In today's newsletter we review recent apple scab infections from prolonged wetting and the current conditions that are not conducive to powdery mildew infection. We look at intact eggs of European red mite among bud scales, suggesting why thorough coverage with oil is important and noting that egg hatch is expected to begin soon. We pull apart flower buds to put spring caterpillars under the microscope for a close look at brand new photos for reference. Insecticide application should wait until buds are separated to enter the developing flower clusters. 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 Sanitation
- Stone Fruit - Gummosis
- Delayed Dormant Oil - Cautions and Considerations
- European Red Mite
- Looking Ahead to Pre-Bloom Insecticides
- Spring Caterpillar Complex
- European Apple Sawfly
- Tarnished Plant Bug
- General Notes
- Efficacy of Herbicides
- Crop Safety of Common Herbicides
- Pollination
- Grafting
- Mowing
- Treatments for Blind Wood
- Pruning
- Fertilizing
- Liming
- Nursery Trees
- Planting Trees
- Provincial Programs Open
Weather
2025 Degree Day Accumulations
Precipitation accumulation this spring has not been exceptionally high but consistent rainy weather has occurred with wetting on 38 out of the previous 50 days. The recent rains are delaying tree planting.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 5 for the past 17 seasons. Provided by Jeff Franklin (AAFC Plant Physiology).
- Approximately 28% more plant development heat units compared to the 5-year average, and 33% more compared to the 10-year average.
- Approximately 29% more plant development heat units compared to 2024, and 47% more compared with 2023.
- Approximately 55% more insect development heat units compared to the 5-year average, and 42% 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 5, the Idared buds were at tight cluster, Honeycrisp was at early tight cluster and Ambrosia was at late half-inch green (Figure 2). Growth progressed quickly through 1.5 growth stages over the previous week. Development is now ahead of last year's photos that were taken around this time, due to the sudden growth.
Figure 2: Bud development in an early region on Middle Dyke Road in Kentville on May 5. Shown from left to right: Idared, Honeycrisp, Ambrosia.
Pear and Stone Fruit Buds
Yesterday on May 5 at an early region in Greenwich, the pear buds were at late bud burst, peach was at pink, and European plum was at green cluster (Figure 3). Orchard Outlook committee members also report that sweet cherry in Kentville is at late tight cluster.
Diseases
Apple – Scab
Table 1: Apple scab infection events in Kentville from April 29 to May 6, 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:
- The wetting period on April 30 was not long enough to cause infection according to my observations in the Kentville region.
- Altogether there was plenty of infection potential during the extended wetting period over the weekend. Rainfall totals over the weekend varied from 16 mm to 26 mm throughout the on-farm NSFGA weather stations in the Valley.
- There was sufficient product wash off and plenty of new tissue growth to warrant recovering for the upcoming extended 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 2-4% per day.
- Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
- If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.
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:
- You will not receive the full benefit of powdery mildew protection if it is applied immediately before heavy rain. Powdery mildew infections do not occur in wet weather because the spores do not germinate on a wet leaf surface. Rain also removes powdery mildew spores in the air and destroys spore-producing structures.
- Given the extended period of rain in the forecast, powdery mildew protection is best timed after the wet weather. As the forecast currently stands, 4 days worth of rain will mean that powdery mildew infections are not likely a concern until you are due for fungicide re-application anyway.
- If Fullback and Nova were applied during this short period of dry weather, they 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.)
- A program with two pre-bloom and one post-bloom fungicide for control of powdery mildew is needed in high-pressure situations.
- 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.
- The chemical group 3 products Nova/Fullback are very effective. However, do not use them more than two times consecutively to avoid resistance development.
- 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.
- 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 Sanitation
Recommendations:
- Cankers are approaching the period of time when we would expect them to become active and ooze. When ooze is active, 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.
- Cankers are currently visible before they become hidden by this year's foliage. Scout for cankers now.
- If in doubt, take it out! No cankers are helpful and they harbour diseases. If you need a second opinion, I can take a look. Cankers are especially risky in young orchards because they harbour the bacteria for new blossom infections that give bacteria rapid access to the leader of the tree. Consider completely removing young trees that have cankers.
- Copper can be applied to nonbearing trees and processing varieties where fruit russet is not a concern.
- 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.
Stone Fruit - Gummosis
Gummosis is an exuding of sap that is most evident early in the season as the sap starts to flow. The most common cause is Cytospora canker that infects through pruning cuts, sun scald injury, or cold injury. Personally I cannot attest to how much gummosis was present prior to the cold 2023 winter versus after but I would not be surprised if a higher incidence is observed in the years following the cold winter.
Recommendations:
- To reduce the incidence of re-infection, do not prune peach/nectarine, plum, and cherry in wet weather.
- Remove severely affected trees.
Insects
Delayed Dormant Oil - Cautions and Considerations
CAUTIONS: DELAYED DORMANT OIL
- When green tissue is present, do not use dormant oil 48 hours before or after freezing temperature. Oil that is applied before freezing temperatures breaks down and adheres to the plant tissues unevenly instead of the target insects. Also if the oil and water mixture freezes before it dries then the green tissue can be injured.
- For varieties with Delicious parentage (Ambrosia, Gala, Delicious), applications of oil at the tight cluster stage or later could result in bark blistering.
- Oil should NOT be applied to young trees.
European Red Mite
A delayed dormant oil is effective at managing European red mite if monitoring indicates a treatable overwintering egg population.Recommendations:
- As of Monday, May 5 I have not observed egg hatch and Erika with Agricultural Pest Monitoring has not observed egg hatch. Hatch is expected to begin soon so the opportunity to apply oil for effective results will soon close.
- Using oil is a helpful strategy to prevent ERM resistance development to available summer miticides.
- Early season oil is fully compatible with the beneficial predator typhs and will not interfere with biological control of mites.
- European red mite eggs overwinter in the cracks on buds and spurs so high water volume is needed to reach all of the crevices (Figure 5).
- The oil treatment is not effective for rust mite or two-spotted spider mite.
Figure 5: European red mite eggs are round and red. The eggs can be found on at least 2-year-old wood of small diameter. The eggs are found singly or in groups in and around cracks and crevices of spur wood and buds. Thorough coverage of the bark is important because the oil acts by smothering mite eggs. Photo taken on May 5, 2025.
Looking Ahead to Pre-Bloom Insecticides
Depending on the heat in the forecast, your region, and monitoring reports, the action period approaches during the pink stage.Spring Caterpillar Complex (winter moth, green pug moth, eyespotted bud moth, speckled green fruitworm, obliquebanded leafroller)
You've been asking for more insect content, and I hear you! Here is an update on the spring caterpillar complex observed from samples taken yesterday on May 5, 2025. And some brand new photos for reference!
Spring caterpillars become visible on flower buds at the tight cluster stage by opening the leaves and separating buds. The caterpillars are hidden among tightly held buds where they are currently protected from insecticide application. Scouting involves taking a sample of clusters to examine closely. Oftentimes the caterpillar feeding is immediately visible but sometimes it is not clear until you start to pull back the leaves. Evidence of feeding includes tiny holes in new leaves and flower buds, and black specks of frass (Figure 6). Peeling back the leaves and pulling apart the buds can reveal a small caterpillar. That's when you need to identify it from the list of culprits.
Figure 6: Spring caterpillars on flower clusters. A winter moth or green pug moth larva in a flower bud (left). An eyespotted bud moth larva among chewed tissue and frass in a flower bud (middle). A winter moth or green pug moth larva behind a leaf in a flower bud (right).
Be warned, these caterpillars are extremely small at the tight cluster stage. It takes a very keen eye to spot and identify them. You should expect to find caterpillars that are less than 10 mm in length, and in my examples in Figure 7 they are actually 3-4 mm long. To put this into perspective, one caterpillar can fit on the tip of a bud scale. You will need magnification to identify the species. If you are learning to scout, try sampling flower buds from a wild apple tree or an abandoned orchard that is unsprayed to find enough examples to help train your eye.
Figure 7: Spring caterpillars are less than 10 mm in length. A winter moth or green pug moth that is 3 mm in length (left). An eyespotted bud moth that is 4 mm in length (middle). A green pug moth that is small enough to fit on the tip of a bud scale (right).
There are key features that differentiate the caterpillars. Winter moth and green pug moth have three pairs of jointed legs near the head end, two pairs of fleshy legs at the rear end, and no legs in the middle (Figure 8). They are relatively slow moving and inch forward by arching their back.
The individual in Figure 8 was protesting the light I was shining on it and for a giggle, just imagine the photo on the right saying, "I'm a spring caterpillar, hear me roar."
Figure 8: Key features of caterpillars. An young overturned caterpillar (either winter moth or green pug moth) with the head end pointing down; showing three pairs of jointed legs near the head end, two pairs of fleshy legs at the rear end, and no legs in the middle (left). Another view of the three pairs of jointed legs near the head end (right).
However, early in larval development some of the key identifying features are not yet present (Figure 9). That's why I continue saying winter moth or green pug moth. Oftentimes you will not see photos of this young larval stage.
Figure 9: Young winter moth or green pug moth that do not have identifying features such as stripes to differentiate them.
Figure 10: Green pug moth develops a dark reddish brown colour stripe on its back (left). Eyespotted bud moth has a brown body (right).
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.
- Pyrethroids (group 3) and Closer/Cormoran (group 4) are registered for control.
General Notes
- Monitor for rosy apple aphid populations that exceed thresholds when aphid stem mothers start producing offspring. Treatment pre-bloom is ideal. Closer works well for aphid control.
- 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.
Weed Management
Recommendations:
This week consider...
- There is good rainfall totals in the forecast for activation of residuals.
- Do not apply Ignite to wet leaves.
Efficacy of Herbicides:
- Most residual herbicides need about 1/2" of rainfall within 7 to 14 days of application to deliver product to the germination zone and to activate the chemical by putting it in solution.
- 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.
- Perennial weeds may be targeted in spring when new perennial plants are at the seedling stage. Other timings are spot sprays at the early flowering stage or during fall re-growth after a minor frost. Glyphosate and group 4 products are systemic and work on certain perennial plants.
- If weeds are already present, add a post-emerge to a residual herbicide to achieve control.
Crop Safety of Common Herbicides:
- In the USA, there are concerns about Ignite causing bark cracking. The specific risks are yet to be defined but just be cautious that Ignite is not sprayed onto or drifts onto young tree bark.
- Chateau should not be applied after budbreak unless application equipment is shielded to prevent crop injury.
- If you are taking out orchard within the next 2-3 years for replanting, avoid applying residual herbicides. The Alion label says to allow at least 12 months from last application to replanting an orchard.
- Note that residual herbicides can damage single tree replacements because the trees are not yet established for longer than 3 years.
- When mixing residual herbicides, agitation is important to keep the product in solution. If the herbicide settles in the tank then it can be delivered in a high concentration and possibly result in crop injury.
Horticulture
Pollination
- Consider plans to move honeybees into the orchard for pollination when king flowers open.
Grafting
- Bark typically slips from pink to bloom but can be checked early if you plan to get a head start.
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.
Treatments for Blind Wood
- Scoring and notching above paradormant buds should be completed by bloom time.
Pruning
- Ensure that youngest blocks are pruned first so growth is directed into desirable leader and terminal extension. Prioritize high value trees and then return to low value areas.
- Pruning may be delayed closer to bloom for vigorous Ambrosia to reduce its vigour.
- Mature blocks can be pruned later and are best when pruned prior to bloom.
- A handout for farm workers 'The Fundamentals of Pruning' is available in English and Spanish.
Fertilizing
- Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth.
- If leaf and soil samples show that phosphorus and potassium are adequate there is no need to apply phosphorus and potash. Granular formulations with 0.3 boron are encouraged for sandy soils.
- If Honeycrisp is on the rootstock G.41 then potassium additions are discouraged.
- Target 10-16 inches of new growth each year. More growth is a sign of excessive nitrogen. Keith Fuller and Michelle are working on an updated factsheet for nitrogen fertilizer recommendations to be available next year!
- 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.
Liming
- Lime soils prior to planting an orchard with rates according to your soil report. Early spring is an option but fall can be a more practical time to apply lime to a new site and lengthen the time for acidity to become neutralized.
- Orchard maintenance with surface applied lime twill take a number of years to adjust pH of the soil profile so it is best to apply annually or biannually where needed. If soil testing for pH, measure during the same time each year (August) as pH can change over the growing season.
- The provincial limestone trucking assistance program is open.
Nursery Trees
- Rootstocks that were chip or t-budded last year may have buds pushing. Cutting rootstock tops early can help to prevent the rootstock from overpowering the new buds. Rods may also be put into place early to avoid knocking off buds if done at a later timing.
- Early application of granular fertilizer can minimize the risk of leaf burn. Otherwise, granules can get trapped and sit in new leaf tissue that is close to ground level.
- If growing your own trees, criticize their quality and don't plan to plant 100% of the trees. Planting small (<4 ft), weak trees will delay production. Trees are typically small for a reason and will continue to be weak trees. Commercial nurseries grade their trees and build in the cost of discarded trees so the same approach is recommended for on-farm nurseries. Tree losses of at least 10% are common.
Planting Trees
- Repair drainage before trees are planted to prevent underlying drainage issues that would influence the planting for the rest of its life.
- 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.
- Avoid letting trees dry out. About 40% of trees can die from drying out, and surviving trees grow slowly. Survivors of 15-minute dry winds recover by year 3. Survivors of 45-minute drying winds still don't grow well by year 3. Bundles of trees sitting in water awaiting planting can asphyxiate, especially in stagnant water and/or warmish water.
- Remember to document the quality of purchased nursery trees with pictures and notes.
- Wait for a settling rain before applying a residual herbicide to young plantings.
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: Suzanne Blatt, Joan Hebb, Ariana Willick, Ian Willick, Heather Rand, Jeff Franklin, Danny Davison, and Shawkat Ali.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
