Orchard Outlook Newsletter Vol. 22, No 16

Wednesday, August 31, 2022

Today's newsletter reviews disease pressure and continues with preharvest recommendations. Note that heat accumulated so far is still above average and may contribute to earlier harvest periods. Learn tips about getting a valley-wide view of the weather. Review apple scab and fire blight disease pressure from the season and be reminded of fungicide preharvest intervals. Finally, take a look at leaf pruning.

Table of Contents:

  • 2022 Degree Day Accumulations
  • Using the Cape Breton Mesonet Website for Weather Comparisons
  • Review of apple scab
  • Review of fire blight
  • Review of powdery mildew

Pest Management Guides 2022

Events and Notices

  • Nova Scotia Programs
  • Farm Transition Seminar Series from Farm Credit Canada


2022 Degree Day Accumulations

Jeff Franklin observes that, "Daily temperatures have been average to above average for most of the growing season. Temperatures for the month of June were near normal but late July and all of August have been well above average." In terms of degree days, it is therefore not surprising that the cumulative degree days are above the 10-year average for base 10°C heat units (Figure 1). The heat accumulated so far may contribute to earlier harvest periods but check your records from similar years such as 2010, 2012, 2013, and 2021 for guidance. My apologies that no degree day figure is provided this week but one will be included in the next update.

Using the Cape Breton Mesonet Website for Weather Comparisons

The Cape Breton Mesonet has recently undergone some excellent changes that help us get a big picture of weather events throughout the Valley. The website offers a map of the province with approved Davis weather stations. It is an interactive map where you can change what appears on the map by clicking the icons on the left side of the screen.
  • 'Layers' allow you to choose important data like temperature and wind, humidity, wind streamlines, and daily rain. Storm rain is especially interesting because it is the rain total of a rain event that begins with two tips of the rain spoon and ends when there have been 24 hours without rain (Figure 1).
  • Within layers and under the heading 'Extremes' you can load daily high or low temperatures or wind gusts across the Valley (Figure 2).
  • Below the layers icon is a calendar icon for 'History' that lets you choose a date in history to explore using the layers mentioned above.
  • The next icon is the 'Extra Functions'. Here you can access regional summaries such as the 10 NSFGA stations.

Figure 1: Using Layers and History on the Cape Breton Mesonet website to show the quantity of storm rain received throughout the Valley on August 14, 2022.

Figure 2: Using Layers on the Cape Breton Mesonet website to show today's extreme high wind gusts throughout the Valley as of late morning.

2022 Review of Disease Pressure

Review of Apple Scab

The infection periods for the 2022 season are summarized in Table 1. Above-average temperatures in early spring led to early maturing ascospores and wetting periods produced infection events that occurred roughly every week.

All scab infection events are reason for protection but, in particular, the event on May 15/16 was a notable risk period because up to 40% of total spore load could have matured since the last infection and new tissue had developed in the meantime. Other infection events in May also had significant spore load. This season a total of 9 primary infection events were recorded, which is slightly less than has been typical in recent years.

Secondary scab infection events were also ongoing and can occur up until harvest time, therefore any orchards with scab should continue regular fungicide sprays until preharvest intervals no longer allow their application. August fungicide applications are also used to prevent summer fruit rot diseases from showing up at harvest.

Table 1: Summary of apple scab primary infection events recorded in Kentville in 2022, based on the Modified Mills Table and assuming a green tip date of April 17.

Review of Fire Blight

The first blossoms in the Valley opened around May 14 with early regions in full bloom around May 23. A heat wave created a high risk of fire blight blossom infection during a critical period of bloom throughout the Valley. 
  • According to the Maryblyt model, EIP values approached the threshold on May 16-17 in a few regions. 
  • High EIP values were recorded on May 22 for most regions. Bacterial populations built rapidly in a single day during high forecast temperatures. Even new blossoms that opened on May 22 and that were colonized by bacteria were susceptible to infection. Only blossoms open at the time of an antibiotic spray are protected from infection.
  • High EIP values were recorded on May 29-30 for most regions. Antibiotic application was a juggle with winds, changing temperatures, and changing rain risk.
  • The EIP was again high during periods in mid- and late-June when young plantings were in bloom. 
  • Symptoms of early blossom infections began to appear around June 12. Blossom infections developed where protection was not achieved.
  • Trauma blight was a risk after very isolated hail on June 18. 

Fire blight pressure was certainly felt this year. Depending on the situation, infections seemed to arise where protection was not applied (usually less susceptible varieties), near festering infections from last year, coverage on only every second row, and poor coverage during full bloom. 

Reminders about Fungicide Preharvest Intervals (PHI)

Table 1: Fungicide products for control of summer diseases listed from longest preharvest interval to shortest preharvest interval. Includes notes about diseases controlled and re-entry intervals (REIs).

Preharvest Recommendations

Refer to the August 9th Orchard Outlook for more information regarding late season diseases and harvest fruit quality including topics on diseases, disorders, and Retain/Harvista.

Leaf Pruning

Some folks have chosen to remove leaves by hand on blocks that have struggled to get enough red colour. The practice is time consuming so it seems doable on early varieties but less likely on later varieties when harvest is well underway. If you are considering hand pruning leaves, here are some tips from local experience:
  • Take a handful of leaves near the fruit and cut them off with trimmers. Trimmers as opposed to pulling leaves avoids shaking off fruit or removing next year's buds. 
  • Save time by focusing on the lower canopy that is within reach and already exposed to less sun. 
  • Estimate the time commitment by timing how long it takes to do 10 trees and then average it by tree. 
  • Prune leaves within the 2 weeks before harvest.
  • Try to do the leaf pruning when there are 2 days of overcast weather in the forecast to prevent sunburn.
  • It is not yet known if leaf pruning influences winter hardiness. Limited leaf removal is not expected to have a big influence.
Figure 3: Leaf pruning by hand using trimmers shown on the early variety Minneiska as an example.

For more reading, here is research on the topic by Cornell University, "Using pneumatic defoliation to improve fruit color and quality in apple: A follow up from the International Tree Fruit Association Annual Conference." Their research suggests that hand pruning leaves or pneumatic defoliation result in about 90% of apples with more than 33% red colour compared to only 53% of apples on untreated trees.

Pest Management Guides 2022

All changes new to 2022 are made in red text directly on the guides. The information on all changes was summarized in a blog post on April 8th.

Events and Notices

For upcoming events, visit the ‘Events’ tab on the NS Tree Fruit Blog. Specific events will be described here when available.

Nova Scotia Programs

  • Soil and Water Sustainability Program - Helps farmers mitigate on-farm environmental risk for soil and water as identified in their individual Environmental Farm Plans that accelerate environmental farm stewardship in Nova Scotia. The deadline for applications is September 15th, 2022. Visit https://novascotia.ca/programs/.

  • Limestone Trucking Assistance Program – Aims to help Nova Scotia farms defray the cost of trucking limestone to give equal opportunity in neutralizing the acidity of the soil on agricultural land and improve production efficiencies. The deadline for application is September 1, 2022 (this Thursday). Visit https://novascotia.ca/programs/.

Farm Transition Seminar Series from Farm Credit Canada

Join Farm Credit Canada for a 9-part virtual event series on farm transition. Hosted by FCC Business Advisors and transition experts, each month will feature a new topic, highlighting a different step in the process.  Registration at their website.

Can’t attend a live event? No problem – check back to watch the recordings at your convenience!

  • September 20, 2022 – Value, vision, and goal setting - a farm transition powerhouse
  • October 11, 2022 - Building a farm transition team – how to find the right fit
  • November 8, 2022 - Will and estate planning: The key to any successful farm transition
  • December 13, 2022 - Creating a business plan that fits your farm transition vision
  • January 10 , 2023- Handing over the keys: Transferring knowledge in farm transition
  • February 14, 2023 - Unlock your inner CEO: Leading a successful farm transition
  • March 14, 2023 - Review, revisit, repeat: Keeping your farm transition plan alive

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

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