Prediction of fruit drop of 'Bartlett' pear by a fruit growth rate model

M. Curetti, A.B. Rodríguez, D. Del Brio, P.D. Reeb
A method for early prediction of fruit drop would be a valuable tool to predict initial fruit set and to make thinning decisions. One of the first indicators of fruit abscission is a reduction in the fruit growth rate. In this paper a model for predicting fruit drop was adapted for 'Bartlett' pears from a model that had been previously developed for apples. This model suggests that a fruit will abscise if its growth rate is less than 50% of the growth rate of the fastest growing fruits at a given period of time. A trial was carried out in a 'Bartlett' pear orchard in Rio Negro, Argentina, during two seasons (2009-2010, 2017-2018). Between 360 and 480 fruit clusters were randomly selected and their main fruit were marked for this study. Growth rate of fruits was measured from 22 to 30 days after full bloom until their abscission or harvest. The model was evaluated using the fruit growth rates obtained between the first two measurements. During the trial, about 30-40% of fruits abscised. In both seasons the highest number of abscised fruits was registered during November (more than 85% of total abscised fruits) in concordance with “June drop”. Fruits with initial growth rate lower than 40%, showed more than 75% of abscission. Similarly, as it was observed during the “June drop” period, fruits that abscised close to harvest also showed decreased growth rates in the previous weeks. In conclusion, pear fruits similarly to apple fruits, decelerate their growth rate during the weeks before abscission. This physiological phenomenon could be used for the prediction of fruit drop in 'Bartlett' pears.
Curetti, M., Rodríguez, A.B., Del Brio, D. and Reeb, P.D. (2021). Prediction of fruit drop of 'Bartlett' pear by a fruit growth rate model. Acta Hortic. 1303, 279-284
DOI: 10.17660/ActaHortic.2021.1303.39
Pyrus communis, 'Williams', fruit set, fruit abscission, abscission moment, 'June drop'

Acta Horticulturae