Today's newsletter reports average king fruitlet diameters on varieties ranging from 10.1 mm to 16.7 mm so the window of opportunity for chemical thinning will soon come to a close. Keep an eye on the heat this week because the forecast is currently showing the possibility of 29°C which is the danger zone that can result in overthinning at high enough rates of chemical thinners. Otherwise, the warm temperatures early this week are expected to be good for activity of MaxCel/Cilis Plus used on small-fruited varieties like Gala and for defruiting young trees. More thoughts on chemical thinning are discussed as well as initial thoughts on why we are seeing lower-than-expected fruit set in some situations. Please be aware of the week-long risk of fire blight infections on open blossoms in young trees so you can develop a strategy. Thanks to the ongoing commitment of the Orchard Outlook Committee members.
Table of Contents:
- 2024 Degree Day Accumulations
- Apple Buds
- Thoughts on Fruit Set
- Pear and Stone Fruit Buds
- Apple - Scab
- Apple - Powdery Mildew
- Fire Blight Prevention
- Apple - Fire Blight Blossom Blight
- Fire Blight - Shoot Blight Management
- Apple - Black Rot
- Apple Insects
- Apple and Pear - Codling Moth
- Apple Fruitlet Thinning
- Defruiting Young Trees
- Pear Fruitlet Thinning
- Peach Hand Thinning
- Cover Crops
- Mowing
- Weed Management
- Pruning and Training
- Nursery Trees
- Save the Date - NSFGA Summer Tour August 7
- Perennia Webinars: Understanding Alternative Nutrient Amendment
- 2024 Virtual Orchard Meetups Series
Weather
2024 Degree Day Accumulations
The degree day accumulations for base 5°C plant development and base 10°C insect development are still slightly more than the 5- and 10-year averages (Figure 1).
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to June 9 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
- Approximately 13% more plant development heat units compared to the 5-year average, and 12% more compared to the 10-year average.
- Approximately 25% more plant development heat units compared to 2023, and equal to 2022.
- Approximately 18% more insect development heat units compared to the 5-year average, and 14% more compared to the 10-year average.
Bud Development
Apple Buds
An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on June 10, ten king fruitlets of each of the following varieties were measured to get a rough average (size of side fruitlets is irrelevant). The Idared measured 16.7 mm (grew 1 mm/day), Honeycrisp 12.0 mm (grew 0.7 mm/day), and Ambrosia 10.1 mm (grew 0.6 mm/day) (Figure 2).Early varieties have surpassed the thinning window of opportunity. Later varieties are still within the thinning window but action should be taken soon. Refer to the thinning section later in the newsletter for more information.
Figure 2: Fruit bud development in an early region on Middle Dyke Road in Kentville on June 10. Shown from left to right: Idared (16.7 mm), Honeycrisp (12.0 mm), and Ambrosia (10.1 mm). The king fruitlet is measured to represent fruit stage for thinning and the size of the side fruitlets is irrelevant.
Thoughts on Fruit Set
Although pollination weather appeared to be excellent, not all fruit have set. Honeycrip is one of the affected varieties and the phenomenon appears widespread. However, before assuming that you do not have much fruit please get out of the truck and count the fruitlets up-close on an entire tree, fingering through the fruitlets rather than just estimating by eye. Certainly the Honeycrisp did not set as strong as expected but in most cases there should be enough for a good crop or even too much. Trees need to set only about 5% of flowers for a commercial crop.
There are many theories as to why fruit set was lower than expected that have been considered. Some theories will be explored further where possible:
Leading theory: Fewer bees during bloom?
- “Seemed like” fewer bees this year from field observations in orchards and other crops.
- There is evidence from researchers at AAFC that native bee numbers were extremely low this spring, specifically bumblebee populations due to fewer overwintered queens. This appears to be the case in agricultural and non-agricultural sites. Spring bumblebee numbers can be low in a few rare years.
- Compounding this problem of low pollinator populations, the bee boxes in orchards were moved to wild blueberry before full bloom. The apple and wild blueberry crops had synchronous bloom periods causing the bee boxes to be moved out early. To avoid this issue in the future, plan for bees and nearby pollinator varieties.
- We are curious to know how fruit set fared in solid Honeycrisp blocks versus blocks with pollinator varieties.
- We are also curious to compare orchards that had bee boxes throughout the entire bloom period versus those that did not.
- It is clear when flowers were aborted because they stopped growing and fell off. We wonder if possibly other buds were mildly damaged but still managed to bloom and were deceptive.
- We would like to map out areas with low fruit set to see if it is related to low temperatures.
Theory: Stress from snowball bloom?
- Some fruit drop due to the stress from competing flowers is possible. Are we seeing fruit set that relates to the biennial bearing tendencies of individual trees - making snowball bloom erratic throughout a block?
- Other regions say that dry seasons lead to poor fruit set the following year. Last year was was dry and then wet.
- Due to the rain and cloud cover in 2023, there was less sunlight than usual and perhaps also less production of carbohydrates.
- Heavy rain might also have leached more nitrogen than usual.
- We question if fruit buds were weak. However, regardless of all of these possible scenarios the flowers were developed and appeared healthy at the start of bloom in 2024.
Unlikely Theory: Too hot midday during bloom?
- Bloom was abnormally hot for Nova Scotia but not excessively hot. This theory is unlikely because warmer regions grow Honeycrisp successfully.
- Honeycrisp in particular should be winter hardy. Dr. Willick says injury to apple buds was minimal from the polar vortex. In 2024 he observed greater early and mid winter hardiness in 2024 buds. There do not appear to be legacy effects from the polar vortex.
Pear and Stone Fruit Buds
Figure 3: Bud development in an early region in Greenwich on June 10. Shown from left to right: pear (13.5 mm), peach (2.0 cm), and European plum (2.0 cm).
Diseases
Apple – Scab
Table 1: Apple scab infection events in Kentville from June 5 to June 11, 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.
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.
Recommendations:
- According to the model, total seasonal ascospores matured to 100% on Saturday, June 8 and then a wetting event on June 9 would have released the final primary spores. Models are not completely accurate so wait 2 weeks after ascospores are depleted and when you can assess your incidence of primary apple scab infections. But there is now a light at the end of the tunnel!
- Let's revisit some considerations for product options at this time of the year:
- Captan may be used as long as it is not applied within 7-14 days of an oil such as Agral 90 (worse if applied after oil that preconditions leaves). The REI for hand thinning fruit in high-density systems is 15 days and in low-density systems it is 24 days. The product has activity on summer diseases. For high density, do not use more than 10 applications per year and for low density do not use more than 2 applications per year. Remember, if using SHARDA CAPTAN 48 the rate equivalent to other captan products is 5 L/ha (2.4 kg of active ingredient). Please note that this liquid format might improve uptake and also increase the risk of leaf injury.
- 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 may be considered again. But remember that the product is registered for only suppression of apple scab and must be used post-infection only. Summer disease control is not likely strong.
- 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.
- Several of the single site products do not have activity on scab after petal fall (fruit scab). Such products include Fullback, Nova, Cevya, Aprovia, Sercadis, Excalia, Scala, and Vangard.
- 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:
- Protection may continue for 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.
- The forecast of warm and rain-free periods would suggest that this week offers the opportunity for infections to happen.
- 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.
Fire Blight Prevention
Recommendations:
- Pruning and training 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.
- Even if bacterial EIP populations are low, do not pinch flowers in wet weather. Pinching causes open wounds like a trauma event and bacteria are transported to wounds in wet weather. Remember that any remaining flowers are susceptible to infection if the EIP becomes high.
Apple and Pear – Fire Blight Blossom Blight
Current and Forecast Blossom Blight Risk
- Industry alerts will continue while rattail bloom and bloom in young plantings is present.
- An alert was sent this morning for risk of infection today. As stated in the alert, most regions are forecast to exceed the EIP threshold of 100 on open blossoms today on Tuesday, June 11. If wetting occurs an infection is expected.
- An antibiotic is forecast to provide protection on the day of application and for one day afterward. In the heat, new flowers open and bacteria grow quickly. Phone me for more details.
- EIP values are expected to be high for the entire week.
- Ideally you can monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers.
Recommendations:
- Do not underestimate the risk of infections on late flowers. By the time of late flowers there is already plenty of bacteria established throughout the environment.
- How many blooms per tree is a concern for fire blight? Consider that one blossom per tree is one potential infection per tree. One infection is enough to kill a tree so one infection per tree is too many infections.
- Have a strategy for a week-long risk of infections. You may pinch the flowers on dry days or rely on an antibiotic. If possible, use Kasumin during bloom when conditions allow in order to save streptomycin applications for less-flexible risk periods.
Fire Blight - Shoot Blight Management
Recommendations:
- If you applied Apogee/Kudos, follow up with a second application applied around 14 days later. You may question if you need two applications for fire blight management. I recommend the two applications because the product has activity for three to four weeks following application and then it is degraded by the plant. By the time you notice blossom infections, your first application will have worn off. Successive applications ensure no gap in activity until you can assess infection pressure.
- The industry had high risk of infection during the full bloom period so any efforts to proactively slow fire blight infections will be worthwhile. The symptoms of any blossom infections that might have occurred around May 23 are not yet visible. Better to be safe than sorry!
- Apogee/Kudos (prohexadione calcium) supress shoot blight. When Apogee/Kudos are applied after 10 cm of new shoot growth, the vegetative growth reduction is less but the product will still slow fire blight progression.
- 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 (0.05%). 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 – 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).
Insects
Apple Insects
Please refer to the petal fall insecticide decision table for a quick overview of your choices for apple trees. 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.More Notes:
- Monitor for white apple leafhopper. Sevin XLR applications for thinning in mature blocks will control leafhopper but monitor non-bearing plants for leafhopper. If treatment is required, a neonicotinoid, Sivanto Prime, or Exirel would control leafhopper.
- Monitor for rosy apple aphid and green aphid in young trees and nursery plantings where feeding can disrupt shoot growth. If leaves are curling high, high water volumes are needed for effectiveness.
Apple and Pear: Codling Moth
Degree Day and Treatment Timing Predictions
The biofix dates for this season are June 1 for early and June 5-6 for late regions determined by Erika Bent, APM. Jeff Franklin, AAFC, ran the degree day model to predict when degree day thresholds will be met for treatments.
Codling Moth Treatment with Rimon
Timing: The treatment timing for Rimon is 80 degree days Celsius from biofix.
Prediction: According to the current forecast, the 80 degree day threshold is expected to occur by June 14 for early regions and June 16 for late regions.
Codling Moth Treatment with Egg Hatch Products
Products: Assail, Calypso, Delegate, Intrepid, Altacor, and Exirel
Timing: The treatment timing for egg hatch products is 100 degree days Celsius from biofix.
Prediction: According to the current forecast, the 100 degree day threshold is expected to occur by June 16 for early regions and June 18 for late regions.
Products: Assail, Calypso, Delegate, Intrepid, Altacor, and Exirel
Timing: The treatment timing for egg hatch products is 100 degree days Celsius from biofix.
Prediction: According to the current forecast, the 100 degree day threshold is expected to occur by June 16 for early regions and June 18 for late regions.
Product: Imidan
Caution: All hand thinning activities must be completed prior to application. No hand thinning can occur on trees treated with Imidan.
Timing: Control of codling moth with Imidan is typically slightly later at 140 degree days after biofix.
Prediction: According to the current forecast, the 140 degree day threshold is expected to occur by June 20 for early regions and June 22 for late regions.
The models were run on Monday, June 11 with a degree day threshold of 10 degrees (C) using Kentville weather station data. Stay tuned for updates as the model will be recalculated with changes in the forecast.
Timing: Control of codling moth with Imidan is typically slightly later at 140 degree days after biofix.
Prediction: According to the current forecast, the 140 degree day threshold is expected to occur by June 20 for early regions and June 22 for late regions.
The models were run on Monday, June 11 with a degree day threshold of 10 degrees (C) using Kentville weather station data. Stay tuned for updates as the model will be recalculated with changes in the forecast.
Reminders:
- Discard your old codling moth traps in case the old septum still attracts insects.
- Those growers that do their own monitoring for codling moth should hang traps in orchard blocks.
Fruitlet Thinning
Apple Fruitlet Thinning
This year a new thinner called Accede is registered and has activity at up to 25 mm fruitlet diameter but supposedly works best at 18 mm. Product supply is limited but you may wish to try it on a small scale.
Recommendations:
- Most varieties are still within the thinning window but not necessarily early varieties. The thinning window will close soon so act soon if you plan to chemically thin.
- The optimal temperature for thinner activity is between 21-24°C. In cooler temperatures the thinning activity is less and in warmer temperatures the thinning activity is more. The danger zone is when temperatures will exceed 29°C within 4 days of applying a thinner. Keep an eye on hot temperatures late in the week as you may want to reduce rates of thinners to avoid overthinning. However, as fruitlets get bigger than 12 mm the risk of overthinning is less.
- If you are concerned about overthinning, remember slightly higher temperatures observed in 2020 and 2021 and reflect on your thinning program.
- 2020: Average daytime temp was 27.9°C with two of those days (June 18 and 19) above the danger zone of 29°C. The temp got higher than forecast and it fooled us.
- 2021: There were also two days above the danger zone (June 7 and 8).
- This week presents good warm conditions for using MaxCel/Cilis Plus for good thinning activity on Gala and for defruiting trees. For small-fruited varieties, there is a high chance of gains in fruit size (20 g/fruit) when MaxCel/Cilis Plus is used for chemical thinning around now at 10-15 mm fruitlet diameter. Just remember that the label says to avoid spraying it when ambient temperatures exceed 30°C.
- If rescue thinning is necessary, Accede treatments may be applied to high value varieties next week when they are expected to measure 18-25 mm. Earlier treatments are expected to be most effective.
- Remember that you can adjust your spray pattern based on fruit set on the top versus bottom of the tree. Usually late in the thinning window the target is excess fruit set in the top of the tree so you may direct your spray. The recommendation is for the 12 mm sprays to direct 80% in the top and 20% in the bottom. For the 18 mm spray direct 100% in the top of the tree.
Product Overviews:
Defruiting Young Trees
- 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 (avoid Gala, Ambrosia, Golden Delicious, Red Delicious).
- 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. A second application will likely still miss some fruit so consider that hand thinning may still be required anyway.
- Choosing to use Fruitone (NAA) in this mixture instead of MaxCel will result in chemical pinch at the terminal bud that stunts growth.
- Using currently available products, the amount of product that would be needed to completely defruit trees in our climate would likely negatively affect tree growth. Therefore, expect that hand thinning will still be required.
Pear Fruitlet Thinning
- The Maxcel thinning window is 8-14 mm and early treatments are most effective. The window has either closed or will very soon.
Peach Hand Thinning
- Hand thin early-maturing varieties first for increasing the chances of fruit sizing.
- Start thinning after natural drop is clear.
- Space fruit clusters about 15 cm apart.
Horticulture
Cover Crops
- Perennia has a series of videos about cover crops by Sonny Murray and Rosalie Gillis-Madden that can be accessed from our website.
- Summer grasses such as pearl millet and sorghum-sudangrass that have been growing in popularity lately can be planted from mid-June until early August.
Mowing
- Keeping the orchard floor cover mowed to 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 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.
- 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. If newly planted trees have received a settling rain then 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
- 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).
Nursery Trees
- Consider staking to prevent blowouts. Even if not tied, the rod acts as a physical barrier to mechanical injury.
- Treat for tarnished plant bug and green aphids.
- Remove rootstock leaves when they are tender and before shoots become woody.
- For bench grafts, leave some shoots on the rootstock to feed the scion as the callus tissue develops. Locally, rootstock leaves have been stripped when the scion has 8-10 leaves. Early in the season, leave at least an extra scion leader for insurance.
- Remember the importance of weed control in nurseries. Management practices now will impact the outcome of the final tree.
Events and Notices
Save the Date - NSFGA Summer Tour August 7
The 2024 NSFGA Summer Orchard tour will be held on Wednesday, August 7th, 2024. This year NSFGA is bringing back the evening portion of the tour and hosting a barbecue chicken dinner, with families welcome to join for an evening meal!A bus will be provided, seats are limited. Registration is not required and the event is free of charge.
Events like this are only possible through sponsorship! NSFGA has announced that sponsorship opportunities are now available.
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
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.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
