Thermal death kinetics in dry air of Diplodia seriata fungus inoculated in vitro in pruned vine shoots

Abstract

The upsurge in fungal diseases that cause grapevine wood rot in young and adult plants remains a major concern for the wine sector. Since pruned vine shoots act as a reservoir of these fungi, there is a need for sanitization methods that can prevent their spread, avoiding plant reinfection. In this work, the effectiveness of dry heat treatments for the disinfection of pruning waste has been investigated. The thermal death of two inocula of Diplodia seriata fungus, associated to black dead arm disease, was studied in vitro at four different temperatures (40, 50, 60 and 65 °C) for different time periods (20, 40, 60, 90, 120 and 150 min) in a dry air incubator. Obtained data confirmed that inhibition increased as a function of temperature and exposure time. First-order and Weibull models were compared to describe D. seriata fungus survival curve kinetics, with high R 2 values (0.923 and 0.930, respectively) and high significances (p < 0.001). Both models predict that the time required to reach 99 % mortality at 65 °C would be 143 min, slightly higher than the experimentally determined minimum time of 120 min. The thermal death kinetics data reported herein has direct applications in process design and validation studies of other grapevine-pruning-waste sanitization methodologies.