Table of Contents:
- 2026 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
- Spring Growth
- Suckers
- Grafting
- Mowing
- Root Pruning
- Pruning and Training
- Weed Management
- Nursery Trees
- Cover Crops
Weather
2026 Degree Day Accumulations
The rollercoaster of seasonal temperatures continues with the plunge to below-average temperatures over the past week. The cumulative degree days are now between the 5- and 10-year averages and behind last year (Figure 1).
This past weekend was notably colder than usual, with an average temperature of 7.4 °C, ranking as the fifth coldest for the final three days of May on record. Only the years 1917, 1923, 1943, and 1953 experienced lower temperatures during this period. Development stages are now lagging behind what they were at this same time last year.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to June 1 for the past 17 seasons. Provided by Harrison Wright (AAFC Plant Physiology).
- Approximately 5% less plant development heat units compared to the 5-year average, and 3% more compared to the 10-year average.
- Approximately 9% less plant development heat units compared to 2025, and 7% less compared with 2024.
- Approximately 10% less insect development heat units compared to the 5-year average, and equal 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 Monday the average diameter of ten king fruitlets on Idared was 5 mm (Figure 2). Honeycrisp was at about 60% petal fall especially when the petals were ruffled and the king fruitlet measured about 4 mm. Ambrosia was at about king bloom petal fall with a range of stages from pink to petal fall throughout the tree canopy. Since last week, buds have moved forward about 0.5 growth stages and development is slightly behind last year.
Figure 2: Bud development in an early region on Middle Dyke Road in Kentville on June 1. Shown from left to right: Idared, Honeycrisp, Ambrosia.
The timing for the first application of Apogee/Kudos is when new shoot growth reaches 2.5–7.5 cm. In this early region, shoot growth is expected to surpass the early application window shortly. Over the past week, terminal shoots across all monitored varieties have doubled in length. Current measurements indicate that Idared averages 12 cm, Honeycrisp 7 cm, and Ambrosia 6 cm (Figure 3). While Idared shoot growth is consistent with last year’s measurement, Honeycrisp and Ambrosia are developing slightly behind. Idared now has 6 fully expanded leaves, with 3 additional leaves not yet expanded, while Honeycrisp and Ambrosia each have 5 fully expanded leaves and 2 leaves unfolding.
Figure 3: Terminal shoot growth in an early region in Greenwich on June 1. Shown from left to right: Idared, Honeycrisp, Ambrosia.
Pear and Stone Fruit Buds
Figure 4: Bud development on June 1. Shown from left to right: An early region in Greenwich with pear, peach/nectarine, and European plum.
I observed twinned fruitlets on peach from single flower buds that developed into two fused fruits (Figure 5). Twinned fruit is most commonly caused by stress during bud initiation the previous season, notably during a drought. Resources from California describe that twinned fruit are closely connected with water stress. Cold temperatures during spring can also cause unexpected bud development and some twinned apple fruit was noted in 2018 after the spring freeze. Some peach varieties are likely more susceptible than others.
Figure 5: Twinned fruitlets on peaches from a single bud that might be a result of the 2025 drought or cold spring temperatures.
Diseases
Apple – Scab
Table 1: Apple scab infection events in Kentville from May 27 to June 2, based on the Modified Mills Table.
-Assuming a green tip date of April 19. 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:
- Reapply a protectant fungicide on a 5-7 day interval, using the shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
- Primary spores are still present and primary infection events are still a risk. By this coming Sunday, ascospore maturity is forecast to reach 99.8%.
- Ascospores are maturing at a rate of 0.1-0.6% per day, where higher rates occur on warm days.
- 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.
- Remember, if using SHARDA CAPTAN 48 the rate equivalent to other captan products is 5 L/ha (2.4 kg of active ingredient).
Apple – Powdery Mildew
Powdery mildew infections can be expected when conditions are warm (10-25°C), humid and dry.
Recommendations:
- Infections are possible during this coming warm and dry weather around June 4 to 5.
- 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.
- Do not use any products with powdery mildew activity more than two times consecutively to avoid resistance development.
- Fungicide options for petal fall with reminders:
- Group 3 products Nova and Fullback are very effective. However, do not use them more than two times consecutively to avoid resistance development. They are ineffective on scab due to resistance, so use in conjunction with a fungicide that manages apple scab.
- Group 7 containing products are Luna Tranquility, Inspire Super, Sercadis, Excalia, Fontelis. For Luna Tranquility, activity for scab control is only provided at the high label rate. Fontelis contains a mineral oil in the formulation so do not use near captan or folpet products.
- Group 3 + 7 Aprovia Top is a combination product, therefore, be careful that you do not make more than two consecutive applications of group 3 or group 7 containing products.
- Group 52 Migiwa is a new chemical that may be incorporated into the program to strengthen resistance management. Migiwa also has control of apple scab and it should always be used at the high label rate.
- Group U13 Gatten is a new group. The product does not have activity on apple scab.
- Group 50 Property is a new group. The product does not have activity on apple scab.
- There is industry resistance to group 11 products such as Flint so it should NOT be used for powdery mildew management.
- Other products are listed in the pest management guide.
Fire Blight Prevention and Shoot Blight Management
Recommendations:
- If a blossom blight infection occurred on May 20, the symptoms are not yet visible. The Maryblyt model gives rough guidance and says the infections are only 20% progressed. Usually we see the symptoms of infection after about 3 weeks, at around mid-June. Stay tuned.
- 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 when tissues are wet. Pinching causes open wounds like a trauma event and bacteria are transported from cankers to wounds in wet weather.
- Apogee/Kudos (prohexadione calcium) suppress shoot blight. Apogee/Kudos is first applied at 2.5-7.5 cm of shoot growth.
- Please note that the product Apogee is discontinued by BASF. Kudos is another product with the same active ingredient and will remain available.
- 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. Early application might even thicken cell walls of the flower pedicels giving some added protection from blossom 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.
- The product is not systemic so good coverage with high water volume is required.
- 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)!
- Use low rates on young apple trees to avoid delaying growth too much.
Apple and Pear – Fire Blight Blossom Blight
Bacteria multiply rapidly in warm temperatures, especially when occurring over consecutive days. The Maryblyt model criteria is used to predict blossom blight infections. Periods with high fire blight bacterial populations are defined by Maryblyt as having an Epiphytic Infection Potential (EIP) greater than 100 - representing 100% of the bacteria load needed to cause infection.
Blossom Blight Risk
- Bacterial growth on open flowers is currently very low but it is forecast to increase rapidly during the forecast heat.
- On Thursday, June 4 the EIP is forecast to reach 85. On Friday, June 5 the EIP is forecast to exceed the 100 threshold indicating high bacterial populations.
- Wetting after the forecast heat could trigger an infection. Stay tuned. Alert emails will resume.
Recommendations:
- Check if newly planted trees are in bloom for the upcoming risk.
- 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.
- 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.
- There is plenty of bloom on one-year-old wood that is delayed relative to the rest of the tree.
- 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!
- If you would like to join the alert contact list, please let me know or sign up online.
- Ideally, you will monitor your own farm-specific situation with PomeBlight using a selected weather station. The user account and PomeBlight tool are free. Follow my 17-minute Quickstart video or Quickstart PDF document.
- Contact me if you have ANY questions!
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
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 - 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), white apple leafhopper, green and rosy apple aphids, and curculio.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:
- Cool nighttime temperatures over the past week have momentarily stopped moth activity like obliquebanded leafroller, eyespotted bud moth, and codling moth.
- If you have not already treated for rosy apple aphid, be aware that they thrive in cool and wet weather because their predators are suppressed. For those of you that have treated, it's great to be on top of the issue!
- 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. Cold weather slows their activity.
- 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 are not active in these cool temperatures but warm evenings will eventually encourage their flight. Organic apple growers should have traps in place and consider the timing of mating disruption for codling moth. When using Isomate-CM/OFM for codling moth mating disruption, have the ‘twist ties’ placed in the orchard blocks by petal fall (prior to the start of male moth flight).
Stone Fruit - Postbloom Insects
Recommendations:
- Be aware of bee toxicity warnings on pesticide labels and take precautions while nearby crops are in bloom.
- 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 is usually needed about 10 days after the first.
- 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. Apply one to two applications of one of the pyrethroids Up-cyde, Ambush, or Pounce listed in the Stone Fruit Pest Guide for peaches. Repeat treatment in 5-7 days if additional stings are detected. (Matador was cancelled from registration in peaches.)
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 into leaves.
- 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 registered for control of pear psylla with the same recommended application time.
Thinning
Pollination Comments
Pollination weather this year not ideal and it could complicate assessments of fruit set. It is difficult to generalize observations because of the various stages of bloom throughout the Valley this year. Here are a few thoughts:
- There are plenty of flowers on trees; far too much for a high quality crop. Heavy flowering could be a stress response related to the drought the previous year. Less shoot growth redistributed resources to reproduction. Trees that had good reserve status were equipped for good bloom.
- Cold weather can reduce the available pollen, reduce bee activity, and slow fertilization. However, cold weather also extends the lifetime of a flower and the protracted bloom widens the pollination period. Cold weather can result in high fruit set if many flowers are receptive when good pollination conditions eventually occur. Remember the protracted bloom on Gala last year and how hard it was to thin.
- Windy conditions can reduce bee activity and dehydrate the stigma.
- It takes only a few days of good pollination weather to set a crop. Last year was a good example. Trees need to set only 5-10% of flowers for a commercial crop.
Apple Fruitlet Thinning
The timing of chemical thinning is based on the average size of the king fruitlet. The size of the side fruitlets is irrelevant for treatment timing. 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. The weekly forecast currently looks quite good for thinner activity. However, temperatures may behave unexpectedly on Thursday, June 4 and the forecast is already on the borderline of extreme heat.
Recommendations:
- At the tailgate meeting on Monday, the group discussed if it's practical to use nibble thinning where fruit set is suspected to be high or return bloom is a concern. There was some interest in a petal fall application especially for varieties where growers wanted to do blossom thinning but it didn't work out.
- This year it might be difficult to use Sevin at petal fall because of protracted bloom and the risk of injury to bees visiting late flowers.
- A low rate of Fruitone/Maintain can be used for a petal fall application at rates of around 150-300 mL product in 1000 L water. Fruitone/Maintain is not as aggressive at petal fall as it is at 7-12 mm.
- The disadvantage is that you will not have enough time to assess the outcome of the petal fall thinner before you need to reapply another thinner.
- Only use a petal fall thinner on varieties where you are comfortable there is normally too much fruit set (i.e. Gala).
- Historically, it is best to wait for warm temperatures for using MaxCel or Cilis Plus (at least above 18°C).
- Local research with Brevis suggests:
- The early timing is most effective (8-10 mm).
- On Honeycrisp, at 8-10 mm, the maximum rate of 2.2 L/ha can cause overthinning. Use low to moderate rates on Honeycrisp depending on the weather. When fruit size is >13 mm, increase rates.
- On Gala, the lowest rate is not effective even in high temperatures. Use moderate to high rates during 8-10 mm. Brevis is not a silver bullet so keep in mind for hard-to-thin varieties like Gala that a nibble thinning approach might be required (especially because of protracted bloom).
- 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 it is also an insecticide and care should be taken to avoid contact with bees.
- Research has demonstrated that there is a recommended crop load associated with trunk diameters of apple trees in high density systems that are under eight years old. 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 is more appropriate.
- During the thinning window I will comment on the suspected carbohydrate status of the trees. It is still too early to comment.
- 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).
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.
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 likely result in chemical pinch at the terminal bud that stunts growth.
Pear Fruitlet Thinning
- The Maxcel and Cilis Plus thinning window is 8-14 mm and early treatments are most effective.
- Brevis is a new thinner that is registered for use from late petal fall until 16-18 mm. The registrant recommends using Brevis on pears at the low rate and at the later timing of 12-14 mm.
- Avoid applying to trees less than 4 years old.
- Do not add any adjuvants that increase droplet spreading or penetration.
- Do not spray on wet leaves.
- Apply when air temperatures are between 10°C and 29°C and delay application if temperature will exceed 29°C within five days of application.
- Avoid drift to plum and cherry trees.
Horticulture
Spring Growth
During a recent farm visit, a concern was raised about the presence of small leaves. Issues like this are challenging to explain because multiple factors are at play. In this case, the symptoms were observed on Honeycrisp trees across a range of rootstocks, tree ages, blocks, and nursery sources. The trees otherwise appeared healthy, with no visible root system issues or signs of chemical injury, and flowering was normal.While I always aim to provide clear explanations, part of the purpose of this newsletter is to share timely observations from the field. I'm sharing this observation now in case you are seeing similar symptoms in your own orchard.
The Orchard Outlook Committee discussed several possible contributing factors; however, these should be viewed as ideas rather than definitive answers. One possibility is a response to environmental stress, including drought conditions. The leading theory is related to weather patterns with periods of above-average temperatures followed by cooler-than-normal conditions and frost events. Cooler spring temperatures can suppress hormones involved in cell division and leaf development, such as gibberellins and cytokinins. Reduced levels of these hormones may limit cell division and expansion, resulting in smaller or curled leaves. Additionally, these conditions may affect nutrient uptake, potentially reducing the availability of key elements like zinc.
Figure 5: An example of little and distorted Honeycrisp leaves. Photos taken on May 27, 2026.
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 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
- Our region benefits from leaving a nurse limb but there is no consensus on how long to leave the limb. More vigorous rootstocks likely need the nurse limb for longer.
Mowing
- Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of post-bloom insecticide applications.
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.
- Consider the effect of the drought last year and whether the treatment would be too aggressive on trees.
Pruning and Training
- Select strong terminals on young trees and remove competing terminals to single the tops if there are no re-entry intervals active and before the shoots get woody.
- 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).
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.
- The following residual herbicides can persist longer than usual in extreme circumstances like drought: Authority, Chateau, and Alion.
Nursery Trees
- Treat for tarnished plant bug and green aphids.
- Remove rootstock leaves when they are tender and before shoots become woody.
- On last year's bench grafts, single to the main stems.
- 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 that can be accessed from our website.
- Summer grasses such as pearl millet and sorghum-sudangrass that have been a popular choice can be planted from mid-June until early August.
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: Harrison Wright, Danny Davison, Larry Lutz, Joan Hebb, Ian Willick, Suzanne Blatt, Keith Fuller, Heather Rand, and Colin Hirtle.
Written by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
