This week the newsletter notes pink buds and the start of measurable shoot growth. In terms of diseases, we discuss increasingly more spore load for the next apple scab infection period. You should be on alert for early blossoms opening to determine your fire blight infection risk. We also review the blossom thinning strategy. We review photos of egg hatch in European red mite and check in on spring caterpillars and note the presence of rosy apple aphids. Thanks to the ongoing commitment of the Orchard Outlook Committee members.

Weather

2025 Degree Day Accumulations

The above-average temperature trend has continued and now the current year is the second warmest spring in recent history (Figure 1). Soil temperatures are above 10°C at 35 cm depth according to the Kentville station which is also above-average. New root growth is visible on young established trees.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 12 for the past 17 seasons. Provided by Jeff Franklin (AAFC Plant Physiology).

Approximately 35% more plant development heat units compared to the 5-year average, and 34% more compared to the 10-year average.
Approximately 36% more plant development heat units compared to 2024, and 37% more compared with 2023.
Approximately 62% more insect development heat units compared to the 5-year average, and 44% 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 May 12, the Idared buds were at the full pink stage, Honeycrisp was at late tight cluster to first pink and Ambrosia was at late tight cluster (Figure 2). Bloom is expected to begin within the next week. Terminal shoot growth has also progressed with Idared measuring about 1.5 cm, and Honeycrisp and Ambrosia at around 0.5-1 cm to the growing point (Figure 3).

Figure 2: Bud development in an early region on Middle Dyke Road in Kentville on May 12. Shown from left to right: Idared (full pink), Honeycrisp (late tight cluster to first pink), Ambrosia (late tight cluster).

If you want to target the early timing for Apogee/Kudos of 2.5 cm, in some years it occurs by the pink stage. Early varieties have nearly reached the stage required for early application.

Figure 3: Terminal shoot growth in an early region on Middle Dyke Road in Kentville on May 12. Shown from left to right: Idared (1.5 cm), Honeycrisp (0.5-1 cm), Ambrosia (0.5-1 cm).

Pear and Stone Fruit Buds

Yesterday on May 12 at an early region in Greenwich, the pear buds were at late tight cluster to early first white, peach was at full bloom, European plum was at full bloom, and sweet cherry at KRDC was at full bloom (Figure 4).

Figure 4: Bud development in an early region in Greenwich on May 12. Shown from left to right: pear (late tight cluster to first white), peach/nectarine (full bloom), European plum (full bloom), and sweet cherry (full bloom) - photo from Suzie at AAFC.

Diseases

Apple – Scab

Table 1: Apple scab infection events in Kentville from May 7 to May 13, 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.

Recommendations:

The trend this season has so far been regular infection events tending toward heavy infection potential of available spores.
Over the weekend there was sufficient product wash off and plenty of new tissue growth to warrant recovering for the next wetting period. 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.
According to the forecast, ascospores are maturing at a rate of 4-7% per day. Spores are maturing more quickly now and the next spore release may be quite large at around 30%. Typically we have large spore releases around the pink stage.
Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
If you used oil for European Red Mite control, Captan should be avoided for 7-14 days after an oil application.
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.

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 should be applied pre bloom if it has not already been applied. In general, a program with two pre-bloom and one post-bloom fungicide for control of powdery mildew is needed in high-pressure situations. However, infection potential will depend on the weather conditions in a given year.
It was recently pointed out that Gatten is newly registered on apple trees for powdery mildew and is listed on the current label. In our local experience last season, Gatten gave similar control to Luna Tranquility and until we have further experience it could be considered another tool for resistance management. Verify that the new label including apple is posted on available product.

Gatten is new group U13 for powdery mildew.
Gatten does not have activity on scab.
Gatten has a short REI of 12 hours and may be applied up to 4 times each year.

Migiwa is a new chemical group 52 that may be incorporated into the program to strengthen resistance management. Migiwa also has control of apple scab and it should be used at the high label rate for control and resistance management of powdery mildew. Availability is limited this year.
The chemical group 3 products Nova/Fullback are very effective. However, do not use them more than two times consecutively to avoid resistance development. 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.
Remember to treat young plantings because severe infections can reduce shoot growth, which is most concerning for young, non-bearing orchards.
Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.

Fire Blight Prevention

Recommendations:

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.
If interested in pinching buds on young trees the practice can begin around the bud separation stage when it's possible to avoid removing the terminal shoot. Pinching buds becomes risky as bloom begins because fire blight bacteria grow on the flower stigma and are expected to be present in high numbers in warm weather. Do not pinch flowers when tissues are wet. This practice is time-consuming and any remaining flowers are susceptible to infection.
Apogee/Kudos is first applied at 2.5-7.5 cm of shoot growth. The product takes 10 days to become active so for the maximum effect on fire blight suppression it may be applied before fire blight symptoms appear. The product is not systemic so good coverage with high water volume is required.

Please note that Apogee is being discontinued by BASF next year. Kudos is the same active ingredient and will remain available. BASF will continue to support Apogee that has been sold into the channel until all inventory is exhausted.

Apple and Pear – Fire Blight Blossom Blight (Advance Notice)

Fire Blight Biology
Open blossoms must be present for a blossom blight risk. Fire blight bacteria are transported from overwintering canker sites to open flowers by the action of insects and rain. These bacteria then reproduce on the stigma of flowers and are washed down into the base of the flower by a wetting event – a minimum of just 0.25 mm of rain or heavy dew – which then initiates an infection if adequate bacterial populations are present. An average daily temperature of at least 15.6°C is needed to establish infections and the infection potential rises with consecutive hours above 18.3°C. Blossom blight risk increases with warm temperatures between 23°C and 27°C, especially when occurring over consecutive days because this temperature range is ideal for bacterial reproduction. The Maryblyt model criteria is used to predict blossom blight infections.

Monitoring for Blossom Blight

This year, all NSFGA-owned weather stations are being used for industry monitoring and alerts. Those weather stations are located in the following communities: Atlanta, Aylesford, Grafton, Grand Pre (fixed on May 8, 2025), Melvern Square, Morristown, Moschelle, North Medford, Windsor, and Woodville.

If you would like to join the alert contact list, please let me know or sign up online.
Alerts will be delivered on weekends and holidays.
Short notice blossom blight alerts will be delivered directly to your email inbox. Periods with high fire blight bacterial populations are defined by Maryblyt as having an Epiphytic Infection Potential (EIP) greater than 100. Notifications will be sent as soon as it is evident that the EIP will approach 100 for apples and pears.
Please watch for and take note of your first blossom date which is the first flower that opens on your orchard.
Ideally you will monitor your own farm-specific conditions and improve your management decisions using PomeBlight that was developed for Nova Scotia apple and pear growers. Subscribe or renew your subscription here: www.farmdatatools.perennia.ca. A Quickstart video is available here. Contact me if you need a quick refresher or need help setting up. Run the model using your own temperature, rainfall, bloom and spray dates (industry alerts will offer limited scenarios).

Apple – Calyx/Blossom End Rot

Recommendations:

The only product with activity on calyx/blossom end rot is captan applied during full bloom. If applying Streptomycin with Agral 90 there is a risk of burn if using captan. Prioritize fire blight over blossom end rot. Blossom end rot might not be treatable this year.
Infections can occur in problem blocks as the pathogen can last in the soil for several years. The disease is most common on Paulared, Delicious, Cortland, Honeycrisp and McIntosh.
Keeping grass and dandelions mowed will allow the soil to dry and reduce the environmental conditions for spore ejection. Other broadleaf weeds are also a host of this disease so weed control prevents the build up of this pathogen.

Stone Fruit - Brown Rot

Fungicide protection from brown rot should be maintained during periods of warm and wet weather during bloom.
For plums, the use of Captan/Maestro for brown rot during the white bud stage through fruit set will also give some control of new black knot infections.
Rotating classes of brown rot fungicides is key to slow resistance development.

Insects

European Red Mite

Erika Bent with APM reports that egg hatch began in the Valley on the afternoon of Wednesday, May 7. The opportunity to apply oil has closed and the next opportunity to control European red mites will be by using summer miticides post-bloom.

Figure 5: European red mite eggs from before egg hatch to after egg hatch. Before hatching the eggs are red and round (left). After hatching the eggs are translucent (middle). The European red mite can be found on new leaf tissue (right).

Pre-Bloom Insecticides

Spring Caterpillar Complex (winter moth, green pug moth, eyespotted bud moth, speckled green fruitworm, obliquebanded leafroller)

Spring caterpillars have grown in size and are more easily visible without magnification than they were early last week but they are still less than 10 mm in length. The caterpillars can be found feeding in flower buds currently (Figure 6). Eyespotted bud moth is distinct because it has a brown body compared to the green/yellow shades of other spring caterpillars. Green pug moth will develop a dark reddish brown coloured stripe on its back. Note that there is a lower tolerance for winter moth than green pug moth because green pug moth do not feed directly on developing fruitlets.

Figure 6: Spring caterpillars on flower clusters. An eyespotted bud moth larva among chewed tissue and frass (top photos). Green pug moth larva in a flower bud with a dark reddish brown coloured stripe on its back (bottom photos). Photo taken on May 8, 2025.

When I checked for insect activity on May 8, I also found an example speckled green fruitworm and want to share its differentiating features. It has three pairs of jointed legs near the head end, one pair of fleshy legs at the rear end, and four pairs of fleshy legs in the midsection (Figure 7). They do not inch their back when they move and they can curl up when disturbed.

Figure 7: A speckled green fruitworm. They can curl up when disturbed (left). They do not inch their back when they move (middle). They have four pairs of fleshy legs in the midsection (right). Photos taken on May 8, 2025.

The key treatment stage for spring caterpillars is between first pink, bud separation, and full pink (Figure 8). By first pink the leaves have folded down and it gives some exposure of fruit buds to insecticides. By bud separation the caterpillars hiding within the bud clusters are even more exposed so treatments are more effective after the buds separate. Treatments should be applied pre bloom so the main tradeoff with waiting is that there is a narrow application window by the time full pink is reached.

Figure 8: The progression of bud stages from tight cluster to full pink. Observe how the buds become more open over time to expose where spring caterpillars are hiding.

Recommendations:

Scouting involves taking an acceptable sample size, identifying the insects present, and comparing incidence to economic thresholds. If you would like the detailed procedure please reach out to me.
Choose pre-bloom insecticides according to the pest complex on your scouting report. 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.
Treatments for spring caterpillars should not be applied too early because product must enter the developing flower clusters where the larvae like to feed to be effective. Treatments should be applied pre-bloom so target the pink stage.
If treatments for obliquebanded leafroller are required at pink, the treatments will also have some activity on winter moth and green pug moth.

European Apple Sawfly

Recommendations:

In orchards with a history of damage and high numbers of EAS catches, an application of a group 4 or group 28 product at full pink is recommended to control the adults prior to egg laying.
For organic management, Surround is registered for application at first detection and throughout egg laying.

Tarnished Plant Bug

Recommendations:

If history of tarnished plant bug damage indicates that pressure is moderate to high, an application of insecticide at pink is warranted. Treatment must be applied before bloom, not after. Best effect achieved when treated as close to bloom as possible.
Pyrethroids (group 3) and Closer/Cormoran (group 4) are registered for control.

Rosy Apple Aphid

Recommendations:

One rosy apple aphid is equivalent to a colony because the first generation are all female that give birth to living young. They have a preference for flower/fruit clusters.
Rosy apple aphids have emerged from eggs and the first generation are present (Figure 9).
Monitor for rosy apple aphid populations that exceed thresholds.
Treatment pre-bloom is ideal for good coverage before aphids curl leaves. Closer works well for aphid control.

Figure 9: Rosy apple aphid on a flower cluster (left). A close up of rosy apple aphid showing the mature aphid that is dark bluish grey in colour. Photo taken on May 8, 2025.

General Notes

If a pyrethroid is applied for tarnished plant bug at pink, it will also have activity on WM and GPM. Similarly, pyrethroids are expected to have some activity on EAS if being applied for other pests.
As a reminder, pyrethroids are best used at moderate temperatures (25°C or less) and are harsh on beneficial insects and predator mites. They should only be used where potential losses justify their application.

Blossom Thinning

Planning for a Growing Good Growers tailgate meeting is underway for a discussion about thinning next week. Stay tuned.

The caustic thinner ammonium thiosulphate (ATS) is the first chemical thinning opportunity of the growing season. ATS reduces pollen germination, interfering with fertilization.

Advantages:

May lead to increased fruit size and return bloom compared to later fruitlet thinning. ATS could be a good consideration for early thinning of small fruited varieties (e.g. Ambrosia and Gala).
The caustic activity of ATS does not depend on the temperature at application, unlike fruitlet thinners.

Cautions:

Beware that if the fire blight risk is high (infection pending a wetting event) an antibiotic is needed prior to ATS or wait until the risk has decreased.
You are thinning with an unknown crop load (before fertilization).
There is potential for foliar spray injury. If ATS is applied to dry leaves then there is less chance of injury. Some foliar and petal burn is normal and suggests the concentration is effective for thinning.
It can increase fruit russet so avoid sensitive varieties as a precaution.
Blossom thinning cannot compensate for a lack of bud removal during pruning.

Recommendations:

ATS can be applied towards the later part of full bloom (80-100% FB), at which point adequate pollination of king flowers has occurred. Do not wait much longer and especially don't wait until petal fall because it can be too late.
The goal is to apply ATS when the king flower has had enough time to become fertilized but prior to the lateral flowers becoming fertilized. For more accurate timing, consider that in order to become fertilized, a pollen grain must germinate on the stigma and grow a pollen tube to the base of the style to reach the ovary. In cool temperatures of 13°C, fertilization of open flowers takes 5 days and in warm temperatures of 24°C, fertilization takes 2.5 days. Therefore, time the ATS application for several days after the desired percentage of bloom has opened.
In Nova Scotia, ATS has been used at 5.5 L in 100 gal/acre (13.6 L ATS in 935 L/ha). The concentration is what matters for its activity so don’t concentrate it by spraying a lower volume. Keep records to learn from your results. If you are not familiar with the product, be conservative with the rates, use it on a small area first, and talk to someone with experience about rates.
Remember, ATS is NOT recommended for defruiting young trees. In order to eliminate all blossoms, the ATS would need to be applied multiple times to target flowers that open at successive times. The frequent number of applications would increase the risk of foliar spray injury. The leaves of young trees are also very tender.

Horticulture

Pollination

Consider plans to move honeybees into the orchard for pollination when king flowers open. Bee activity has appeared slow this year so if you are able you may consider a higher density of hives.

Grafting

There are reports of bark slipping and grafting has begun.

Mowing

Keeping the orchard floor cover mowed pre-bloom will minimize dandelion flowers that attract bees, which increases the safety of pre-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.

Pruning and Training

Established trees are best when pruned prior to bloom unless you wish to reduce vigour.
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.
Glyphosate and 2,4-D require daytime highs of 10°C-15°C after a night above 3°C to have good activity and weeds must be actively growing.
In young plantings, weed control is essential. Local research showed that by year 4, a weedy planting was 39% the trunk cross sectional area of a hoed comparison. Trees planted this year before May 8 would have received a good settling rain and you may consider a residual herbicide before the next rain.

Fertilizing

Foliar nutrients to correct nutrient deficiencies:

Boron: Applied pre-pink. Do not use water soluble pesticide bags in a tank mix with boron and rinse the tank well before and after boron. Do not use boron with oil or Epsom salts.
Magnesium: Epsom salts are applied starting at pink. Do not use with oil or boron.
Nitrogen: Urea may be used from pre-pink to mid-June as a nitrogen supplement. Sprays near bloom give a boost of nitrogen when it is needed most. Urea used from tight cluster to mid-July can remedy a nitrogen shortage.
When foliar nutrients are applied in slow drying conditions, about 40% is absorbed in 6 hours. When applied in dry conditions, about 75% can be lost in 48 hours. Foliar nutrients are not well-absorbed at below 10°C.

Nursery Trees

Monitor for tarnished plant bug and green aphids.
Consider staking soon to prevent blowouts. Even if not tied, the rod acts as a physical barrier to mechanical injury.
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!

Planting Trees

Tree planting has been delayed by wet weather. Trees are best planted soon so that they receive the benefit of early season rains to water them in before dry summer weather.
The length of the rootstock that is above ground level will influence tree growth. Tree size diminishes as the rootstock portion above ground increases. Trees should be planted so that the graft unions are at a uniform height of 8 to 10 cm above the soil line after stomping into the ground.

Events and Notices

Provincial Programs Open

Department of Agriculture 2025-26 Program guidelines and application forms are available. Please visit novascotia.ca/programs for more information. The Advancing Clean Technologies for Agriculture Program guidelines and application form will be available at a later date. Please contact Programs or your nearest Regional Office for more information or for assistance in completing your application. Please note: Information that describes a return on investment is considered valuable.

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: Keith Fuller, Colin Hirtle, Harrison Wright, Larry Lutz, Kari Brown, Suzanne Blatt, Joan Hebb, Ariana Willick, Ian Willick, Heather Rand, Danny Davison, and Shawkat Ali.

Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.

Pages

Orchard Outlook Newsletter Vol. 25, No 5

Tuesday, May 13, 2025

Table of Contents:

Weather

2025 Degree Day Accumulations

Bud Development

Apple Buds

Pear and Stone Fruit Buds

Diseases

Apple – Scab

Recommendations:

Apple – Powdery Mildew

Recommendations:

Fire Blight Prevention

Recommendations:

Apple and Pear – Fire Blight Blossom Blight (Advance Notice)

Apple – Calyx/Blossom End Rot

Recommendations:

Stone Fruit - Brown Rot

Insects

European Red Mite

Pre-Bloom Insecticides

Spring Caterpillar Complex (winter moth, green pug moth, eyespotted bud moth, speckled green fruitworm, obliquebanded leafroller)

Recommendations:

European Apple Sawfly

Recommendations:

Tarnished Plant Bug

Recommendations:

Rosy Apple Aphid

Recommendations:

General Notes

Blossom Thinning

Horticulture

Pollination

Grafting

Mowing

Root Pruning

Pruning and Training

Weed Management

Fertilizing

Nursery Trees

Planting Trees

Events and Notices

Provincial Programs Open

Pest Management Guide

Blog Archive