This article discusses the potential use of plant growth regulators (PGR) in sweet cherry production. Labels used for commercial use may vary by product, state and state, and country/region, and packaging recommendations may also vary by packaging shed depending on the target market. Therefore, cherry growers must determine the availability, legality and appropriateness of any potential use in their orchard.
At the WSU Cherry School of Washington State University in 2019, Byron Phillips of Wilbur-Ellis hosted a lecture on plant genetic resources. The reason is very simple. In many ways, the most powerful plant growth regulators are lawn mowers, pruners and chainsaws.
Indeed, most of my cherry research career has been focused on pruning and training, which is the most reliable way to influence the crown structure and leaf-fruit ratio to achieve and maintain the desired tree structure and fruit quality. However, I am happy to use PGR as another tool to fine-tune various orchard management tasks.
One of the main challenges in the effective use of PGR in sweet cherry orchard management is that the response of plants during application (absorption/absorption) and after application (PGR activity) will vary depending on the variety, growth conditions and climatic conditions. Therefore, a package of recommendations is not reliable-as in most aspects of growing fruit, some small-scale experimental trials on the farm may be required to determine the most effective way to deal with a single orchard block.
The main PGR tools to achieve the required canopy structure and regulate canopy maintenance are growth promoters such as gibberellin (GA4 + 7) and cytokinin (6-benzyl adenine or 6-BA), as well as growth inhibition Agents, such as original calcium hexadione (P-Ca)) and paclobutrazol (PP333).
Except for paclobutrazol, the commercial formulation of each drug has the registered trademark of Cherry in the United States, such as Promaline and Perlan (6-BA plus GA4 + 7), MaxCel (6-BA) and Apogee and Kudos (P-Ca) . , Also known as Regalis in some other countries/regions. Although paclobutrazol (Cultar) can be used in certain cherry-producing countries (such as China, Spain, New Zealand and Australia), it is only registered in the United States for turf (Trimmit) and greenhouses (such as Bonzi, Shrink, Paczol) And Piccolo) industry.
The most common use of growth promoters is to induce lateral branching of young trees during canopy development. These can be applied to the leading or scaffolding parts in the paint on the buds, or to individual buds; however, if cool weather is applied, the results may be small.
Alternatively, when the positive long leaves appear and expand, the foliar spray can be applied to the target guide or stent part, or later guided to the extended guide at the point where the syllable side branches need to be formed. Another advantage of spray application is that it usually maintains a higher temperature at the same time to achieve better growth activity.
Prohexadione-Ca inhibits branch and shoot elongation. Depending on the vigor of the plant, it may be necessary to reapply several times during the growing season to achieve the desired level of growth inhibition. The first application can be made 1 to 3 inches from the initial shoot extension, and then reapplied at the first sign of renewed growth.
Therefore, it may be feasible to allow the new growth to reach the required level, and then apply P-Ca to stop further growth, reduce the need for summer pruning, and not affect the growth potential of the next season. Paclobutrazol is a stronger inhibitor and may also inhibit its growth in the next few years, which is one of the reasons why it cannot be used in fruit trees in the United States. The branch that inhibits P-Ca may be more and more interesting for the development and maintenance of training systems. For example, UFO and KGB, they focus on the vertical, branchless leader of the mature canopy structure.
The main PGR tools to improve sweet cherry fruit quality (mainly fruit size) include gibberellin GA3 (such as ProGibb, Falgro) and GA4 (Novagib), alachlor (CPPU, Splendor) and brassinosteroids (homobrassinoids). Ester, HBR). According to reports, the use of GA4 from compact clusters to petal fall, and from flowering to peeling and splitting (starting from straw color, which is reported to reduce the sensitivity to cracking to some extent), CPPU increases the size of the fruit.
Straw-colored GA3 and HBR, regardless of whether they are applied for the second time (usually used for heavier crop loads and reused), may lead to increased size, sugar content and harvest firmness; HBR tends to mature earlier and simultaneously, while GA3 tends to delay and mature simultaneously. The use of GA3 may reduce the red blush on yellow cherries (like “Rainier”).
Applying GA3 2 to 4 weeks after flowering can reduce the formation of flower buds in the following year, thereby changing the ratio of leaf area to fruit, which has a beneficial effect on crop load, fruit setting and fruit quality. Finally, some experimental work has found the application of BA-6, GA4 + 7 in the emergence/expansion of leaves, and the mixed use of the two can increase the expansion and final size of the branches and leaves, thereby increasing the ratio of leaf area to fruit and It is speculated that it has a beneficial effect on fruit quality.
The main PGR tools that may affect orchard productivity involve ethylene: the production of ethylene from ethephon (such as ethephon, Motivate) and the use of aminoethoxyvinylglycine (AVG, such as ReTain) to inhibit ethylene synthesized by natural plants. The use of ethephon in the fall (early September) has shown a certain prospect, which can promote cold adaptation and postpone subsequent spring flowering by three to five days, which may reduce the harm of spring frost. Delayed flowering may also help to synchronize the flowering time of cross-pollinated varieties, otherwise they will not match well, thereby increasing the fruit set rate.
The use of ethephon before harvest can promote fruit ripening, coloring and shedding, but it is usually only used for mechanical harvesting of processing cherries, as they can also promote undesirable fruit softening of fresh market fruits. The application of ethephon may cause bad breath to varying degrees, depending on the temperature or the pressure of the trees at the time of application. Although it is not aesthetically pleasing and will definitely consume resources for the tree, ethylene-induced bad breath usually does not have a long-term negative impact on the health of the tree.
In recent years, the use of AVG during the flowering period has increased to extend the ovule’s ability to accept pollen fertilization, thereby improving fruit setting, especially in low-yield varieties (such as “Regina”, “Teton” and “Benton”). It is usually applied twice at the beginning of blooming (10% to 20% of blooming) and 50% of blooming.
Greg has been our cherry expert since 2014. He is engaged in research to develop and integrate knowledge about new rootstocks, varieties, environmental and developmental physiology, and orchard technologies, and integrate them into optimized, efficient production systems. View all author stories here.