THE USE OF MORPHOREGULANTS INSTEAD OF THE SUMMER CUT IN APRICOT TREES

In South Moravia, where the most extensive plantations of apricot trees on the territory of Czechoslovakia have centred, the »Velkopavlovická« apricot variety is mostly grown. This variety produces fairly long shorts which, during the first years following the plantation, must be cut short to prevent breakage due to the early and heavy crops of fruits. The fertile and quality growths on such long shoots left uncut develop but from 4 to 6 buds, situated beneath the competitive buds, while another 4 to 6 buds produce but quite short growths; the remaining portion of the branch staying bare. It is just for this reason that the summer cut proves well, for this technique allows the apricot tree to produce two series of fertile growth over a single growth season, in agreement with the above morphological parallelism. The interval between 10th to 20th June, when the shoots have attained 50 to 80 cm in length, is considered convenient for the summer cut.

In 2-year-old apricot crowns, and still more in those of the third growth season when quite a large size has already been attained, application of the summer-cut technique becomes a time-consuming matter. It was therefore our aim to replace this technique by a more expedient one; preference being given to the spray of growth retardants. The actual reason for their application was to induce retardation in the growth of the new shoot which, after a certain period of stagnation, would resume its growth, while the buds set prior to application of the retarding agents during the first swing of development would produce premature growth.

Workers of the Institute of Fruit Culture, Brno University of Agriculture, branch of the Faculty of Agronomy at Lednice na Morave, have subjected to testing the effects of morphoregulants as exerted on growth and fertility of apricot, peach, and apple trees. In apricot trees the spray of maleic-acid hydrazide has proved highly effective, while that of chlorcholine chloride (CCC) showed but lesser effects.

The spray of either 2 g maleic-acid hydrazide solution or 2 ml CCC per 1 litre water was first applied early in April, prior to apricot blooming, and the treatment was repeated seven times, or nine times if necessary, at one week's intervals except for the time of blooming.