Tergitol as a possible thinning agent for peach cv. Redhaven

The effect of different blossom thinners ammonium thiosulfate (ATS) (1%, 2%), Armothin (1.5%), Tergitol-TMN-6 (0.5%, 1%), applied on peach cv. Redhaven at 50–60% full bloom was evaluated in thinning experiments in south-west Slovenia. The photosynthesis inhibitor metamitron (0.05%) applied at 8 mm fruit diameter was evaluated as fruitlet thinner as well. Application of 2% ATS resulted in excessive thinning. The thinning effect of 1% ATS was also too strong in two out of three thinning experiments. The use of 0.05% metamitron did not cause any thinning effect on peach trees and gave similar results as the non-treated control. The effective fruit set reduction and increase of average fruit weight was achieved with 0.5% and 1% Tergitol application. In three-year experiment both Tergitol applications reduced fruit set toward hand thinned level, but the share of fruit from bigger size class was only once enhanced to the level of hand thinned trees. No sign of phytotoxicity was noticed on fruits in all thinner application treatments.