Today's newsletter reports average king fruitlet diameters on varieties ranging from 9.8 mm to 14.9 mm so the window of opportunity for chemical thinning will soon come to a close. More thoughts on fruit set and chemical thinning are discussed. Symptoms of recent powdery mildew infections are visible on young leaves. Please be aware of the upcoming risk of fire blight blossom infections on open blossoms in young trees. Some of you may be due for post bloom weed control. Thanks to the ongoing commitment of the Orchard Outlook Committee members.
Table of Contents:
- 2025 Degree Day Accumulations
- Apple Buds
- Apple - Scab
- Apple - Powdery Mildew
- Fire Blight Prevention and Shoot Blight Management
- Apple - Fire Blight Blossom Blight
- Apple - Black Rot
- Apple Insects
- Pear Insects
- Fruit Set
- Apple Fruitlet Thinning
- Defruiting Young Trees
- Suckers
- Mowing
- Pruning and Training
- Weed Management
- Nursery Trees
- Cover Crops
- Marbicon Pesticide Courses
Weather
2025 Degree Day Accumulations
The cumulative degree days are ahead of the 5- and 10-year averages (Figure 1). Jeff Franklin notes that, "The warm temperatures experienced over that last couple of weeks has kept us above average in terms of degree days . Looking specifically at the base 5 °C degree days, this is the third warmest year going back to 2011. The 30-day forecast from Environment Canada suggests that this trend is likely to continue."
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 Plant Physiology).
- Approximately 10% more plant development heat units compared to the 5-year average, and 17% more compared to the 10-year average.
- Approximately 4% more plant development heat units compared to 2024, and 28% more compared with 2023.
- Approximately 7% more insect development heat units compared to the 5-year average, and 16% 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 9, ten king fruitlets of each of the following varieties were measured to get a rough average (size of king fruitlets guides application timing). The Idared measured 14.9 mm, Honeycrisp 13.2 mm, and Ambrosia 9.8 mm (Figure 2). Similar measurements were taken in Grafton and South Berwick, including Gala at 10.0 mm.Over the past week, Idared grew 1 mm/day, Honeycrisp grew 0.9 mm/day, Ambrosia grew 0.6 mm/day, and Gala grew 0.6 mm/day. The relatively slower growth rate of Ambrosia and Gala might be explained by their initially small fruit size when measured last week. Both varieties were still at the petal fall stage and measured less than 7 mm, so there was likely a lag period from petal fall to 7 mm before fruitlet growth rates increased. Typically fruitlets grow about 1 mm each day in average temperatures.
Early varieties have likely surpassed the thinning window of opportunity. Later varieties and later regions 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 size in an early region on Middle Dyke Road in Kentville on June 9. Shown from left to right: Idared (14.9 mm), Honeycrisp (13.2 mm), Ambrosia (9.8 mm). The king fruitlet is measured to represent fruit stage for thinning.
Diseases
Apple – Scab
Table 1: Apple scab infection events in Kentville from June 3 to June 10, 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 April 20. 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 April 20. 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 7 and then the ongoing wetting event would have released the final primary spores. Models are not completely accurate so wait 2 weeks after ascospores are depleted and continue to stay protected on 5-7 day intervals. This also allows time for symptom development and assessment of recent primary apple scab infections. But there is now a light at the end of the tunnel!
- Fungicide options can be limited this time of year... so let's review some options:
- 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 that is ideal. 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/Vantana/Downforce 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.
- Migiwa is registered for scab control and it has a short REI of 12 hours. Just be sure to use the high rate of 220 mL/ha so that the powdery mildew that is present isn't exposed to a sublethal dose at the low rate. We want to preserve this product efficacy for powdery mildew.
- 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. 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.
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:
- Protection may continue on 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 for later this week would suggest that this week offers the opportunity for infections to happen during the warm and dry weather.
- New products registered this year for apple powdery mildew with unique chemical groups include:
- Migiwa group 52, control of scab, short REI of 12 hrs, max 3 apps total.
- Gatten group U13, no activity on scab, short REI of 12 hrs, max 4 apps total.
- Property group 50, no activity on scab, short REI of 12 hrs, max 4 apps total.
- Some notes about industry-standard products:
- The chemical group 3 products Nova/Fullback are very effective. Fullback and Nova are systemic and given a long drying period of 24 hrs they should be well-absorbed into the plant. (Fullback and Nova will not provide scab protection due to industry-wide fungicide resistance.)
- If you're using Luna Tranquility for powdery mildew, concurrent activity for scab control is only provided at the high rate.
- There is no expected resistance to chemical group 3 and 7 products so the products are expected to be effective.
- There is industry resistance to group 11 products such as Flint so it should not be used for powdery mildew management.
- To avoid resistance development, do not use any products with powdery mildew activity more than two times consecutively (without rotating to another chemical group with powdery mildew activity).
Figure 3: Symptoms of this year's new powdery mildew infections. Only young leaves are susceptible to infection so these symptoms on the 4th and 5th newest leaves are likely a sign of infection that occurred last week when these leaves were young. Photo taken yesterday on June 9.
Fire Blight Prevention and Shoot Blight Management
Recommendations:
- 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.
- Even if bacterial EIP populations are low, do not pinch flowers on young trees in wet weather. Pinching causes open wounds like a trauma event and bacteria are transported to wounds in wet weather.
- Apogee/Kudos (prohexadione calcium) suppress shoot blight.
- Follow up with a second application applied around 14 days later. 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 product has activity for three to four weeks following application and then it is degraded by the plant. When you re-apply Apogee/Kudos it extends the period of activity to give season-long protection of terminal shoot growth by thickening cell walls.
- 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.
- Use low rates on young apple trees to avoid delaying growth too much.
Apple – Fire Blight Blossom Blight
Current and Forecast Blossom Blight Risk
- As far as I'm aware, signs of early blossom blight infections are not yet visible and are not expected yet. Last year we started to see the symptoms of early infections around June 18.
- Industry alerts will continue while there are blossoms in young plantings.
- The risk of bacterial growth on flowers is low for today but it is forecast to increase. On Wednesday, June 11 the EIP is forecast to reach 73. On Thursday, June 12 the EIP is forecast to exceed the 100 threshold indicating high bacterial populations.
- An alert email will be sent tomorrow with updated predictions.
- It looks like streptomycin is the only option for this coming infection period. Rain on Tuesday and Wednesday would keep flowers wet into Thursday so Kasumin is not an option.
- Also, there is no opportunity to pinch blossoms before the upcoming infection potential on Thursday due to forecast rainy periods.
- Preliminary Scenarios (stay tuned for updates):
- Streptomycin applied on Wednesday could be premature. If new unprotected flowers open they will be at risk.
- Streptomycin applied on Thursday is forecast to provide protection on the day of application and for the foreseeable future.
Please note: If you're using PomeBlight there is an issue with how it is recording daily maximum temperature after 4 PM. We are aware of the issue but will need to wait until after fire blight season to address it. For ease of use, we recommend that you check the forecast before 4 PM. If you check the model after 4 PM then you will need to manually enter the maximum temperature for the day using the value from your Davis weather station.
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.
Apple – Black Rot
Recommendations:
- Based on our limited knowledge, the highest risk of infections is theoretically between petal fall and 4-6 weeks later.
- 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 and if damaged can allow entry of the black rot fungus. Be cautious with spray mixtures (calcium, foliar nutrients) that could create an entry point for the pathogen.
Insects
Apple Insects
Choose post-bloom insecticides according to the pest complex on your scouting report. Insects might include the caterpillar complex, stinging bugs (mullein bug), European apple sawfly, green and rosy apple aphids, curculio, European red mite, and white apple leafhopper.Refer to the Apple Efficacy Guide for product selection. You may begin by determining the product and rate for your most difficult to control pest and then note the other pests that will be managed by your product selection and whether or not additional products are required. Take note of the higher rate required for some pests.
Recommendations:
- Stinging bugs are checked using limb tap samples when the nymphs are very small. Applications have been delayed this year so watch for updates from Erika or continue scouting prior to application. In my own limited attempts at tapping, the stinging bugs have been difficult to find.
- Leafrollers are present and can be found in curled leaves where there are signs of chewing activity (Figure 4). There are a variety of leafrollers that may be present and a product like Intrepid can be a good option for control.
- Leafhoppers can be found feeding on the underside of leaves and they will move forward or backward. Leafhopper nymphs are found on cluster leaves close to the main trunk or large branches, not on terminal shoots. Leafhoppers are often controlled by Sevin insecticide when used as a thinner. Monitor non-bearing plantings for leafhopper if they have not been treated with Sevin. If treatment is required, a neonicotinoid, Sivanto Prime, or Exirel would control leafhopper.
- Monitor for aphids in young trees and nursery plantings where feeding can disrupt shoot growth. If leaves are curling high water volumes are needed for effectiveness. Green aphids are starting to become obvious on terminal shoots (Figure 5).
- Codling moth flight occurs when nighttime temperatures are above 10°C. Erika Bent provides a biofix date for the industry based on several regions and the date has not yet been determined. Setting biofix is usually challenging in a year with fluctuating temperatures. We will report when the biofix date is determined to provide some treatment timing recommendations.
Figure 4: Leafrollers are in curled leaves. Photo taken yesterday.
Figure 5: Green aphids were noticeable on terminal shoots yesterday. Usually ants are a good indicator to take a closer look.
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 young tissues because of rapid penetration.
- 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.
- 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.
Thinning
Fruit Set
Every year is challenging to assess fruit set but this year had an extra complication with the doubt in our minds after pollination. Remember how the story went in 2004 when they were initially doubtful and then a week later it was clear that fruit needed to be thinned? The good news is that there is generally a lot of fruit out there this year too, despite the mostly poor pollination conditions.
Last week was difficult to assess when fruitlets were small but now with sizing and early fruit drop it is more clear that a lot of situations have plenty of strong fruit. Figure 6 is a photo of the same clusters on June 2 (left) and one week later on June 9 (right). The photos show how much more clear the size differentiation became over a one week period.
There is a lot of variability out there on individual farms and blocks in terms of kings or lateral fruit set. Fruit set also varies on trees from bottoms to tops and heavy or light set within individual clusters depending on when flowers opened. For whatever reason, I've seen and heard of many situations with heavy fruit set on gala.
If chemical thinners were applied last week, the influence of their thinning activity is not yet clear because they were applied less than one week ago. If fruitione was used last week then the observed heat was expected to increase thinning activity.
Figure 5: The same clusters were observed over a one-week period. The top photos are Cluster 1 on June 2 and later on June 9; where only one fruit dropped and the remaining laterals appear strong. The bottom photos are Cluster 2 on June 2 and later on June 9; where the king fruit grew the most but two other laterals are also growing.
Table 2: The recommended crop load for young high density apple trees based on trunk diameter. Honeycrisp and Gala trees can have 6 fruit/cm² or if you would like larger Gala fruit then 4 fruit/cm². For the chosen column, note how many fruit can be cropped based on trunk diameter. For example, at 6 fruit/cm² , a Honeycrisp tree with a 2" trunk diameter would have 122 fruit.
Apple Fruitlet Thinning
The timing of chemical thinning is based on the average size of the king fruitlet. After petal fall, fruitlets typically grow about 1 mm each day in average temperatures. Chemical thinning occurs when king fruit are 5 to 18 mm in diameter and is most effective from 7-12 mm.
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.
Recommendations:
- With all of the variables discussed above for fruit set, a lot of growers have settled on not reducing rates and are generally using at least their usual rates.
- This week's thinning conditions present average temperatures but fruitlets are getting bigger and are less responsive to thinners when they are larger than 12 mm. On large fruit, higher rates are unlikely to result in overthinning.
- Less fruit set has been observed in tree bottoms. If this is the case, target the thinners to tree tops for these later chemical thinner applications.
- Accede is registered for late thinning when fruitlets are 18-25 mm. Earlier treatments are expected to be most effective.
- When using Sevin in high density orchard do not exceed 3.22 L of product/ha/year. In low density orchard do not exceed 2.15 L of product/ha/year.
Defruiting Young Trees
- Some of the fruit on young trees can be removed using 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 the economics if hand thinning may still be required anyway.
- Choosing to use Fruitone (NAA) in this mixture instead of MaxCel/Cilis Plus will result in chemical pinch at the terminal bud that stunts growth.
Horticulture
Suckers
- Suckers are becoming quite strong by now and would be resistant to sucker control using contact herbicides if suckers are taller than a few inches in height. Remove woody suckers by cutting or ripping to avoid resource competition, the risk of systemic herbicide uptake, harbouring pests like fire blight shoot blight.
- If suckers are more prevalent because of exposed roots due to frost heaving, try to hill the soil to cover the roots.
Mowing
- Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.
- Mowing and herbicide strips help to prevent issues with two-spotted spider mite (John Michael Hardman).
Pruning and Training
- 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).
Weed Management
- If you applied a residual herbicide about 6-8 weeks ago (end of April) then you are likely due for reapplication.
- For young trees (1-2 yrs), a good option could be Simazine and Dual II Magnum with Reglone for burndown.
- In established trees (>3 years), a good option is Alion and Ignite when conditions are dry and hot before an upcoming rain.
- If using glyphosate alone, consider coarse droplets and low pressure to reduce drift. By the approaching summer solstice, glyphosate applications become more risky.
- When burndown products are needed, consider that Reglone works in cool and cloudy conditions whereas Ignite requires warm and sunny conditions. Also, applying Ignite when leaves are wet is ineffective.
- 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.
Nursery Trees
- 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. Encourage the growing point to be successful!
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.
Events and Notices
Marbicon Pesticide Courses
In-person full-day pesticide applicator exam preparation courses will be offered in mid-June by Marbicon.- Jun 9 - Mon – Truro – Colchester Legion Stadium Lounge, 14 Lorne St.
- Jun 11 - Weds – New Germany – Anglican Hall, 5311 Highway 10.
- Jun 13 - Fri – Berwick – Berwick Legion Hall, 232 Main St.
Pre-exam courses are $130 including HST.
Instruction starts at 9:00. Expect to be done around 4:00-4:30.
People sitting in for 5.0 recertification points pay $120 including HST.
Points people can expect to be done around 3:15.
Doors open at 8:30 am for registration & settling in.
Pay at the door or by corporate/government purchase order.
If paying by e-Transfer, please add for whom and for which date.
Sorry, no Visa, MC, or Debit.
HST is included in the above prices.
Food & drink is on your own.
A course manual will be provided. Bring a pen.
NOTE: Pesticide exams are normally written online, NOT at this course.
Contact NS Environment for further details on writing the exam.
A course is not required before challenging the pesticide exam, but it usually helps.
Cash or cheques (payable to Marbicon Inc.) or e-transfer to marbicon@eastlink.ca
Contact Jim Jotcham at marbicon@eastlink.ca or at 902-538-7101 for more details and/or to pre-register.
Pest Management Guide
We offer printable PDFs of the guides from our website:
Online pest guides are also available without login (https://www.perennia.ca/pest-guides/) and with login on your Perennia account (https://www.farmdatatools.perennia.ca/). Using the online tool you can filter for organic and conventional options, search for key information, and sort based on information of interest.
This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Suzanne Blatt, Larry Lutz, Danny Davison, Heather Rand, Ariana Willick, Joan Hebb, Ian Willick, and Shawkat Ali.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
