Accede is a new fruit-thinning product from Valent BioSciences, USA, and is aimed at thinning fruit on apples, and flowers on peaches and nectarines. The active ingredient of Accede, ACC, is produced naturally by these trees, as a precursor of ethylene (the ripening hormone).
Unlike other ethylene-based products, Accede doesn’t cause gummosis in peach or nectarine, and is not as aggressive when thinning apples. However, the naturally occurring precursor is not sufficient to adequately thin enough fruit.
Dr. John Cline of the University Guelph, Simcoe Research Station, is doing extensive trials on Accede for both apple and peach. It is expected, that this product will receive registration for use, in Canada for the 2024 apple growing season, and soon afterward for peaches. There is much to be learned as timing and weather conditions can influence the efficacy of this product under Canadian conditions.
In the USA, Accede is the only labeled thinning product for peaches and nectarines. It is applied between bloom and petal-fall. This product works by causing early senescence to the flowers, thus preventing fertilization and fruit-set, of the unwanted crop.
For apples, Accede is used when the king fruit has an average size of 8-25 mm. However, this product is mainly intended for late thinning treatments (fruit size 15-18 mm). Of course, there is the natural ‘shedding’ of fruit in early June -known as ‘June drop’, and this is the tree’s way of lightening the load, but it may not always be enough to give the desired results for modern-day orchards.
Presently, the product Sevin (carbaryl) is used as a fruit-thinner extensively -and effectively, and has for many years; it is often tank-mixed with NAA (napthalene acetic acid), or 6-BA (benzyl adenine).
In early days -very early days, fruit thinning was unnecessary as the majority of apples were produced for purposes of cider. And winter stores were not complete until there were 3 or 4 barrels of cider in the cellar. Cider-brandy was known as ‘Apple Jack’. Otherwise, apples were eaten fresh on the farm, or used for livestock feed.
As transportation methods improved, and cold storage became available, apples took on much more important role. In the year 1910, apples could travel the 5,000 miles from British Columbia to England, and rival local production. In fact, when entered into competition, B.C. apples often took first place prizes! ...such was the sophistication of Canadian growers, and the shipping industry.
Often, the question was what to grow? While present-day production has plenty of choice, and apart from specialty markets, there are about a dozen or so main varieties on the market. However, ‘back in time’, the Prince nursery catalogue, published in 1845, of New York state, listed 350 varieties -and only the best were mentioned. In the ‘Fruits and Fruit Trees of America’, Charles Downing in 1869 lists 1,856 named varieties! How do you like ‘them apples’?
Peach and nectarine trees usually set more fruit than they can adequately support. Therefore, crop load adjustment through fruit-thinning is a routine practice adopted by fruit growers, so as to obtain a marketable product of desired sizes.
If ever there was a time when ‘many hands make light work’, it would the time of hand-thinning of fruit. However, because hand-thinning is a timely cultural practice, and so very labour intensive, often with a decreasing supply of skilled, dedicated and available workers, fruit thinning-products have become essential for the successful harvest. Accede will soon be added to the Canadian growers list of fruit-thinners. In some orchards, and in some years, the cost of hand-thinning can be as much as 30% of the total production costs!
Fruit-thinning increases fruit size, and prevents the potential for limb breakage. In addition, a heavy crop load will prevent adequate production of fruit buds for the following year’s crop, and the tree will get into a mode of biennial bearing -light year, heavy year.
For apples, if hand-thinning, young fruit are removed about 20 days after petal fall. For peaches and nectarines, excessive fruit is removed around 40-60 days after full bloom, with the idea of leaving one fruit every 15cm (6”) along the limb. In order to get good quality fruit, there must be a balance of foliage-to-fruit, and accordingly, there must be adequate leaf surface to supply sufficient energy to grow and ripen fruit.
Ongoing research at the Simcoe Experimental Station, and directed by Dr. John Cline, is investigating the use of cameras to ‘see’ the number of fruit or blossoms on a tree, and termed ‘computer vision’. The idea being that these images -along with a certain amount of programming, will help determine what amount of fruit needs to be thinned from a tree.
Precision crop load management, is key to balancing the amount of fruit to the size and canopy of a tree. And, therefore, allow for fruit to be ‘grown-to-size’ for the intended markets. If a farmer was aiming for 100 fruit per tree, for example, the computer images are hoped to help give guidance with the amount of thinning agent required to achieve that goal.
From the road, and to the passer-by, newly established high-density orchards make for an impressive sight. Off-road, and ‘down-on-the-farm’, the skill and management required to operate a successful apple crop to its optimum capacity, and high standard of quality, is nothing less than remarkable! Truly -it is an art as much as it is a science.