Plant growth regulators (PGRs) could be the key to productivity and quality orchards in mild climate growing region conditions like Southern Brazil. Two experiments aimed to evaluate the effect of PGRs sprayed in different application protocols on fruit set, yield, and fruit quality parameters. The experiments were conducted during 2016/2017 and 2018/2019 growing seasons on two different orchards at Correia Pinto, Santa Catarina State, Brazil. Treatments that have been used were control and 6 treatments using Retain (R) with varying rates of growth. Experiment 1 (E1) received one treatment with Thidiazuron 2.0 mg L-1 and another with the combination (Stimulate (R) 2 mL L-1 + Hold (R) 2 mL L-1). Experiment 2 (E2) received four more treatments, TDZ 4.0 mg L-1 and the other three combinations of Retain (R) and Promalin (R) 1 mL L-1. Both trials were on 'Gala' apple trees arranged in a randomized block design. On E1 TDZ and Retain (R), the two higher doses got the best results for fruit set, 130% more than control, and fruit number per tree, 98% more fruits than control. TDZ had the biggest yield, 60 mg ha(-1), followed by the two higher doses of Retain (R), 42 mg ha-1. All doses of Retain (R) had a negative influence on unitary fruit weight. On E2, it is important to highlight the better result in productive performance and fruit caliber on applying 20.7 mg L-1 of AVG in the F2, H, and I stages. That protocol with three applications generated 11% more productivity and 6% higher fruit caliber than protocol with two applications. Thus, it is suggested that a higher number of applications with lower doses may bring better results than a smaller number of applications with higher doses.
