Abstract
The objective of this work was to evaluate chemical thinning programs containing mixtures of different plant growth regulators, at low concentrations, applied to 'Fuji Mishima' apple trees at post-blossom, as well as to identify the most effective in reducing fruit set, decreasing the need of manual thinning, and improving fruit quality. Under a black anti-hail net, the apple trees were sprayed with the six following chemical thinning protocols (treatments): benzyladenine (BA) + gibberellin4+7 (GA) at full bloom (FB) and BA + carbaryl (CB) on fruitlets with a 15 mm diameter; BA + GA at FB and naphthaleneacetic acid (NAA) + CB on fruitlets with a 7 mm diameter; BA + GA at FB and BA + CB on fruitlets with a 15 mm diameter; ethephon (ETH) + CB on fruitlets with a 15 mm diameter and metamitron (MM) + ETH on fruitlets with a 20 mm diameter; and MM on fruitlets with a 7 mm diameter and MM on fruitlets with a 20 mm diameter. The treatments were compared with an untreated and a manual thinning control. The black net reduced photosynthetically active radiation in 22%. For 'Fuji Mishima' apples under a black anti-hail net, the chemical thinning program consisting of BA + GA (47 + 47 g a.i. ha-1) at FB, followed by BA + CB (80 + 288 g a.i. ha-1) on fruitlets with a 15 mm diameter, consistently reduces fruit set, requires less manual thinning, and improves fruit weight and size.
Index terms:
Malus domestica
; photosynthetically active radiation; plant growth regulators; semi-vigorous rootstock
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