Prohexadione calcium controls shoot growth of pear trees under mild winter conditions

Abstract

The aim of this study was to evaluate the effects of prohexadione calcium (ProCa) on vegetative growth and yield of ‘Carrick’, ‘Packham’s Triumph’ and ‘William’s’ pear trees. The trial was performed at the experimental orchards of the Federal University of Pelotas, Capão do Leão, RS, Brazil (31° 52’ 00" S; 52° 21’ 24" W), during the growing seasons of 2011/12 and 2012/13. Treatments were applied to single-tree replications in a randomized complete block design with four replications as follows: Control (unsprayed), ProCa (ProCa - 750 g ha^-1 i.a.). The ProCa was split in four (187.5 g ha^-1 a.i. each) or three timings (250 g ha^-1 a.i. each) applications in the 2011/12 and 2012/13 growing seasons, respectively. The assessed parameters were: one-year-old shoot length, number of nodes per shoot, average internode length per shoot, trunk cross sectional area (TCSA) increment, pruning weight, number of fruit per tree, average fruit weight, yield per tree and return bloom. The application of ProCa at 750 g ha-1 a.i. satisfactorily controlled shoot growth through the reduction of internode length of ‘Carrick’, ‘Packham’s Triumph’ and ‘William’s’ pears. Besides, return bloom was not negatively affected by ProCa. Therefore, this plant growth regulator is a potential management tool to reduce shoot growth and the need for pruning in pear orchards.