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POSTERS: Chemical control

Comparison of conventional and organic fungicides, application intervals, and cultivars to manage tomato early blight in Tennessee
Zachariah Hansen - University of Tennessee.

Early blight, caused by Alternaria tomatophila, is a serious disease of tomato and fungicides are often applied on a calendar-based schedule for management. The objective of this study was to evaluate conventional and organic fungicide programs under two application intervals for management of tomato early blight. Three cultivars reported to have varying levels of early blight susceptibility were tested: ‘Mountain Glory’ (susceptible), ‘Defiant PhR’ (intermediate resistance), and ‘Mountain Merit’ (intermediate resistance). The average number of days between fungicide applications were 8 and 17 for standard-timing and half-frequency intervals, respectively. The conventional program rotated Inspire Super, Manzate, and Fontelis. The organic program included Double Nickel mixed with Cueva. Cultivars did not differ regarding disease or yield. Conventional and organic programs reduced the area under disease progress curve (AUDPC) compared to the non-treated control (NTC), and conventional AUDPC was lower than organic. The conventional program resulted in higher yields than the organic program. In the organic program final disease severity was approximately 90% for both the standard-timing and half-frequency interval. In the conventional program the standard-timing interval resulted in lower final disease severity (14%) compared to the half-frequency interval (42%). These results will inform early blight management recommendations for Southeastern tomato producers.