Evaluation of Acibenzolar-S-Methyl and Silicic Acid for control of Phytophthora Blight Caused by Phytophthora capsiciin Squash

Shouan Zhang, Waldemar Klassen, Xiaodan Mo, Pinsheng Ji, Amanda J Gevens

Abstract


Phytophthora blight caused by Phytophthora capsici Leonian is a destructive disease of squash (Cucurbita pepoL.) in Florida and worldwide. Greenhouse studies were conducted to evaluate the potential of acibenzolar-S-methyl and silicic acid for control of Phytophthora blight in squash. Applied as a soil drench or foliar spray, acibenzolar-S-methyl alone at 20 and 30 mg·L–1 significantly (P< 0.05) reduced disease severity compared to the nontreated control. AcibenzolarS-methyl applied as a soil drench at 30 mg·L–1 provided the greatest protection with no symptoms developed on treated squash plants. Silicic acid applied as a soil drench at 0.015 and 0.15 mM significantly suppressed disease severity by 47.7% and 53.3%, respectively, and increased Si concentration in squash roots by 36.2% and 44.4%, respectively, when compared with the nontreated control. Soil application of silicic acid in combination with acibenzolar-S-methyl improved the efficacy of silicic acid and acibenzolar-S-methyl each applied separately against Phytophthora blight. In vitro testing indicated that neither silicic acid nor acibenzolar-S-methyl at test rates suppressed P. capsiciby inhibiting growth of mycelia, production of sporangia or germination of zoospores. Results in this study suggest that acibenzolar-Smethyl and silicic acid were effective against P. capsiciin squash and may be incorporated into integrated management programs for control of Phytophthora blight in squash.


Keywords


Cucurbita pepo, systemic acquired resistance

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283