Today's newsletter reports average king fruitlet diameters on apple varieties ranging from 5.5 mm to 7.3 and pears at 9.8 mm... so welcome to the window of opportunity for chemical fruitlet thinning! There is an opportunity for thinning this week and weather implications are discussed. In terms of diseases, primary apple scab infections are still possible but the end is in sight. Please be aware of the presence of rattail flowers and flowers on young trees and develop a strategy because the risk of fire blight blossom infection approaches late this week. Thanks to the ongoing commitment of the Orchard Outlook Committee members.
Table of Contents:
- 2025 Degree Day Accumulations
- Apple Buds
- Pear and Stone Fruit Buds
- Apple - Scab
- Apple - Powdery Mildew
- Fire Blight Prevention and Shoot Blight Management
- Apple and Pear - Fire Blight Blossom Blight
- Apple - Black Rot
- Apple - Postbloom Insects
- Stone Fruit Insects
- Pear - Postbloom Insects
- Fruit Set
- Apple Fruitlet Thinning
- Defruiting Young Trees
- Pear Fruitlet Thinning
- Suckers
- Grafting
- Mowing
- Root Pruning
- Pruning and Training
- Weed Management
- Nursery Trees
- Cover Crops
- Marbicon Pesticide Courses
Weather
2025 Degree Day Accumulations
At our committee meeting, Jeff also discussed the most recent seasonal forecast from Environment and Climate Change Canada. He says it suggests that there is a 95% probability of above-average temperatures from June to August. The weather network seasonal forecast suggests this also.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to June 2 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 16% more compared to the 10-year average.
- Approximately 4% more plant development heat units compared to 2024, and 20% more compared with 2023.
- Approximately 3% more insect development heat units compared to the 5-year average, and 9% 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. Following the developmental standstill at bloom, this past week saw above-average temperatures and a relatively fast change in growth stage.Yesterday on June 2, 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 7.3 mm, Honeycrisp 6.7 mm, and Ambrosia 5.5 mm (Figure 2). Similar measurements were taken in South Berwick and Lakeville, including Gala at 5.5 mm.
Typically fruitlets grow about 1 mm each day in average temperatures. Chemical thinning should be considered soon so 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 2. Shown from left to right: Idared (7.3 mm), Honeycrisp (6.7 mm), Ambrosia (5.5 mm). The king fruitlet is measured to represent fruit stage for thinning.
Terminal shoot growth has also progressed. Idared measured about 13.0 cm, and there was a growth spurt in Honeycrisp and Ambrosia that now measure 10-11 cm (Figure 3).
Figure 3: Terminal shoot growth in an early region on Middle Dyke Road in Kentville on June 2. Shown from left to right: Idared (13 cm), Honeycrisp (11 cm), Ambrosia (10 cm).
Pear and Stone Fruit Buds
Yesterday on June 2 at an early region in Greenwich, the pear buds measured 9.8 mm. Stone fruit are at the shuck fall stage with peach measuring 1.0 cm, and European plum measuring 1.0 cm (Figure 4).
Diseases
Apple – Scab
Table 1: Apple scab infection events in Kentville from May 27 to June 3, 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 forecast, total seasonal ascospores are expected to mature to 100% on Saturday, June 7 and then a wetting event would need to release the final spores. Therefore, primary infections are still a risk according to the model and leaf tissue should stay protected on 5-7 day intervals. Models are not completely accurate so wait 2 weeks after ascospores are depleted before reducing fungicide spray intervals.
- Do not apply captan within 7-14 days of an oil such as Agral 90 (worse if applied after oil that preconditions leaves).
- Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
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:
- Apply a protectant during petal fall to bearing blocks with a history of powdery mildew pressure. The forecast 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.
- Do not use any products with powdery mildew activity more than two times consecutively to avoid resistance development.
- 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 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 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.
- The product takes 10 days to become active so for the maximum effect on fire blight suppression it should be applied before fire blight symptoms appear.
- 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 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.
- The risk of bacterial growth on flowers is low for now but it is forecast to increase. On Wednesday, June 4 the EIP is forecast to reach 85. On Thursday, June 5 the EIP is forecast to exceed the 100 threshold indicating high bacterial populations. An alert email will be sent tomorrow with updated predictions.
- Preliminary Scenarios (stay tuned for updates):
- An antibiotic applied on Wednesday is forecast to provide protection on the day of application and the following day.
- An antibiotic applied on Thursday is forecast to provide protection on the day of application and the following two days.
- An antibiotic applied on Friday is forecast to provide protection on the day of application and the following three days.
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:
- Note that varieties known for protracted bloom like Gala still have unopened flower buds. Their long bloom period is one of the reasons why they are high risk for fire blight. 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? This could be rephrased to read, how many infections could you tolerate per tree? The answer is none.
- Have a strategy for rattail bloom. You may pinch the flowers on dry days or rely on an antibiotic.
- Don't forget about single tree replacements that might be in bloom!
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. Be cautious with spray mixtures (calcium, foliar nutrients) that could create an entry point for the pathogen.
Insects
Apple - Postbloom 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 and white apple leafhopper hatch around the bloom period and trees should be checked around petal fall for their presence.
- Stinging bugs are checked using limb tap samples when the nymphs are very small. I chatted with Erika from Agricultural Pest Monitoring in the field yesterday and according to her observations the stinging bugs are moving slowly so far. Watch for updates from Erika or continue scouting prior to application.
- 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.
- Codling moth flight occurs when nighttime temperatures are above 10°C. Dr. Suzanne Blatt's lab has captured some early moths. Erika Bent provides a biofix date for the industry based on several regions. It is usually more challenging in a year with fluctuating temperatures to set a biofix date. We will report when the biofix date is determined to provide some treatment timing recommendations.
Stone Fruit Insects
Recommendations:
- Note that pyrethroids are best used at moderate temperatures (20°C or less) and lose efficacy at around 25°C.
- Plum Curculio
- A second application for plum curculio is needed about 10 days after the first.
- 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.
- 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. Note that Matador is not registered. Repeat treatment in 5-7 days if additional stings are detected.
Pear - Postbloom 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.
- 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
Fruit Set
Pollination weather this year was not ideal and it could complicate assessments of fruit set. I'll attempt to provide some general observations here.
- Bee hives made a real difference this year because honeybees were flying on cool and cloudy days. Set seems good where hives were present.
- Orchards without hives had noticeably less bee activity and could see variability from less flower fertilization. Even without hives there were some days of acceptable pollination activity. If pollination was a concern then keep the following in mind:
- Varieties that had early king bloom had a few early pollination opportunities before the cool and wet weather. From my limited observations so far on early apple varieties like Idared, it appears that there is a good set of king fruit but that lateral fruitlets are weak. Keep this in mind when you are checking your particular situation.
- The king bloom of later varieties coincided with the poor weather but the later lateral flowers had good opportunities for pollination. From my limited observations so far on varieties like Ambrosia and Honeycrisp, it appears that there is a good set of lateral fruit but that king fruitlets are weak. Keep this in mind when you are checking your particular situation.
- If king flowers were not fertilized, they are easily dislodged by the touch of a hand. Their stems are short and yellowish. As of Monday it was unclear if unfertilized laterals could be dislodged or if they were too young.
- Regardless, in most situations there should still be plenty of fruit considering that trees need to set only 5% of flowers for a commercial crop.
- Research has demonstrated that there is a recommended crop load associated with trunk diameters of young apple trees in high density systems. Our ideal crop load for Honeycrisp based on local research is 6 fruit/cm². Our ideal crop load for Gala is 6 fruit/cm² or if you would like larger fruit then 4 fruit/cm². Refer to Table 2 to see how the recommended crop load relates to tree trunk diameter measured about 10 cm above the graft union. For large, old trees, measuring the size of typical limbs might be more appropriate.
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.
Recommendations:
- If you are unsure about fruit set, an application of Sevin XLR is recommended this week because it is mild and does not overthin. This blanket approach will ensure that you have applied a thinner and then when you have more time to assess you can follow up with Fruitone or MaxCel/Cilis Plus.
- 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.
- 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. Sevin is a thinner but note that it is also an insecticide and care should be taken to avoid contact with bees.
- 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.
- The forecast this week has some hot temperatures so be cautious about using Fruitione on Thursday or Friday especially if fruit set is already questionable.
- In the year 2020, overthinning was observed with Fruitone from applications on June 18 at 31°C and June 19 at 33°C. In 2021, overthinning was noted with Fruitone on June 7 at 33°C and June 8 at 32°C.
- As promised, here are some comments about the current carbohydrate status of the trees.
- Cool conditions combined with the recently sunny weather are expected to produce a slight carbohydrate surplus.
- Today and tomorrow the thinning conditions are optimal (no over or under thinning expected). Longer-term predictions are too unreliable.
- 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
- 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.
Pear Fruitlet Thinning (Advance Notice)
- The Maxcel thinning window is 8-14 mm and early treatments are most effective.
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.
Grafting
- The local business Maple Grove Nursery made a video last year about top working young trees. The video is available on their website called, “Reworking Young Orchard Trees (slow motion)” https://www.maplegrovenursery.ca/grafting-supplies
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).
Root Pruning
- If you are considering root pruning to reduce excessive vigour, the window of timing is from bloom and up to two weeks later. An article from Michigan State was recommended by a local grower.
Pruning and Training
- Pruning has been delayed this year and it might not be possible to prune all blocks. After bloom, making large pruning cuts can weaken trees so you may wait for summer pruning to open up tree canopies. If the orchard is near the end of its life then there is not as much concern about weakening 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.
- 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
- 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: Jeff Franklin, Larry Lutz, Danny Davison, Suzanne Blatt, Keith Fuller, Joan Hebb, Colin Hirtle, Ian Willick, Kari Brown, Ariana Willick, Heather Rand, and Shawkat Ali.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
