Orchard Outlook Newsletter Vol. 24, No 4

Today's newsletter discusses bud and tree observations that have been reported recently. We review the latest disease risks now that early fruit buds have reached the tight cluster stage. Please note that the rain in the forecast has the potential to produce a long-lasting wetting period that could lead to heavy apple scab infection of available spores. There are a few early notes about pre-bloom insecticides. Also, check out key takeaway messages from the tailgate meeting about weed management in young orchard. Thanks to the ongoing commitment of the Orchard Outlook Committee members.

Table of Contents:

Weather

• 2024 Degree Day Accumulations
• Soil Temperature
• Trunk Health

Bud Development

• Apple Buds
• Pear and Stone Fruit Buds

Diseases

• Apple - Scab
• Apple - Powdery Mildew
• Fire Blight Sanitation

Insects

• European Red Mite
• Looking Ahead to Pre-Bloom Insecticides

Weed Management

Horticulture

• General
• Pollination
• Grafting
• Mowing
• Notching for Blind Wood
• Pruning
• Fertilizing
• Liming
• Nursery Trees
• Planting Trees

Events and Notices

• Cover Crop Selection Tool
• Marbicon Inc. / Jim Jotcham Pesticide Exam Preparation Courses
• Resilient Agriculture Landscape Program

Online Pest Management Guide

 

Weather

2024 Degree Day Accumulations

The degree day accumulations beginning on March 1 are now slightly less than the 5- and 10-year averages (Figure 1). The degree days at base 10°C are below average and may suggest delayed insect activity.

A few successive evenings of temperatures below zero in April are leading to reports of minor freeze injury to buds. As we would expect, the injury is most common in low-lying regions on early varieties and the king fruit. I encourage you to check buds keeping in mind that green is good and brown is bad. Let crop insurance know of any suspected damage. Also, as we reach bud separation another sign of freeze injury is for king buds to have short stems.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 6 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

• Approximately 3% less plant development heat units compared to the 5-year average, and 2% less compared to the 10-year average.
• Approximately 8% less plant development heat units compared to 2023, and 3% more compared with 2022.
• Approximately 18% less insect development heat units compared to the 5-year average, and 27% less compared to the 10-year average.

Soil Temperature

The soil temperature has increased over the last week to about 9°C, the temperature at which new root growth is expected to begin. With some rain in the forecast, granular fertilizer can start to become available for immediate uptake.

Figure 2: Soil temperatures at 35 cm depth at the Kentville Research Station from 2020 to 2024. The current year is shown in red. Provided by Jeff Franklin (AAFC).

Trunk Health

The last few years in 2022 and especially in 2023 we expected to observe trunk injury as a result of extreme winter temperatures. The incidence of trunk injuries has increased in recent years and depending on the situation the trees either continued to decline or splits healed over. Varieties that are especially sensitive to extreme temperatures are Northern Spy and Gravenstein. Bark splitting historically shows up on thin bark varieties like Gravenstein and Gala.

This note is here to remind you to monitor for trunk health because new trunk issues have been observed early this spring. The exact cause is unknown but there are a few possibilities. Fluctuating growth conditions can cause bark to split, such as in the 2023 season when a drought was followed by excessive rain. This past winter did not have extreme temperatures however the recent symptoms may be related to carryover damage from the polar vortex in 2023. Reports and research on winter injury suggest that not all effects are quickly realized and may linger for several years while being accompanied by other stressors.

Figure 3: Over the last several years the trees have been subjected to extreme temperatures and fluctuating moisture conditions so we may continue to see signs of damage. Monitor for trunk injury and please let me know if you're seeing similar signs.

Bud Development

Apple Buds

An early region on Middle Dyke Road in the Kentville area is monitored to guide this newsletter. Yesterday on May 6, the Idared buds were at tight cluster, Honeycrisp was at late half-inch green and Ambrosia was at late half-inch green (Figure 4). Each year I am more curious about the vegetative growth, especially if we want to target the early timing for Apogee/Kudos. An early measurement of the vegetative growth shows it currently ranges in length from 0.5 to 2.0 cm (Figure 5).

Figure 4: Fruit bud development in an early region on Middle Dyke Road in Kentville on May 6. Shown from left to right: Idared (tight cluster), Honeycrisp (late half-inch green), and Ambrosia (late half-inch green).

Figure 5: Vegetative bud development in an early region on Middle Dyke Road in Kentville on May 6. Shown from left to right: Idared (2 cm), Honeycrisp (0.5 cm), and Ambrosia (0.5 cm).

Pear and Stone Fruit Buds

Yesterday on May 6 at an early region in Greenwich, the pear buds were at bud burst, peach was at first pink, European plum was at green cluster, and sweet cherry in Kentville by S. Blatt was at tight cluster (Figure 6).

Figure 6: Bud development in an early region in Greenwich on May 6. Shown from left to right: pear (bud burst), peach (first pink), European plum (green cluster), and sweet cherry - Kentville (tight cluster).

Diseases

Apple – Scab

Table 1: Apple scab infection events in Kentville from April 30 to May 7, 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 Saturday, April 15th. 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:

• Is this déjà vu? The recent wetting event was a very similar situation to last week's event so the message stays the same. It is tricky to pinpoint exactly when leaves in different microclimates for different varieties become dry so for borderline infections the only way to be sure is to stay covered. The risk is present because ascospores were mature and present for release.
• According to the forecast, ascospores are expected to mature at a rate of about 2.5% per day. By the start of the forecast rainfall on Friday an additional 11.1% of ascospores are expected to mature and available for release (seasonal total of 25%). The rain in the forecast has the potential to produce a long-lasting wetting period that could lead to a heavy infection of available spores. Do not wait for post-infection control of such a long-lasting infection.
• Manzate is a good choice as it can redistribute to new tissue during extended wetting periods. 
• Apply a protectant fungicide to green tissue prior to an infection event and reapply on a 7-day interval, with a shorter interval after wet weather (cumulative 1-2” rain) or rapid tissue growth.
• Folpan/Follow should NOT be applied between tight cluster and 30 days after petal fall to avoid fruit russeting.
• Remember that Manzate (mancozeb) products may be applied 4 times/ha/year, the re-treatment interval is 7 days, the REI for hand thinning is 35 days (12 hrs for all other activities), and the PHI is now 77 days.
• If you plan to use oil for European Red Mite control, Captan should be avoided within 7-14 days of an oil application.

Figure 7: When did leaves dry off on Monday? Do not rely on only leaf wetness sensors and be sure to check leaf tissues. On Monday, May 6 at 1:30 PM it was clear that Idared was still wet (left) but less clear for Honeycrisp (middle) and Ambrosia (right). Overcast conditions without wind led to slow leaf drying times.

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 the 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, if powdery mildew protection is not already applied it may be best timed after the wet weather to give you protection during warm and dry weather when powdery mildew infections are expected. As the forecast currently stands, 5 days worth of rain will mean that powdery mildew is likely not a concern until you are due for fungicide re-application anyway.
• Early regions might have already had an opportunity to apply protection given a few days of warm and sunny weather. Fullback and Nova are systemic and given a long drying of 24 hrs they should be well-absorbed into the plant.
• Application of a protectant mildew fungicide around the tight cluster stage prevents infections of leaf clusters from the overwintering infections. Timely application that prevents infections early in the season will reduce the risk of infections later. 
• 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.
• Practice resistance management:
• Powdery mildew: Group Ms do not have activity on powdery mildew so they will not help prevent powdery mildew resistance development. Products in the groups 3, 7 and 11 are registered for control of PM. Resistance to group 11 products was reported in a survey in 2013. Therefore, whenever the remaining groups 3 & 7 are used, careful consideration must be given to rotating the groups to slow resistance development. Avoid more than two consecutive applications of a single group.
• Scab: Although Group 3 fungicides Nova and Fullback are also labeled for apple scab, they are not expected to provide control because of resistance in the local scab population. Another product is required for scab protection.

Fire Blight Sanitation

Typically the ooze begins to appear between tight cluster and early pink. Initially the ooze is a watery light tan that darkens to amber. When the canker blight bacteria are active, water sprout shoots close to cankers will wilt. 

Recommendations:

• Cankers are not visibly oozing yet but are approaching the period of time when we would expect them to become active.
• 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.
• 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.

Insects

European Red Mite

A delayed dormant oil is effective at managing European red mite if monitoring indicates a treatable overwintering egg population. The oil is most effective when applied around egg hatch (typically around tight cluster and before pink) but if practical it may be applied earlier. As of today, Erika Bent, APM, reports that egg hatch has not yet begun in the Valley. Hatch is expected to begin soon so the opportunity to apply oil will soon close. 

European red mite eggs overwinter in the cracks on buds and spurs so adequate water volume is needed to reach all of the crevices. The oil treatment is not effective for rust mite or two-spotted spider mite.

Avoid oil if freezing temperatures will occur within 48 hrs and no captan within 7-14 days. Oil should not be applied to young trees at less than 3 years old, and the risk on varieties with Delicious parentage (Ambrosia, Gala) increases after tight cluster.

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. Choose pre-bloom insecticides according to the pest complex on your scouting report. Take note of the higher rate required for some pests. 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.

Spring Caterpillar Complex

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

Recommendations:

• 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. 
• Evidence of feeding includes tiny holes in new leaves and flower buds, and black specks of frass. Begin scouting procedures described in Perennia’s Best Management Practices or monitor your scouting reports for notes on WM, GPM, and other caterpillars for those with scouting services.
• Note that there is a lower tolerance for winter moth than green pug moth. Green Pug Moth do not feed directly on developing fruitlets.
• If treatments for OBLR are required at pink, the treatments will also have some activity on WM and GPM. 

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

Studies have shown maintaining weed free strips from bud break to 30-days after full bloom has the greatest impact on tree growth and yield. Timely herbicide application will ensure you make the most of the weed free window.

Recommendations:

• There is rainfall in the forecast that can activate residual 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. 
• Note that after the rainy period, applying Ignite when leaves are wet is relatively ineffective. Also use Ignite during hot days in full sun if possible.
• If you are preparing the ground for planting, note that a pre-plant glyphosate application should be made at least 3 days before tillage. This is especially important to target perennial plants like quack grass and especially in cool temperatures.
• Consider painting the trunks of newly planted trees white to prevent herbicide injury. Use a water-based white latex paint that may be diluted 50% with water.
• 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.
• If weeds are already present, add a post-emerge to a residual herbicide to achieve control.
• Post emergence herbicides are best applied on warm and sunny days. Glyphosate and 2,4-D require daytime highs of 10°C-15°C after a night above 3°C to have good activity. If using glyphosate alone, consider coarse droplets and low pressure to reduce drift.

Here are some additional takeaway messages from the Growing Good Growers tailgate meeting about weed management in young orchards with guest Sonny Murray:

• Understand and consider using more Venture for grass control in young orchard. Venture is slow to work (2-3 wks) but you can check for activity by removing the flag leaf on treated grass and examining the base of that shoot for rot.
• Add Prowl H2O or Dual II Magnum to improve your grass control spectrum. These pre-emerge products won’t work for bluegrass species however.
• Sinbar is good for pre-emerge grasses in young orchard.
• Lontrel is a great post-emergent for vetch, clovers, and sheep sorrel.
• Chateau has activity on Ragweed whereas Authority does not.
• Target some tough perennials in late November to early December when trees are dormant but while the ground is not frozen.
• Take note of weeds that are present in early spring. They are perennials and winter annuals that are ready to grow immediately come spring.
• Create a plan for the whole year. Put on residual products before weeds emerge and use the post-emerge products as backup.

Horticulture

General 

• Remove tree guards because otherwise they can trap moisture and encourage disease. 

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.

Notching for Blind Wood

• Notching and applying plant growth regulators (Promalin and MaxCel) is best done from green tip and up until bloom time. The ideal time is at the stage of half-inch green.
• Please note that the success rate of inducing a branch depends on the age of the planting. Applying a mist of plant growth regulators to the notched area can increase the success rate, namely for older plantings of up to 7 years of age.
• Notching is preferred over scoring. Scoring can oftentimes heal over and you lose the effect.
• The plant growth regulators work in cooler temperatures but warm temperatures at the time of application increase the response. For more information, see an article by MSU Extension.

Pruning

• Prioritize pruning fire blight-affected blocks before ooze becomes active for the season.
• Plan ahead and watch re-entry intervals for pruning activities. 
• 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 for vigorous Ambrosia to reduce its vigour.
• Mature blocks can be pruned later and are best when pruned prior to bloom unless you wish to reduce vigour.
• A handout for farm workers 'The Fundamentals of Pruning' was published this year.

Fertilizing

• Bud break to bloom is the ideal time for granular fertilizer application to maximize tree growth. When banding fertilizer in the tree row, calculate the area to be banded rather than the total field. Soil test recommendations usually assume the fertilizer will be broadcast across the field. What percentage of the total field area is being banded? Reduce your rate accordingly.
• 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 especially for sandy soils.
• If Honeycrisp is on the rootstock G.41 then potassium additions are discouraged.
• Target 10-16 inches of new growth on bearing trees each year. More growth is a sign of excessive nitrogen.
• 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 which often happens with Geneva rootstocks. If using M26 rootstock and tbuds, consider removing the root suckers slowly to avoid flooding the scion bud.

Planting Trees

• In most cases, the earlier a tree can be planted into friable soil the better. Conditions appear to be good right now for settling the soil around trees. There are likely fewer risks in planting early than late. However, if you are concerned that moisture is lacking, consider installing drip tape. Temperatures for root growth are right around the corner and the forecast for precipitation is unreliable.
• Remember the importance of soil preparation. Remove old roots and work to get a good soil tilth without sods and clods especially in the top 15 cm of soil.
• When trees are first planted they need a high level of soil phosphorus because roots are too poorly developed to forage for it. If phosphate is needed, diammonium phosphate (DAP) can be banded in furrow and incorporated. There is no need to apply phosphorus if a soil test shows P2O5 to be high, such as on land with a history of manure application.
• A new report has now been published by Perennia to summarize local research on, "Developing knowledge-based strategies to manage plant parasitic nematodes in Nova Scotia apple orchards."
• Remember to document the quality of purchased nursery trees with pictures and notes. Did trees dry out? Any signs of disease (cankers, crown gall)? How do the roots look (rinse and take a photo)? Notify the appropriate people of issues you notice. Record the date of planting. An issue that shows up after planting is much easier to diagnose or prevent given this information.
• 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.
• 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.
• Wait for a settling rain before applying a residual herbicide to young plantings.

Events and Notices

Cover Crop Selection Tool

Perennia has launched a NEW Cover Crop Selection Tool! on the Farm Data Tools website. This tool was designed to help producers make agronomic decisions on cover crops according to their goals. This new online tool will help you learn about cover crops that are suitable for your region and provide detailed information on planting, termination, traits, advantages and disadvantages for different species.

Marbicon Inc. / Jim Jotcham Pesticide Exam Preparation Courses

Marbicon Inc. / Jim Jotcham is offering another round of in-person exam-preparation courses (T2380). 

5 recertification points are available (you can only get credit for T2380 once).
The following locations are confirmed to date, with possible additional courses pending demand.
May 14 Tues – Berwick – Berwick Legion Hall, 232 Main St.
May 16 Thurs – Truro – Douglas St Recreation Centre, 40 Douglas St.
May 21 Tues – New Germany - Anglican Church Hall, 5311 Hwy 10.

The full course, preparing for the exam (all pesticide applicator categories), is $125.
Doors open at about 8:30. Instruction starts at 9:00. Expect to be done around 4:00-4:30.
For only 5.0 recertification points (T2380), the fee is $110 and finished by around 3:15 pm.
A manual is provided. Bring a pen or pencil. Food & drink is not offered. Bring your own or go buy it.

NOTE: Pesticide exams are normally written online, NOT at this course.
Contact NS Environment for further details on writing the exam.
A course is not required before challenging the pesticide exam, but it usually helps.

HST is included in the above prices.
Cash or cheques (payable to Marbicon Inc) or e-transfer (marbicon[at]eastlink.ca).
If paying by e-Transfer, please add a message (for who and for which course).
Pay at the door or by corporate/government purchase order.
Sorry, no Visa, MC, or Debit.

Contact Jim Jotcham at marbicon[at]eastlink.ca or at 902-538-7101 for more details and/or to pre-register.

Resilient Agricultural Landscape Program

The Resilient Agricultural Landscape Program helps to improve the environmental resiliency of agricultural landscapes by accelerating the adoption of on-farm land use and management practices that maximize benefits for the environment and society. Buffers and shelterbelts are listed in the program guidelines for 100% of the establishment costs up to $1,500/acre for creating or widening buffers. The maximum assistance is on a case-by-case basis. The application is due June 30, 2024. For more details, visit the NSDA Program page.

Online Pest Management Guide

Beginning this year, all of the pest management guides are available from an online tool. On the tool you will find guides for organic and conventional apples, pears, peaches/nectarines, plums, and sour/sweet cherries. You can search and filter the information and/or print. To help you navigate the guide, we have developed a brief tutorial video as well as a how to use guide.

The apple and pear guide have been fully reviewed. The stone fruit guides are currently under review (almost done!). I will post the growth regulator guide soon. This year is a transition year as Perennia has migrated all of the information to a new format and this tool will continue to improve as we actively work on it. Please stay tuned.

This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's participants: Larry Lutz, Jeff Franklin, Suzanne Blatt, Danny Davison, Ian Willick, Joan Hebb, Dustin MacLean, Shawkat Ali, Jill MacDonald, and Heather Rand.

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