By Kathryn Carter and Erika DeBrouwer, OMAFRA
Background
Undoubtedly 2020 was one of the most challenging years for tree fruit growers in history. Accessing labour was incredibly challenging with Seasonal Agricultural workers showing up later than expected (or not at all) due to challenges with travel restrictions. Growers had to deal with a global pandemic, reduced work crews, and continually changing health and safety regulations.
As a result of the challenges growers faced, it was not a traditional year, and many production practices in the orchard were done as quickly and as efficiently as possible with the labour that was available (which was less than a normal year). As a result, pruning, and thinning may have been reduced and harvest may have been affected leaving unharvested fruit on the trees. What impact can we expect this to have on this years production?
Pruning/Training
Pruning and training fruit trees are important production practices in orchards as they affect tree architecture and size, sunlight infiltration, air circulation, yields, and tree health. For non-bearing trees, training helps develop to develop strong tree architecture that can support crop loads and bring young trees into early production.
With fewer workers for pruning and the introduction of new employees to pruning it is likely that orchards likely need some extra attention this year. Orchards that had reduced yields last year due to frost, will also be more vigourous trees this year, which may require more attention to pruning.
Pruning is very labour intensive task, but it is one the most important production practices impacting fruit quality and yields. This year it will be very important for growers to spend some extra time pruning, and tidying orchards to ensure their long term viability. Before workers arrive, evaluate your orchard and pick out the blocks that might need the most amount of pruning this year. Keep in mind that Rome wasn’t built in one day, and it may take awhile to get orchards back into shape again. Pruning is all about balancing reproductive production and vegetative growth. Excessive pruning will stimulate excessive vegetative growth, creating more work in the long run. In contrast, inadequate pruning can result in reduced fruit bud set, increased disease pressure and poor fruit quality. It is better to make a few well thought out cuts, instead of many cuts which may result in excess vigour and more challenges down the road.
Managing your crop load starts with counting buds while pruning to determine what you want the crop to look like. Precision pruning is a technique that can dramatically change your fruit yield, size and quality when utilized effectively. Based on the goals for your orchard and the crop load that you desire, a generous adjustment is to include 1 to 2 times as many buds as needed.
For apple/ pear growers that have orchards with optimal spacing and structure, mechanical hedging, platforms (for pruning and harvest) can provide opportunities to improve labour efficiency and improve fruit quality in orchards. Keep in mind that the decision to use mechanical hedgers should be made on a block by block basis. Hedging works best on calm and balanced trees. Hedging should be used cautiously as it can stimulate excess vigour if not used at the proper timing, or if used on vigourous trees. While it may be tempting to use mechanical hedging to clean up orchards, it is important to keep in mind that there are pros and cons to mechanization. Stay tuned for an upcoming article on “Fruits of Your Efficient Labour: Mechanization and Automation”.
Plant growth regulators such as Apogee/Kudos are another important tool to managing growth in apple orchards and reducing the need for pruning. Apogee and Kudos (prohexadione calcium) are gibberellin synthesis inhibitors that control vegetative growth. The application of Apogee/Kudos in apple orchards at late bloom to early petal fall (terminal shoots are 2.5 – 7.5 cm) has been shown to result in more open trees, with better light penetration, improved fruit set, and reduced labour requirements for follow up hand pruning. For more information on the use of Apogee in orchards see Plant Growth Regulators (gov.on.ca)
Thinning
Fruit trees tend to be biennial bearing and bear fruit in two-year cycles, consisting of a large crop followed by a small crop. Thinning is the chemical or physical removal of fruit that results in an increase in fruit size, improves fruit quality and reduces biennial bearing tendencies. Growers that had low crops last year (due to spring frosts), may see greater bloom in some orchards this year, resulting in the need for increased thinning. Alternatively, orchards that had heavier crops in 2020 (due to lack of adequate thinning) might expect a smaller crop this year.
For apple and pear growers, chemical thinners will continue to be very important to produce a high quality crop and reduce the amount of follow up hand thinning required. Chemical thinning is a complex process, affected by many variables, making it challenging for growers. Optimizing the timing, number of applications and rates of chemical thinners is important in crop load management. Growers and researchers have been testing several models including the Carbohydrate Model (also known as the MaluSim or Carbon Balance model) and the Fruitlet Growth Model for optimizing chemical thinner applications in apple orchards. The Carbohydrate Model uses weather data (current and forecasted sunlight and temperature) to indicate the sensitivity of the developing apple fruit to chemical thinning. The model is being used in other locations to predict if there is a deficit or surplus of carbohydrate, making the trees either easier or harder to thin. This model is still being evaluated in Ontario, but it has the potential to allow growers to fine tune their rates of chemical thinners. The Fruitlet Growth Model was developed by Dr. Duane Greene, University of Massachusetts, to help predict if fruit will abscise or persist through June drop 7-9 days after thinning application. This information can be used to help determine the impact of the chemical thinner on crop load and determine the need for subsequent thinning applications. The model is based on the assumption that the fruitlets that are not chemically thinned will remain and will grow faster than the abscising fruit. For more information on the fruit growth model see Using the Fruitlet Growth Model in Your Orchard (gov.on.ca).
Peaches and nectarine fruit must be thinned by hand which is very labour intensive and time consuming, but a necessary practice to produce a marketable size fruit. Blossom thinning has not been adopted widely in Ontario orchards due to concerns about the risks associated with frosts, however research has demonstrated that blossom thinning results in larger fruit weight and diameter then hand thinning fruit after bloom. Last year we saw an increase in the use of Darwin string thinners in many peach and nectarine orchards for blossom thinning. Although the open vase system commonly used in peach orchards in Ontario is not optimal for using of these technologies, these systems can help to reduce fruit load especially when used after pruning, which can help to reduce labour costs for hand thinning. Hand string thinners are also available that can be used to reduce fruit.
Harvest Missed
For the growers that did not have enough labour at harvest or reduced the number of picks at harvest and were forced to leave fruit on tree – the greatest challenge this coming year could be in the form of pest and disease management (fruit rots).
The Future
There are many factors affecting this years crop load that are still unknown. How did the dry temperatures last summer impact fruit bud development? How will winter temperatures and spring freezes impact flower buds and yields? As we saw last year in tender fruit orchards, it can be challenging to predict the potential impact of cold temperatures during bloom on crop yields. In some cases last year, we saw much greater frost damage then we anticipated at some tender fruit orchards in Niagara.
Conclusion
Last year’s production practices will have a significant impact on this year’s crop, and it is important to keep that in mind when planning for the upcoming season.
There are many factors affecting this years crop that we still do not know, including the upcoming spring. Although we have a better understanding of potential winter injury and frost risk, we won’t really know the crop load until after June drop.
The tree fruit industry is heavily dependent on labour for pruning, thinning and harvesting fruit. We expect that access to labour will continue to be a challenge through 2021. Although some activities can be mechanized (the use of platforms, leaf thinners, hedging etc.), growers still rely heavily on the use of labour in orchards. As a result, it will be very important for growers to optimize their labour use in 2021.
Stay tuned for an upcoming series of articles titled “Fruits of Your Efficient Labour”, regarding how to become more labour efficient in 2021.
Citations
Precision Crop Load Management – A New Concept (gov.on.ca)
https://rvpadmin.cce.cornell.edu/uploads/doc_739.pdf,
Getting the most out of Apogee | Good Fruit Grower
http://www.omafra.gov.on.ca/english/crops/hort/plantgrowthregulators.htm#apples
Optimizing Tree Performance Using PGRs
Optimizing Fruit-Thinning Strategies in Peach (Prunus persica) Production
Using the Fruitlet Growth Model in Your Orchard (gov.on.ca)
NEWA apple carbohydrate thinning model now improved! | Your NEWA Blog (cornell.edu)
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