Gradual release of PGRs by dispenser application to control suckers in 'Fuji Suprema' apple trees

The use of growth regulators in controlling the growth of apple trees reduces pruning costs, improves efficiency of pesticide treatments and harvesting of fruits. Apple tree bending of new branches is common practice to increase the number of productive structures and the higher incidence of solar radiation and facilitates other cultural practices. However, the present buds formed at the bending in the branch tends to give rise to water shoots, thus requiring frequent pruning. The aim of this study was to develop a new way of applying growth regulators (PGRs). The experiment was conducted in Vacaria, Brazil, in 'Fuji Suprema'. Naphthaleneacetic acid (NAA) was applied at 500, 1000, 1500, and 2000 ppm Prohexadione-calcium (ProCa) 75, 125, 250 and 500 ppm, Trinexapac-ethyl (Tri-E) 200, 300, 400 and 600 ppm paste form, and untreated control. The growth rate was reduced from 28 to 70% by NAA, 62-90% in ProCa and a 72-95% Tri-E compared with untreated plants. The percentage of bud break was reduced in all treatments ProCa, Tri-E and NAA (500 and 1500 ppm) ranging from 32 to 63. The length of branches was less at all concentrations of Tri-E and ProCa.