Today's newsletter reports the appearance of green tissue on early varieties in early regions. On Sunday/Monday it was unlikely that an apple scab infection event occurred because of cold weather conditions. Monitor weather conditions before applying copper or oil to green tissue because this week there are risks of hard frosts that could result in injuries. The weather this week is cold and is not ideal for application of glyphosate. However, this week may be a good opportunity for application of granular nitrogen fertilizer, ensuring it is present for distribution to the root zone in the next good rain event. Many thanks for the ongoing commitment of the Orchard Outlook Committee members.
Table of Contents:
- 2026 Degree Day Accumulations
- Soil Temperatures
- Apple Buds
- Pear and Stone Fruit Buds
- Critical Spring Temperatures for Reference
- Apple - Scab
- Fire Blight Sanitation
- Stone Fruit - Black Knot
- Delayed Dormant Oil - Cautions and Considerations
- Scale Insects
- Efficacy of Herbicides
- Crop Safety of Common Herbicides
- General
- Pruning
- Fertilizing
- Liming
- On-Farm Nursery
- Nutrient Management Planning Web Series
Weather
2026 Degree Day Accumulations
The cumulative degree days are in between the 5- and 10-year averages (Figure 1). Degree days accumulated more quickly over the last week due to above-average temperatures.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to April 13 for the past 17 seasons. Provided by Harrison Wright (AAFC Plant Physiology).
- Approximately 9% less plant development heat units compared to the 5-year average, and 11% more compared to the 10-year average.
- Approximately 7% less plant development heat units compared to 2025, and 8% less compared with 2024.
- Approximately 13% less insect development heat units compared to the 5-year average, and 7% more compared to the 10-year average.
Soil Temperatures
Currently, the soil temperature at 35 cm deep is around 8°C (Figure 2, red line). The soil temperature is relatively warm when compared with the 10-year average. Root growth usually begins where soil temperatures reach around 9 to 10°C. Typically 10°C is reached in early to mid-May. New root growth is white or tan coloured and succulent. Ideally granular nitrogen fertilizer will be applied early so the next rain event will make nitrogen available by the time of new root growth.
Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2021 to 2026. Provided by Jeff Franklin(AAFC). Each year is represented by a colour and the 10-year average is the black dotted line.
Bud Development
Apple Buds
This year's green tip prediction was a close predictor of field observations of green tip, especially in a year like this when cumulative degree days are close to average. Field observations of green tip on April 18 and 19 on early varieties in early regions are close to the average date of bud break of April 20.
An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on April 20, the Idared buds were at 50% green tip, Honeycrisp was at late scale separation and Ambrosia was at early scale separation (Figure 3). Honeycrisp was considered to be at late scale separation overall because some buds were showing green tissue but had not yet reached the majority. No green tissue was observed on Ambrosia yet.
Figure 3: Bud development in an early region on Middle Dyke Road in Kentville on April 20. Shown from left to right: Idared, Honeycrisp, Ambrosia.
Pear and Stone Fruit Buds
Critical Spring Temperatures for Reference
Freezing temperatures of -7°C are forecast by Environment Canada for this evening. The critical temperature for frost damage in apples during the green tip stage -7.8°C at which point 10% injury could occur. Bud injury is most likely on the lower canopy of the tree, on the king fruitlets, and in low lying areas or where cold air accumulates. More extreme temperatures of -12.2°C would cause 90% bud damage.Based on the stages reported in this newsletter, peaches are susceptible to 10% bud damage at temperatures lower than -6.1°C and European plums at -10°C.
Wait 24 hours after freezing temperatures to assess buds. Injured buds have signs of browning and healthy buds are fully green. Apple trees usually set too many fruit so if the bud injury is minor then there will be plenty of buds for setting a crop.
Diseases
Apple – Scab
For industry monitoring purposes, a green tip date of April 19 will be used for predictions of ascospore maturity this year. An apple scab infection event has not yet been recorded. The environmental conditions for an infection are listed in the Modified Mills Table.What was the risk of infection from the rain on Sunday night, given the presence of green tissue? The model of ascospore maturity says that roughly 1.1% of ascospores were mature by Sunday. However, the rain started in the dark and most ascospores need sunlight for spore release. Research suggests that spore release in the dark is only 2% of mature spores, meaning 2% of 1.1% = 0.02%. Spore release in the dark can matter in a high inoculum orchard but the risk is minimal in orchards without a recent history of infections. Therefore, most of the mature 1.1% of spores were released at sunrise on Monday morning. Monday was cool with an average temperature of 4.9°C after sunrise. A light infection was unlikely because leaves would have needed to stay wet for 26 hours after sunrise.
Recommendations:
- Green tissue should be protected with fungicide prior to the first predicted infection event. When the first infection event will occur is currently unclear.
- Depending on the forecast you monitor, there are chances of light showers this week. Given the cold conditions forecast for this week, infections would only occur after prolonged leaf wetting (greater than 20 hrs).
- Be ready to apply your first protectant fungicide to brand new tissue. If you are relying on the forecast, monitor it carefully. Warmer and wetter conditions than forecast could result in infection. As of today, no infections are forecast for this week. Don't let your guard down though!
- According to the cool forecast, ascospores are expected to mature slowly at a rate of 0-0.3% per day and by Sunday about 2.0% of total ascospores are mature, with 0.9% available since the last release.
- Reapply protection on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
- Good early-season fungicide options:
- Mancozeb products (manzate, penncozeb, dithane) are compatible with oil. They may be applied at up to 24 kg/ha/year whether that is up to 4 full-rate applications or up to 8 half-rate applications. The re-treatment interval is 7 days and the re-entry for pruning is 12 hours.
- Scala + half rate group M performs well in cool weather but needs tissue for uptake so likely best used as a second spray. Use before powdery mildew risk period because it has activity on scab only. The re-entry for pruning is 12 hours.
- Copper Spray + half rate mancozeb product should only be considered if there is less than 1/4 inch green tissue. Do not apply if frost is expected. Copper does not redistribute in rain so mancozeb is recommended to improve protection. Do not apply before heavy rain.
- Captan/Maestro and Folpan/Follow should be avoided within 7-14 days of an oil application. If you are not applying oil for European red mite, then these products can be used for early black rot management in high pressure situations. The re-entry for pruning after Folpan/Follow is 12 hours, and for Captan/Maestro is 4 days for low density and 6 days for high density.
- Allegro/Vantana/Downforce can be used within 1-3 days of oil. The re-entry for pruning is 24 hours.
- Buran is used post-infection only.
- Early in the season, there is no need to control powdery mildew so products with activity on powdery mildew can be saved for application at half inch green.
Fire Blight Sanitation
The goal of copper application is to cover the bark with copper to reduce the population of bacteria on plant surfaces that arise from bacterial ooze around the pink stage. The copper treatment will reduce the initial inoculum and limit the spread of fire blight bacteria to blossoms or wounded tissue on the tree but does not replace the need for blossom blight management. The copper sanitation strategy is most effective in blocks that had fire blight cankers in the previous two seasons.
Recommendations:
- Please note that leaf tissue injury could occur when copper is used alone or combined with oil when hard frosts/freezing temperatures occur, so proper timing is key.
- This week there are risks of hard frosts and risk of copper injury.
- A copper application is recommended when buds are at the green tip stage and no later than 1/4 inch green for fresh market varieties, after which phytotoxicity becomes a problem. Processing varieties where russet is tolerable can be treated later as well as nonbearing trees.
- Monitor the weather for a treatment opportunity. If the weather warms, the treatment opportunity could move quickly. Prioritize blocks with a recent history of fire blight.
- Copper will provide some fungicidal activity on apple scab but does not redistribute in rain so use a mancozeb fungicide as well if possible.
- A fixed copper product such as Copper Spray Fungicide (50% copper oxychloride) is recommended because it is resistant to being washed off bark surfaces by rain.
- Copper can be applied as a tank mix with 0.5% by volume (5 L in 1000 L) dormant oil to increase adherence. Apply in a high water volume to cover plant surfaces. In other words, coverage is very important and a concentrate volume applied to every other tree row would not provide enough coverage.
- Do not use dormant oil within 14 days of Captan or within 48 hours of freezing temperature.
- Cankers are visible now 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.
Stone Fruit – Black Knot
Recommendations:
- Prune limbs 15 cm beyond the knot and destroy knots (burn or flail mow).
- Remove knots before bloom. New shoots are susceptible to infection risk during active shoot elongation. Most infections are believed to occur just before or during bloom, or after petal fall.
- Removing the fruiting bodies will not eradicate the fungus in the orchard but it will help keep the pressure down.
- Flag wild trees surrounding the orchard that might also carry knots and remove them when time allows.
Insects
Delayed Dormant Oil - Cautions and Considerations
- 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. This week there are risks of hard frosts and risk of oil injury.
- For varieties with Delicious parentage (Ambrosia, Gala, Delicious), early applications of oil prior to tight cluster are less likely to result in bark blistering.
- Oil should NOT be applied to young trees.
- Consider the greater water volumes needed for large canopy trees that have not been pruned yet versus trees that have been pruned. Apply thorough coverage of the bark that is appropriate to the orchard situation.
Scale Insects
The best time to target scale is ideally just before the tree breaks dormancy or with a delayed dormant spray of oil by green tip. The treatment opportunity is narrowing and oil should be avoided on green tissue for the next few days due to the risk of freezing temperatures.
The timing for targeting scale is not similarly effective for mites. The timing for mites is geared toward egg hatch, which is after bud break and closer to tight cluster. Target your oil application for the more important pest issue.
Weed Management
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. Currently there is not adequate rain in the forecast for activation of residuals.
- 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. Activity is best when applied from noon to 6 PM. This week the weather looks too cold for good efficacy.
- 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.
- Treat grasses early in their growth stage for best control.
Crop Safety of Common Herbicides:
- Note that residual herbicides can damage single tree replacements of young trees if the product is not registered for use on young trees. Keep this in mind if you are considering planting single tree replacements after the drought. Damage may occur by planting into soil with herbicide residue or by mistakenly applying new residual herbicide.
- Speaking of the drought, the following residual herbicides can persist longer than usual in extreme circumstances like drought:
- For Authority, instead of waiting the usual 2 years for reapplication, you should wait 3 years since your previous application. The label advises a 3-year replant interval under normal circumstances and extended an additional year to a 4-year replant interval after drought.
- For Chateau, the rotational interval is 1 year. However, the label also says, “After periods of extended drought longer rotational intervals may be needed.”
- For Alion, there is no specific mention of drought in terms of replanting, but waiting longer than 12 months might be advised.
- 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.
- 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
General
- Keep ahead of brush because the spraying season will begin soon.
- Remove tree guards to prevent trunk diseases.
Pruning
- Plan ahead and watch re-entry intervals for pruning activities when fungicide programs begin.
- 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.
- Consider prioritizing pruning in fire blight blocks to finish prior to tight cluster when cankers begin oozing. Cut out cankers, whether fire blight or other diseases.
- 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.
- Currently, there is no rain in the forecast but spreading granular fertilizer now will ensure it is present with time to dissolve and become available in the next good rain.
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.
On-Farm Nursery
- If planting bench grafts, it is best to wait for the soil temperature to be warm enough for bench grafts to grow. It is better to wait for warm soil than to let the grafts sit. Also, keep in mind that the new callus is susceptible to damage from freezing temperatures.
- 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.
Events and Notices
Nutrient Management Planning Web Series
Whether you're an agronomist, extension or industry professional, or interested in sustainable soil management, this series will give you valuable, actionable insights you can apply right away.
April 27 - Nitrogen management
May 4 - Phosphorus management
May 11 - Base cations
May 19 (Tues) - Manure and organic amendment management
Register online here to join!
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, Harrison Wright, Danny Davison, Joan Hebb, Ian Willick, Mathew Vankoughnett, Keith Fuller, Suzanne Blatt, Dustin MacLean, Colin Hirtle, and Shawkat Ali.
Edited by Michelle Cortens, Tree Fruit Specialist
Perennia Food and Agriculture Corp.
Perennia Food and Agriculture Corp.
