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POSTERS: Integrated pest management

Evaluation of tomato cultivars and OMRI fungicides for late blight.
David Perla - Michigan State University. Mary Hausbeck- Michigan State University

U.S. organic tomato production was valued up to $174 million in 2017. Late blight (LB) (Phytophthora infestans) is a destructive disease causing foliar blighting and fruit rot. Cultivar resistance and OMRI-approved fungicides were tested in growth chamber and field studies and evaluated for LB (0 to 100%); early blight (EB) (0 to 10 scale) and bacterial spot (BS) (0 to 100%) in the field were noted. Twelve untreated cultivars were inoculated with P. infestans isolate US-23. In the growth chamber and field, disease incidence was lower in ‘Mountain Magic’, ‘Defiant’, ‘Matt's Wild Cherry’, and ‘Tomato Stellar’ (<40% LB in growth chamber; 0% LB, < 2.5 EB, and < 30% BS in field) compared to ‘Early Girl’, ‘Better Boy’, ‘Rugged Boy’, ‘Amish Paste’, ‘Mountain Merit’, ‘Damsel’, ‘Cherry Bomb’, and ‘Mr. Stripey’ (<95% LB in growth chamber; <20% LB, <3.8 EB, < 70% BS in field). In a separate field study, ‘Mountain Merit’, ‘Damsel’, ‘Mr. Stripey’, and ‘Better Boy’ were inoculated as previously described and treated with Kocide 3000-O (copper hydroxide), Zonix (rhamnolipid biosurfactant), Ef-400 (herbal extracts) or not treated (control) every 7 days. Levels of LB, EB, and BS for ‘Better Boy’ sprayed with Zonix were similar to the control. LB, EB, and BS disease for all cultivars was reduced when Kocide 3000-O was applied compared to either Zonix or EF-400. ‘Mountain Merit’ or ‘Mr. Stripey’ treated with Kocide 3000-O had the lowest levels of disease.