Cut replacement chemicals
For over a dozen years, research has been carried out in fruit-growing institutes on replacing cutting with appropriate chemicals, applied to trees in the form of spraying or lubrication. So far, no chemical has been used to replace manual cutting, but ways have been found to reduce it. Chemical preparations used in some countries give the following results:
– limit the growth of young shoots on the branches,
– inhibit the intensity of shoot growth,
– cause the shoot tops to die off, replacing their manual pinching.
After intensive pruning of older trees, vigorously growing shoots called wolves appear at the base of the boughs. These shoots must be cut, because they thicken the crown excessively. The research have shown, that the number of emerging wolves can be reduced by lubricating the cutting wounds with a suitable emulsion containing 1% alphanaphthalenic acid, or salts of this acid (table).
Table. The effect of lubricating wounds after cutting apple trees with emulsion paint and paint with an additive 1% NAA on the number of wolves grown on the tree (according to A. Mica, T. Jacyny and Z. Crazy)
| Apple varieties and their age | Number of wolves on the tree after smearing wounds | |
| paint itself | with paint with additive 1 % THE | |
| Bankroft (13 lat) | 104 | 68 |
| Mclntosh (13 lat) | 74 | 27 |
| Mclntosh (11 lat) | 99 | 53 |
Alphanaphthalene acetic acid is a synthetic growth hormone, used, inter alia, to thin out fruit buds.
In America and Western Europe, a wound care emulsion is sold under the name ,,Three-Hold”. It contains 1% THE. A similar emulsion can be prepared at home by adding R-10 to the white emulsion paint Pomonite liquid, which contains 10% potassium salt of alphanaphthalenic acid. On 1 liter of paint must be added 120 ml Pomonite. To avoid excessive dilution of the paint with Pomonite solution, drain the water from the loose paint before adding this preparation.. After adding Pomonite, the paint must be thoroughly mixed. Fresh wounds should be lubricated, right after cutting. The best results are obtained with trees, that had thick branches cut off. If the cutting was limited to small shoots, for a better result, it is necessary to lubricate not only the wounds but also the bark on the upper side of the branches.
Chemical growth retardants are called retardants. Retardants inhibit the growth of internodes and therefore shoots are shorter, twigs more stocky, compact shape of the crown. Young fruit trees sprayed with retardants create a smaller sum of increments, which makes it possible to limit the cut. Retardants applied to young trees accelerate the formation of flower buds and the entry of trees into the fruiting period.
Two agents, Alar and Ethrel, are used in orchard practice (Ethephon). The active ingredient in Alar is succinic acid dimethylhydrazine. Alar inhibits shoot growth in most species of fruit trees grown in a temperate climate. In order to inhibit the growth of shoots, the Alarem trees are sprayed more or less 4 weeks after flowering. The most commonly used concentration is from 0,1% into 0,2%. For best results, you can spray twice in 4 and 6 weeks after flowering. Subsequent spraying has little effect on tree growth, and more on the quality of the fruit. The fruit of the sprayed trees is smaller, firmer and more colored. Alar can be used to inhibit the growth of wolves by spraying the central parts of the crowns with a lance sprayer at the beginning of June.
Ethrel, like Alar, inhibits shoot growth. The active ingredient in Ethrel is 2-chloroethylphosphonic acid. After the penetration of this preparation into the green parts of the plant, ethylene is released, which is one of the natural regulators of plant growth. Ethrel inhibits shoot growth, accelerates the ripening of the fruit and facilitates their separation from the shoots. On young non-fruiting trees, Ethrel can be used safely by spraying at a concentration of 0,05% (stone trees) into 0,08% (pome trees) in 4 into 6 weeks after flowering. In fruiting trees, Ethrel causes fruit thinning. It can be used in the case of abundant fruiting of trees in order to inhibit the growth of shoots and thin out the buds.
Alar is used more and more often in orchard practice together with Ethrel, and sometimes also with the addition of NAA. Alar in concentration 0,1 % and Ethrel at a concentration 0,05% they are very effective in inhibiting the growth of most apple cultivars (table).
Table. Growth of young Mclntosh apple trees sprayed by 3 next years, 0,1% Alar solution i 0,05% Ethrel solution (according to A. Mica, M. Grochowska and A.. Karaszewska)
| The sum of the increments on trees (m / tree) | ||
| Age of trees after planting into the orchard | sprayed | NO
sprayed |
| 2 year | 5,9 | 9,7 |
| 3 year | 9,2 | 29,0 |
| 4 year | 19,1 | 19,4 |
| Together for 3 lata | 34,2 | 58,1 |
Both Alar and Ethrel preparations are registered in Poland and can be widely used.
Among the means causing shoot apex dieback, acting on the principle of chemical removal, a preparation produced in the USA under the name was found in practical use ,,Off-Shoot-O". It is a mixture of fatty acid esters. This preparation has been used for a long time in Western Europe in the cultivation of azaleas to obtain stocky and compact plants..
In nurseries and orchards, you can spray the preparation "Off-Shoot-O” young apple trees, pears and plums to inhibit the growth of the tops of the shoots and force them to branch. In nurseries, annual maiden trees are sprayed when they are from 60-80 cm in height. In orchards, spraying is performed in the second half of June. The recommended concentration is from 1,5 into 2%. In Poland, this preparation is not yet approved for use. Many other preparations are under research and some of them will certainly find practical application. The three English preparations are the most promising: PP-333, MB-25105 to NC-9634. They act on the tops of shoots, giving similar effects to manual pinching.