2019 ASHS Annual Conference

Fusarium wilt of watermelon, caused by the fungal pathogen Fusarium oxysporum f. sp. niveum (FON), is responsible for significant yield loss in watermelon production in Georgia. The disease is also well established in nearly all watermelon growing regions in the United States and the world. In Georgia, the disease causes increasing damage in watermelon production in recent years. Management of Fusarium wilt of watermelon is challenging due to long-term survival of the pathogen in the soil, lack of resistant watermelon cultivars to aggressive races of the pathogen, and limited availability of effective fungicides. In this study, chemical fungicides, biological control agents, and systemic acquired resistance (SAR) inducers were evaluated to develop integrated programs for managing this disease. A number of chemical fungicides and different application methods were evaluated in repeated field experiments in Tifton, Georgia, USA. Two applications of pydiflumetofen through drip irrigation tubes, or drip application of pydiflumetofen at transplanting followed by directed spray of the fungicide two weeks after transplanting, were among the most effective in disease reduction. Directed spray of pydiflumetofen prior to transplanting targeting the area in the field plot for transplanting also reduced disease significantly compared to the nontreated control. Biological control agents, including species of Bacillus and Pseudomonas, were evaluated. The biocontrol agents showed a tendency to enhance disease reduction when applied in conjunction with pydiflumetofen or prothioconazole. Integrated applications of pydiflumetofen with the SAR inducer acibenzolar-S-methyl or prothioconazole consistently reduced disease significantly and were among the most effective treatments. Results of the study provide valuable information and viable options for managing this destructive disease impacting watermelon production.