EFFECT OF THE ARTIFICIAL RAM ON THE EFFIC IENCY OF DORMANCY BREAK TREATMENT IN APPLE-TREES

The objective of this work was to evaluate the influence of the time b etween the treatment application to the dormancy break and the artific ial rain on the bud burst in young apple (Malus domestica Borkh) trees . The experiment was carried out with potted Gala apple samplings duri ng 1992 and 1993. The treatments included application of the chemicals mineral oil (MO) and hydrogenated cyanamide (HC) for dormancy break, associated or not with an artificial rain of 25 mm applied during 45 m inutes. The artificial rain was applied just after the spray with MO p lus HC, at 0.5, 1, 2, 4, 8, and 24 hours. In both years, the treatment for breaking the dormancy without rain resulted in the highest (60.7% ) effect on bud burst. Among the treatments that received artificial r ain, the lowest bud burst was observed when the rain was applied just after the application of the dormancy break treatment. However, there were no significant differences on bud burst among the treatments expo sed to the artificial rain from 30 minutes after spraying MO plus HC, which indicates that the chemical treatment does not need to be reappl ied under these circumstances.