Fruit abscission pattern of ‘Valencia’ orange with canopy shaker system

Abstract

Fruit detachment can occur due to natural causes or be mechanically performed by a combination of mechanical stresses that cause tissue breakage in the plant. Forced abscission should not coincide with natural abscission zones (AZ). Abscission zones are very important in citrus harvesting both in terms of the destination market and of the possible damage caused to the tree or fruit. The objective of this study is to determine the abscission pattern of sweet oranges with a canopy shaker and compare it with other detachment systems. Five plots of Valencia oranges were tested during the 2017 and 2018 harvesting seasons, using a commercial tractor-drawn canopy shaker. The diameter, weight and breakage type were evaluated in the cases of natural fall, snap method, mechanical harvesting with canopy shaker, and pull test. Breakage type AZ-C predominated in natural fall (89.0%) and the snap method (79.5%). Similarly, AZ-A predominated for the canopy shaker (58.8%) and pull test (45.3%). Mechanical action on the fruit produced peel tear by breaking the flavedo, which reached highest frequency in the snap method (7.6%). Peel tear breakage required a mean fruit detachment force value of 99.3 N, higher than the average abscission values for AZ-C (88.7 N) and AZ-A (66.6 N). The fruit that remained on the tree after canopy shaker harvesting showed lower mean values of fruit detachment force (16.3%) than the pre-harvest fruit. The frequency of fruit with calyx with the canopy shaker and snap methods was similar, with a mean value of 36%.