Effects of Triclopyr (3,5,6-trichloro-2-pyridyloxyactetic acid) applications on fruit quality of ‘SRA63’, ‘SRA85’, ‘SRA88’ and ‘SRA92’ Clementine.

In order to improve the yield and quality of Clementine fruits, many trials of treatment with hormonal compounds were carried out in the last years in the South of Sardinia (Italy). Fruit set increase, fruit thinning control, fruit size increase at harvest, fruit drop reduction during maturation, and fruit quality storage on tree, particularly of the peel, were the main objectives of the research program. Four different cultivars of Clementine were tested in 2006 and 2008: SRA63, SRA85, SRA88, and SRA92; as well as trees on two rootstocks: sour orange and Carrizo citrange. In this paper the effects of triclopyr (3,5,6-trichloro-2-pyridyloxyactetic acid), as an alternative to 2,4-D (dichlorophenoxyacetic acid), have been evaluated to increase fruit size and to the control of the pre-harvest natural drop. Triclopyr treatments were more effective both at controlling fruit drop and protecting the peel of the mature fruit when applied early on fruits showing 18-22 mm of diameter (about middle of July) than treatments made at peel colour break time. This treatment in mid-July, determined the increase in fruit size and sometimes of the total yield per tree. Lower yield was generally observed on trees grafted on sour orange than on trees on Carrizo rootstock.