Modelling metamitron-induced fruit drop as related to photoinhibition stress, dosage and number of applications in ‘Golden Delicious’

Research was carried out in Emilia-Romagna region in a 'Golden Delicious' orchard to assess the thinning efficacy of metamitron (commercial name Brevis (R)) applied either as a single or double application. The choice to perform one or two applications depends upon several factors such as the blooming abundance, the fruit load and the climatic conditions from bloom/fruit set until the time of the treatment. Several models, based upon either the carbon uptake or the stress induced by the thinning agent, can be used to decide both the dosage and time of application. The thinning trials carried out a few years ago were used in the present research to model fluorescence data in order to assess their potential in predicting the thinning efficacy in single and double applications of Brevis (R). Considerations were raised regarding the predictions about the need for a second application and, eventually, its dosage based on the new models prompted out in the present study.