APS Homepage

Poster: Biology & Disease Mgmt: Chemical Control


Fungicide rotation schemes and Melcast for managing Phytophthora fruit rot of watermelon in Southeastern United States
C. KOUSIK (1), D. Egel (2), P. Ji (3), L. Quesada-Ocampo (4) (1) U.S. Department of Agriculture, Agricultural Research Service, U.S. Vegetable Laboratory, U.S.A.; (2) Purdue University, U.S.A.; (3) University of Georgia, U.S.A.; (4) North Carolina State U

Phytophthora fruit rot (Phytophthora capsici) limits watermelon production in most states in the Southeastern US. We identified several effective fungicides (Revus, Presidio, and Zampro) to manage Phytophthora fruit rot in our previous studies. In this study, the effectiveness of fungicide rotations and spray applications based on Melcast for managing Phytophthora fruit rot were conducted in P. capsici infested fields at three locations in southeastern US (NC, SC, GA) in 2014 & 2015. The triploid seedless cv. Wonder was used at all locations with diploid cv. Mickylee as the pollenizer. Five weekly foliar application of fungicides were made at all locations. Significant fruit rot was observed in non-treated check plots in both years at all three locations (Mean=68%). All the fungicide rotation schemes significantly reduced Phytophthora fruit rot compared to non-treated check. Overall the rotation scheme of Zampro (dimethomorph+ametoctradin) alternated with Orondis (oxathiapiprolin) was very effective across three locations. Revus (mandipropamid) alternated with Presidio (fluopicolide) was similarly effective in SC. MELCAST reduced one spray application in SC in 2014 but not in NC or GA, and one spray in GA and SC in 2015 with reduction in fruit rot similar to other rotation schemes. Fungicides in different FRAC groups are currently available for use in rotations schemes to manage Phytophthora fruit rot and Melcast may also be useful for scheduling spray treatments.