Incorporation of air temperature into a model that predicts loosening of sweet oranges by the abscission agent CMNP

Bob Ebel, Jackie Burns


CMNP (5-chloro-3-methyl-4-nitro-1H-pyrazole) is an abscission agent that is in the process of being labeled as an aid for mechanical harvesting. A mathematical model that incorporates the most important factors affecting CMNP efficacy may be a useful tool for mechanical harvesting companies and growers to schedule abscission sprays and harvests. Previous research has demonstrated that two of the most important factors include CMNP concentration and temperature. Using data from previous research, we developed a model using concentration and air temperature and applied it to 18 treatments from 5 studies that included 10 treatments for ‘Hamlin’ and 8 treatments for ‘Valencia’. Inputs into the model included CMNP concentration, hourly air temperature from time of application to harvest, and fruit detachment force (FDF) at time of application. The model calculated a predicted FDF at time of harvest, which was compared to actual FDF. The average FDF for the 18 treatments at time of application was 92 N. The average FDF at harvest was 51 N and the average predicted FDF was 58 N. Thus, the difference between actual and predicted FDF was about 13%. However, there was considerable variation among treatments, with the range in difference between actual and predicted FDF from –40 to 57 N. There was no difference between cultivars in predictability of the model. Factors causing this high variation between predicted and actual FDF at harvest will need to be included in the model before it will be commercial viable.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283