There have been many developments in how to target your crop load over the past few years. Extensionists and researchers are working hard to make this critical task as simple as possible for apple growers. This article will go over the resources at your disposal to make more informed data driven decisions regarding your thinning strategy.
Overview
These actions, tools and additional resources can be used in unison to give you a better feel for what works with you and your crew. Please take these into consideration and apply them in the orchard to get a better idea of your thinning strategy. The more tools you try, the more familiar you are with what you have on hand, allowing you to be more adaptable for the ever-changing season.
Actions
Record Keeping
- This is a critical step to adjust your thinning year to year to get a consistently good crop from the ever-changing apple landscape (weather, climate, pollination etc.)
- Keep track of growth staging (bud break and bloom are critical), target crop load, thinning strategies, weather, yields etc.
Calculating Your Target Crop Load
- Whether it be per acre, per tree or per branch – be sure to have an idea of what you want your expected yield to be
- This could be based on your market:
- Is there an ideal size or ideal volume that is expected?
- Is there a certain price point you want to reach?
- Would a larger fruit be worth the decrease in volume? Which is more important and/or what is the balance of volume to size that makes sense for your operation?
Precision Pruning
- Although time consuming in the beginning, once you have the experience and are comfortable with pruning to a certain bud count, this strategy can pay off year to year.
- This is suggested to be done in the winter, but I want to highly stress the importance of checking the forecast when dormant pruning. Fluctuations in the weather can be detrimental to trees if there are open wounds – whether that be down swings or upswings in temperatures. This is most critical when trees are coming out of dormancy in the late winter/early spring.
Branch Assessments
- This is a great and simple way to determine your fruit to vegetative bud ratio. This strategy can give you a better idea of where you stand for your target crop load after precision pruning during the winter.
- Gather at least 10 representative branches, with varying years of growth (3rd, 2nd and 1st year) per block in the spring before bud break and place into buckets inside. The buds will then break and allow you to establish a fruit to vegetative bud ratio to better determine pruning and thinning strategies.
Bud Thinning
- This is a time consuming and labour-intensive way to lower your bud counts. That being said, using this method for highly biennial apples or return apples to make the cost of this method worth it.
Hand Thinning
- Although highly utilized, this common method of thinning should only be used as a last resort. All of you know the high costs associated with using hand thinning, and therefore methods that can be utilized in advance are suggested. Dr. Terence Robinson from Cornell University suggests that only 5% of your thinning strategy should be reliant on hand thinning (Figure 1).
Hedging
- Hedging can be performed in the winter and/or in the summer. Creating a box can be easier for some growers to better manage future pruning. Although hedging isn’t necessarily precision, it enables you and your employees to see trees more clearly when making decisions regarding pruning, training and thinning.
Tools
Trunk Thinning Gauge
- Utilize this to get an idea of what your target crop load should be per tree, although this may change based on your ideal market and the tree architecture you have in your orchard
- Commonly utilized during fruitlet thinning, but can be used earlier for an estimated target crop load
Equilifruit Disk
- Utilize this to get an idea of what your target crop load should be per branch.
- Commonly utilized when hand thinning, but can be used earlier for an estimated target crop load
Mechanical Thinners
- The Darwin thinner is the only mechanical thinner that I am aware of available in Ontario. Ideally the Darwin would be utilized during king bloom or a little earlier as later use could result in dented fruitlets.
Chemical Thinners
These include bloom and fruitlet thinners
- If you have no experience utilizing chemical thinners and are considering changing/adding a chemical thinner to your thinning toolbox, please do this cautiously. This should be done on a small trial basis until you are more comfortable with the product(s).
- These products can be great for nibble thinning and can significantly reduce the cost of hand thinning. There are various products available – please check out the Crop Protection Hub for more details – and can be utilized from king bloom to fruitlet sizing.
- Timing is different for each product and variety, but ideal timing usually ranges from 7 to 10mm based on king fruitlet sizing. Consider the weather conditions in Table 1 to further aid your application timing.
Weather Conditions | Prediction |
Warm Conditions (>18oC) | All thinners work best |
Dark Cloudy Weather | Greater stress Greater thinning response Greater drop |
High Night Temperatures (>18oC) | Great stress High demand and use of energy for night respiration Greater drop |
Very High Day-Time Temperatures (>29oC) | Great stress High energy demand Greater drop |
Very Cool Temperatures (<18oC) | Reduced stress Reduced energy demand Greater set |
High Light | Increased supply: harder to thin |
Low Light | Reduced supply: easier to thin |
Low Temperatures | Low demand: harder to thin |
High Temperatures | High demand: easy to thin |
Low light and warm temperatures | Worst |
A few final notes about chemical thinning:
- The earlier you start, the more opportunity you have to get to your ideal crop load
- The earlier you start, the less chance of over thinning later on
- Trying a new tool on each variety will vary in its effectiveness
- Start small with each new product
Apps
Ferri App
- This app was developed by Joe & Tom Ferri, which incorporates the fruitlet growth model
- The app allows you to input fruitlet measurements over time after each chemical thinner application and give you an estimation of persisting and abscising fruit
- More information can be found here: http://jmcextman.blogspot.com/2023/01/the-fruit-growth-fg-app.html
Orchard Tools App
- This app was developed by Perennia, which is the first step to determining persisting and abscising fruit
- The app allows you to input fruitlet measurements over time and download an excel file
- You would then transfer the excel file data in the Schwallier & Ferri Excel Sheet for an estimation on chemical thinner efficacy
- To download the app follow this link: https://apps.apple.com/ca/app/perennia-orchard-tools/id1510843988
Podcasts
Listed below are a few episodes related to crop load management and apple thinning. Please keep in mind that some of these episodes are older and information may be specific to the region interviewers or interviewees are from.
Orchard Outlook
This podcast is by Perennia and hosted by Michelle Cortens. The podcast provides tangible, practical advice and information through insightful discussion to help commercial tree fruit growers reach sweet success.
Dr. Tree Fruit and Don
This podcast is by the Penn State Extension team and hosted by Dr. Kari Peter and Don Sefrit. The podcast focuses on providing timely information for tree fruit growers throughout the growing season.
https://extension.psu.edu/drtreefruit
- Fruit Bites 4: 5.18.2022 Thinning Is On Our Minds!
- Season 2 Episode 6: Thinning Advice and an Insect Extravaganza
What’s Killing My Kale?
This podcast is by the University of Minnesota Extension, where extensionists rotate hosting. The Podcast covers research-based solutions to pest issues that affect various fruits and vegetables.
Blogs, Websites & Thinning Guides
OMAFRA Thinning Webpage
https://www.ontario.ca/page/thinning-tree-fruit#section-4
- This page has all the information related to thinning and goes into detail regarding application rates for chemical thinners.
ONFruit Blog
https://onfruit.ca/category/apples/
- This website posts timely information throughout the season, whether it be related insect or disease pressure, growth stages, weather updates and events – we try. Information is posted by various OMAFRA specialists and can be automatically sent to your email once subscribed.
PACMAN (Precision Apple Cropload MANagement)
PACMAN – Precision Apple Cropload MANagement (extension.org)
- This website continues to be updated by various extension specialists across the U.S. as they trial various tools that are coming through the pipeline for apple growers in relation to precision crop load management.
- They have hosted webinars through January, February and March demonstrating various technologies currently available and those to come. Stay tuned for an overview article in the next issue of the Orchard Network Newsletter.
Michigan State University, Thinning Strategies for 2022
- This is a great resource that is annually updated for Michigan growers. Although some of the methodologies aren’t available in Ontario, this is still a great reference for general thinning practices.
Final Notes on Targeting Your Crop Load
The more tools you try, the better your understanding of using a multitude of tools and the more versatile your thinning strategy can be. This makes you more resilient for the variable thinning season to come.
I strongly believe that not every tool is for every grower. Each of you manage your orchard in a way that works for you and your crew – so do your research when trying a new tool or action item and give it time to see whether it would work in your operation. There is always a lower efficiency when trying new things, so be sure to give the strategy a few attempts. If the strategy doesn’t work for, maybe it would work for someone else in the operation that would take on more responsibility to implement it. If it is something that truly doesn’t work for you, it may be one less tool – but you can say that you tried it and maybe in the future you can come back to it.
There are constant advancements in the apple thinning world so keep your eyes peeled (pun intended!) for continuing articles on technologies coming down the pipeline to make your thinning decisions easier. Also stay tuned for apple thinning calendars in relation to the growing season! If you have any questions about thinning your apple crop please reach out to Erika DeBrouwer through text, email, or social media (226-931-4098, erika.debrouwer@ontario.ca, @FruitWiTheSpurs)
