Growers tailgate meeting on Wednesday, May 22 at 11 AM. Thanks to the ongoing commitment of the Orchard Outlook Committee members.
Table of Contents:
- 2024 Degree Day Accumulations
- Cumulative Precipitation
- Apple Buds
- Pear and Stone Fruit Buds
- Apple - Scab
- Apple - Powdery Mildew
- Fire Blight Prevention
- Apple and Pear - Fire Blight Blossom Blight
- Fire Blight - Shoot Blight Management
- Apple - Calyx/Blossom End Rot
- Stone Fruit - Brown Rot
- Do not spray insecticides during bloom!
- Post-Bloom Insecticides for apple, stone fruit, and pear (Advance notice)
- Apple Blossom Thinning
- Apple Fruitlet Thinning
- Pear Fruitlet Thinning
- Pollination
- Grafting
- Mowing
- Weed Management
- Pruning and Training
- Fertilizing
- Nursery Trees
- Planting Trees
- Wild Apple Trees
- Growing Good Growers Tailgate Session about Thinning May 22
Weather
2024 Degree Day Accumulations
With the recent warm temperatures, the degree day accumulations beginning on March 1 for base 5°C plant development are now slightly more than the 5- and 10-year averages (Figure 1). The base 10°C accumulations for insect development are now between the 5- and 10-year averages.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 20 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
- Approximately 6% more plant development heat units compared to the 5-year average, and 2% more compared to the 10-year average.
- Approximately 8% more plant development heat units compared to 2023, and 11% less compared with 2022.
- Approximately 6% more insect development heat units compared to the 5-year average, and 9% less compared to the 10-year average.
Cumulative Precipitation
Figure 2: Both rainfall and the rainfall equivalent from snow at the Kentville Research Station from 2019 to 2024. Provided by Jeff Franklin (AAFC).
Bud Development
Apple Buds
An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on May 20, the Idared buds were at about 70% bloom, Honeycrisp was at full pink and Ambrosia was at pink (Figure 3). In Pereaux the stages are similar with Gravenstein at 70% bloom and Cortland beginning bloom. Over the last week, fruit buds jumped ahead by two growth stages (last week was tight cluster/bud separation!).If you want to target the early timing for Apogee/Kudos of 2.5 cm, note that by the pink stage the vegetative growth is at about 3 cm and is adequate for application (Figure 4). Over the last week, shoot growth doubled in length!
Figure 3: Fruit bud development in an early region on Middle Dyke Road in Kentville on May 20. Shown from left to right: Idared (70% bloom), Honeycrisp (full pink), and Ambrosia (pink).
Figure 4: Vegetative bud development in an early region on Middle Dyke Road in Kentville on May 20. Shown from left to right: Idared (5 cm), Honeycrisp (3 cm), and Ambrosia (3 cm).
Pear and Stone Fruit Buds
Figure 5: Bud development in an early region in Greenwich on May 20. Shown from left to right: pear (full bloom), peach (full bloom to petal fall), and European plum (full bloom).
Figure 6: Peach buds circled in red are likely a result of weak bud set after the polar vortex in Feb 2023.
Diseases
Apple – Scab
A handful of regions near the south mountain saw scattered showers on Thursday, May 16. Those regions that received rainfall would have had an ascospore release of 27.5% and would have needed about 10 hours of wetness for an infection to occur as shown in the Modified Mills Table. This situation does not represent most regions in the Valley.
Recommendations:
- Most of the Valley that has not received rain since May 8-10 is in the following situation:
- The total seasonal ascospore load is mature to 75.5% with 56.4% of the spore load available since the last release (as of today).
- Ascospores will continue maturing at a rate of 5-6% per day.
- Over the last week, shoot growth doubled in length and fruit buds jumped ahead by two growth stages. There is plenty of new tissue!
- Be warned that the next apple scab infection event is going to release a very large spore load. Also, in warm temperatures the risk of infection is highly likely given rain. Post-infection control is not encouraged and especially not for the next infection event.
- Let's review some considerations for product options at this time of the year.
- Mancozeb (Manzate/Penncozeb) can be used only 4 times/year. Mancozeb is compatible with oil and may be used around the same time as streptomycin/kasumin + Agral 90 or it may be used as the spreader-sticker. If it is necessary to include mancozeb with your antibiotic, reduce your rate of Agral 90 by at least half to avoid strep burn.
- Captan is not recommended for application with an antibiotic. Firstly, Captan is not compatible with oil so it CANNOT be combined with Agral 90. Secondly, Captan does not act as a spreader-sticker so using it with your antibiotic would sacrifice coverage and efficacy which is not recommended.
- Allegro may be applied as long as oil has not been applied within 3 days (including Fontelis and Agral 90). The REI is short at 24 hrs.
- Do not apply: Folpan/Follow and Syllit should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
- Buran is registered for scab suppression only and must be applied post-infection so it is not recommended for the next event that will be high-risk.
- Note that single site products in group 3 are not expected to provide control of apple scab due to resistance. For other single site products, check the label for rates required for apple scab control because for Luna Tranquility the high rate is needed unless it is tank mixed with another product for scab control.
- Apply a protectant fungicide to green tissue prior to an infection event and reapply on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
- 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:
- A second application of a mildew protectant is usually used before bloom but there might not have been time this year. If that is the case, the petal fall timing is another opportunity.
- If you're using Luna Tranquility for powdery mildew, concurrent activity for scab control is only provided at the high rate. If you're using a full rate of Nova, Fullback or Cevya, no scab activity is expected due to resistance. If using Nova, the water soluble packaging should not be mixed with oil or boron.
- 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.
- Buran is registered for control of powdery mildew in apples under low to moderate disease pressure and local research is ongoing. Apply with 0.1% Agral 90. This product does not have protectant scab activity so will only provide scab protection post-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.
Fire Blight Prevention
Recommendations:
- Cankers are certainly active now and ooze has been confirmed.
- 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.
- Do not pinch flowers this week because temperatures are warm and conducive to bacterial growth. Pinching may be done on young trees if blossoms are not yet open as long as tissues are dry. Any remaining flowers are susceptible to infection.
Apple and Pear – Fire Blight Blossom Blight
Monitoring for Blossom Blight
Ideally you will monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers. Subscribe or renew your subscription here: https://farmdatatools.ca/services/pomeblight/. Then enter your activation code at www.app.farmdatatools.ca in the business settings under 'set up'. Contact me if you need a quick refresher or need help setting up. Run the model using your own temperature, rainfall, bloom and spray dates (industry alerts will offer limited scenarios).
Current and Forecast Blossom Blight Risk
- The most recent email alert was sent this morning.
- ALL regions are currently forecast to exceed the EIP threshold of 100 tomorrow on Wednesday, May 22. If wetting occurs an infection is expected.
- Unfortunately, it is not easy to predict a dew. Whether a dew occurs is related to soil moisture and the dewpoint temperature. However, do not underestimate dew. The even wetting of surfaces is very conducive to bacterial movement down the flower. If you are planning to use Kasumin, it must be applied prior to wetting/dew so you would have to assume that dew would happen. Kasumin is also best applied in the evening because it degrades in UV light.
- Do not spray high water volumes on trees in bloom for most of this week unless an antibiotic has been applied and you know that your EIP level is safe.
- An antibiotic applied on Tuesday or Wednesday is expected to provide protection on the day of application and for one day afterward. Then new unprotected flowers will open and bacterial populations are expected to become high again. According to the forecast, the EIP will remain high for most of this week.
- If choosing to apply an antibiotic today, I would recommend waiting until evening after today's flowers open so that today's flowers receive antibiotic protection. An antibiotic is not necessary on Tuesday but it would reduce bacteria for Wednesday. Alternatively, the antibiotic may be applied on Wednesday. Wednesday may be preferable because plenty of bacterial growth will occur in Wednesday's heat. This year has been very situation-dependent so if you are unclear I recommend you reach out to me or your consultant for support.
Fire Blight - Shoot Blight Management
Recommendations:
- Apogee/Kudos (prohexadione calcium) supress shoot blight. Their use is highly recommended this year because there is a high risk of fire blight infection during full bloom.
- The timing of the first application at 2.5-7.5 cm of new shoot growth is critical to success. Follow up with a second application applied around 14 days later. The products slow fire blight movement in the tree to buy time for removing infections and also reduce the incidence of canker formation. The product becomes effective about 10 days after application so for maximum prevention of fire blight damage apply it early and before symptoms of infection appear.
- Apogee should be put on with higher water volumes to cover all new leaves and growing tips.
- Include Agral 90 at 500 mL per 1000 L of water. Do not exceed this amount of surfactant. If applying Agral 90 there may be a risk of burn if using Captan.
- Apogee should also be applied with spray grade ammonium sulphate (AMS) in an equal 1:1 ratio with the amount of Apogee used (e.g. 500 g Apogee = 500 g or 0.5 L of ammonium sulphate). This is not the blossom thinning product ammonium thiosulphate (ATS)!
Apple – Calyx/Blossom End Rot
Recommendations:
- The only product with activity on calyx/blossom end rot is captan applied during full bloom. If applying Streptomycin with Agral 90 there is a risk of burn if using captan. Prioritize fire blight over blossom end rot. Blossom end rot might not be treatable this year.
- Infections can occur in problem blocks as the pathogen can last in the soil for several years. The disease is most common on Paulared, Delicious, Cortland, Honeycrisp and McIntosh.
- 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.
Stone Fruit - Brown Rot
- Fungicide protection from brown rot should be maintained during periods of warm and wet weather.
- For plums, the use of Captan/Maestro for brown rot during the white bud stage through fruit set will also give some control of new black knot infections.
- Rotating classes of brown rot fungicides is key to slow resistance development.
Insects
BE RESPONSIBLE FOR POLLINATORS – DO NOT SPRAY INSECTICIDES DURING BLOOM!
- Fungicide, antibiotic, and growth regulator sprays are best applied early morning or late evening when bees are not actively foraging. Be aware that dandelion blooms are open until about dusk.
Apple Insects
In anticipation of upcoming petal fall, pesticide options are listed in the table. Choose insecticides by considering what you are targeting and what the products control. Often your hardest to control pest will determine what you need to use, then check the label of that product for all pests that are also controlled by the product. Please refer to the petal fall insecticide decision table for a quick overview of your choices for apple trees.(Click image to access full size PDF file for printing)
Stone Fruit Insects
Plum curculio is a weevil that begins laying eggs in stone fruit at shuck fall. Mated females will deposit their eggs in the developing fruit leaving the characteristic crescent-shaped scar. Activity of PC is increased in temperatures above 16°C.Recommendations:
- Treatment for PC should be applied at petal fall before shuck split to obtain optimal control. Treat between petal fall and shuck split. A second application is usually needed about 10 days later.
- The insecticides available for managing plum curculio include Malathion, Pounce, Assail (Neonicotinoid) and Exirel (Diamide). The neonicotinoids kill plum curculio on contact, and they are also systemic so they deter egg laying and feeding. Their systemic activity will also kill eggs and larvae that are present in the fruit.
- Plum curculio will target apples if stone fruit are nearby.
- Be aware of bee toxicity warnings on pesticide labels and take precautions while nearby crops are in bloom.
- For stone fruit, monitor for green peach aphids and black cherry aphid.
- Tarnished plant bug and stinging bugs cause catfacing of peaches. This stinging takes place around shuck split/fall and one to two insecticide applications may be required to reduce the incidence of catfacing if pressure is high. Apply one to two applications of one of the pyrethroids listed in the Online Pest Guide for peaches. Repeat treatment in 5-7 days if additional stings are detected. Note that pyrethroids are best used at moderate temperatures (20°C or less) and lose efficacy at around 25°C.
Pear Insects
- If you are planning to use Agri-Mek + Oil for pear psylla control, it is best to apply it at petal fall or ideally within 2 weeks. Agri-Mek has better residual control when applied to younger tissues.
- Do not apply Agri-Mek with any bloom around as this product is highly toxic to bees.
- Do not use Captan/Maestro as a fungicide for pear scab within 14 days of Agri-Mek + Oil.
- Do not use MaxCel in close proximity to AgriMek because the oil will increase thinning activity.
- Minecto Pro (Abamectin and Cyantraniliprole) is a new formulation that is registered for control of pear psylla with the same recommended application time.
- Petal fall is the ideal treatment timing for winter moth and fruit worm in pear. Treatment should be based on need determined by monitoring.
- Apple curculio is difficult to monitor for and its presence often is not observed until damage on fruitlets shows up. Treatments for this pest should go on when pears have reached petal fall. Use of one of the products registered for plum curculio should also control apple curculio.
Thinning
See the Events section for information about the next Growing Good Growers tailgate meeting on the topic of thinning.Apple Blossom Thinning
This year is not looking like a great time to practice blossom thinning for the following reasons:
- There is widespread frost injury to king buds. This is a complication because blossom thinning attempts to thin after the king bud is set to target killing side buds. Without a king bud, the differentiation between side buds is challenging in practice.
- This entire week is forecast to be warm and conducive to rapid fire blight bacterial growth. If ATS is used, an antibiotic is needed prior to ATS.
Apple Fruitlet Thinning
- The optimal temperature for thinner activity is between 21-24°C (within fruit sizes of 5 to 18 mm and most effective from 7-12 mm).
- This year a new thinner called Accede is registered and has activity at up to 25 mm fruitlet diameter. Product supply is limited but you may wish to try it on a small scale.
- Note that the PHI for Sevin is 75 days and this may be challenging for early varieties like Paula Red. The REI is 0.5-17 days depending on the activity.
Recommendations:
- A heavy crop load this year with many lateral buds is going to require an aggressive-enough approach to thinning. A petal fall application period may be an alternative to blossom thinning, even if done for only the upper 90% of the trees.
- Even though the fruit set is unclear at petal fall, the thinning effect is mild as fruitlets are not very sensitive to thinners yet. (As long as temperatures are below 24°C.)
- The petal fall timing (5-6 mm) might give you a second chance to thin again a week later if needed when fruit set becomes more clear.
- The products that are effective at petal fall include Sevin and Fruitone unless we get the heat needed for MaxCel/Cilis Plus.
- Local studies show that conservative petal fall treatments did not improve fruit quality but that more aggressive treatments did. Although the conservative treatments like Fruitone alone, MaxCel alone, and Sevin alone did not improve fruit quality, they did generally reduce fruit set.
- If you use Sevin at the petal fall timing then do not exceed the yearly rate of 3.22 L/ha in high density plantings or 2.15 L/ha/year in low density plantings.
- Also note that Sevin is toxic to bees so it cannot be applied to open blossoms.
- At thinning time, consider the weather and then adjust your usual rate +/- 20%. I will discuss the weather as thinning time approaches.
- Have a block with trees on and off? Thin according to trees with the heaviest fruit set. Trees with less flowers are less likely to thin anyway because holding onto well-supplied fruitlets.
- Varieties prone to biennial bearing that had a low crop load last year should be thinned adequately and early enough this year to enable bud initiation (for Honeycrisp this is within 45 days after bloom).
- Defruiting young trees can be accomplished with a combination of Sevin XLR at 2.5 L plus Maxcel/Cilis Plus at 5.0 L per 1000 L of water applied using dilute nozzles to the point of drip. A few litres of oil (10.6 L/1000 L water) can also be added as a spreader sticker to this combination unless the variety is sensitive to oil. This mixture should cover more than an acre of young trees. Apply from petal fall until 8-10 mm. A second application can be done before 18 mm if additional thinning is needed. Hand thinning may still be needed.
Pear Fruitlet Thinning
- The Maxcel thinning window is 8-14 mm and early treatments are most effective.
Horticulture
Pollination
- Monitor bee activity to estimate fruit set.
Grafting
- Bark typically slips from pink to bloom.
Mowing
- Keeping the orchard floor cover mowed to minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.
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. Timely herbicide application will ensure you make the most of the weed free window.
- 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.
- 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. Trees planted this year before May 8 would have received a good settling rain and you may consider a residual herbicide before the next rain.
- 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.
Pruning and Training
- Plan ahead and watch re-entry intervals for pruning activities.
- Trees are best when pruned prior to bloom unless you wish to reduce vigour.
- A handout for farm workers 'The Fundamentals of Pruning' was published this year.
- Ensure that deer fencing is installed as soon as possible to protect new growth on young trees.
- 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).
Fertilizing
- Bearing apple trees need about 0 to 60 kg of actual nitrogen/ha/year banded into the tree row. Triple 17 contains 17% actual nitrogen and ammonium nitrate contains 33-35% actual nitrogen. Nonbearing trees may receive some more nitrogen before the end of June.
- Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth. However, there is not much rain in the forecast so granules may still be on the surface. 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.
- Target 10-16 inches of new growth on bearing trees each year. More growth 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. Do not apply Epsom salt to trees with a tendency to have bitter pit because the magnesium will out-compete the calcium and aggravate bitter pit.
Nursery Trees
- The ground received a good settling rain and you may consider a residual herbicide before the next rain.
Planting Trees
- A new report has been published by Perennia to summarize local research on, "Developing knowledge-based strategies to manage plant parasitic nematodes in Nova Scotia apple orchards."
- Remember to document the quality of purchased nursery trees with pictures and notes. Did trees dry out? Any signs of disease (cankers, crown gall)? How do the roots look (rinse and take a photo)? Notify the appropriate people of issues you notice. Record the date of planting. An issue that shows up after planting is much easier to diagnose or prevent given this information.
- Avoid letting trees dry out. About 40% of trees can die from drying out, and surviving trees grow slowly. Survivors of 15-minute dry winds recover by year 3. Survivors of 45-minute drying winds still don't grow well by year 3.
- Bundles of trees sitting in water awaiting planting can asphyxiate, especially in stagnant water and/or warmish water.
- The length of the rootstock that is above ground level will influence tree growth. Tree size diminishes as the rootstock portion above ground increases. Trees should be planted so that the graft unions are at a uniform height of 8 to 10 cm above the soil line.
- Wait for a settling rain before applying a residual herbicide to young plantings.
- Consider painting the trunks of newly planted trees white to prevent herbicide injury. Use a water-based white latex paint that may be diluted 50% with water.
Wild Apple Trees
- Wild apple trees harbour pests, in particular apple maggot, that can then spread to nearby orchards. Now that wild apple trees are in bloom, it’s a good time to flag trees on your own property so that you can find them later in the season for removal.
Events and Notices
Growing Good Growers Tailgate Session about Thinning May 22
We hope that you can join us for the next Growing Good Growers tailgate session hosted by NSFGA and Perennia. These pop-up sessions are meant to offer the space to discuss questions during the season and will offer learning opportunities from one another.The Growing Good Growers tailgate session will be held at Birchleigh Farms on Wednesday, May 22 @ 11 am. The topic is blossom and fruitlet thinning. Have you blossom thinned or are you interested in trying it? Is blossom thinning a safe approach after freeze injury to king fruitlets? Then thinking further ahead to fruitlet thinning there are three key timings at petal fall, small fruitlets, and rescue timing. What has been your experience with timings and products? Michelle will share some local experience with Accede with this being the first season that it is registered. Please bring your thoughts, experiences, and questions on thinning and join us for this discussion.
Please meet us at 4492 Highway 1 in South Berwick on the south side of highway 1 by the building. There is a Honeycrisp orchard with plenty of buds.
There is no need to RVSP, and we encourage you to bring your own coffee and snacks. Everyone is welcome to attend!
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: Harrison Wright, Danny Davison, Keith Fuller, Jeff Franklin, Shawkat Ali, Jill MacDonald, Joan Hebb, Larry Lutz, Suzanne Blatt, and Jessica D'Entremont.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
