Efficacy of Peroxyacetic Acid for Controlling Gray Mold (Botrytis cinerea) in Stored Table Grapes in California

Postharvest fruit rot diseases limit the storability of table grapes and can cause significant economic losses if left uncontrolled. Gray mold, caused by Botrytis cinerea, is a major postharvest disease of table grapes. This study evaluated the effectiveness of peroxyacetic acid (PAA) in controlling gray mold and other fruit rots and its effects on fruit quality on two grape cultivars. Four concentrations of PAA, 50, 100, 500, and 1000 µg mL-1 applied either by dipping or spraying were tested on grape berries that were inoculated with B. cinerea prior to the treatment. High concentrations (500 and 1000 µg mL-1) of PAA significantly reduced disease incidence and disease severity, regardless of application method or storage temperature, while low concentrations (50 and 100 µg mL-1) showed limited efficacy. The efficacy of three concentrations (100, 500, and 1000 µg mL-1) of PAA were also evaluated for controlling naturally occurring fruit rots in commercially harvested grapes. PAA treatments at 500 and 1000 µg mL-1 significantly reduced the number of decayed grapes during storage compared to the nontreated control, and remained effective after four weeks of cold storage followed by additional two days at 20 °C. In contrast, 100 µg mL-1 PAA was consistently less effective. No negative effects of PAA were observed on fruit quality parameters, such as rachis appearance, berry firmness, soluble solids, and titratable acidity. These results suggest that PAA can be a promising postharvest treatment for controlling fruit rots in stored table grapes.