Return Bloom and Yield of ‘Rocha’ Pear Trees are Improved by Ethephon and Paclobutrazol

Flower induction and differentiation are complex phenomenon not fully understood in pear trees. Paclobutrazol (Pbz), Ethephon (Eth), and naphthaleneacetic acid (NAA) exogenous applications could be potential tools to increase return bloom and yield, and to manage the alternate bearing in some pear cultivars. The objective of this research was to evaluate the effect of Eth, Pbz, and NAA on return bloom and yield of ‘Rocha’ pear trees in different climatic conditions of Southern Brazil. The experiments were performed during 2015/2016–2017/2018 growing seasons, in São Joaquim, Santa Catarina State, and during 2015/2016–2016/2017 growing seasons in Antônio Prado, Rio Grande do Sul State. The pear ‘Rocha’ were grafted on quince rootstock ‘BA29’ (experiment 1 and 3) and Pyrus calleryana (experiment 2). Treatments consisted of Eth, Pbz, NAA, and Eth + NAA sprayed at different concentrations and timings. Shoot length, pruning weight, fruit set, number of thinned fruit and total fruit per tree, yield, average fruit weight, flesh firmness, and soluble solids content were assessed. Shoot length decreased, whereas return bloom and yield components increased when using Eth, Pbz, and Eth + NAA in all experiments. However, the positive effect is only in the rate of 10 mg L –1 NAA in experiment 1. Fruit size was reduced in Eth concentrations above 300 mg L –1 , as a direct effect of crop load. Our results show that Eth and Pbz increase return bloom and yield of ‘Rocha’ pear trees being a potential tool to improve flowering in warm winter Regions as Southern Brazil.