See the common diseases in watermelon, and their treatments, that UF/IFAS researchers put in their latest publication.
In our last blog, we shared management considerations for Florida watermelon growers looking to combat common diseases; the information is from UF/IFAS’s “UF AgriGator Spray Program: Watermelon” publication. In this blog, we’ll share the common diseases in watermelon, and their most common treatments. See the information below.
Common Diseases
“Powdery mildew (PM) typically produces white, powder-like signs on the upper and lower surfaces of watermelon leaves. This disease starts as small, faint, yellowish spots on the leaves that spread to neighboring leaf surfaces. Dry conditions facilitate PM spread; however, infection requires the presence of moisture. Symptoms first appear in the lower canopy on older leaves and can quickly spread throughout a field. PM resistance to fungicides in FRAC groups 1 (e.g., Topsin M), 3 (e.g., tebuconazole), 7 (e.g., boscalid), and 11 (e.g., azoxystrobin) has been identified. Fungicide options for PM are Vivando, Quintec, Rally, Switch, Luna Experience, and Torino; however, there are indications of Torino having reduced efficacy against some PM isolates.”
“Downy mildew (DM) is a continual cucurbit problem in the southern Florida peninsula, while its incidence varies from year to year in the northern half of the state. Lesions start out as yellow angular leaf spots that later turn brown to black in color. Leaf curling and water-soaking are often associated with DM. A white-to-grayish fungal growth will appear on the undersides of leaves displaying these lesions when the leaves are wet from heavy dews, rainfall, and high humidity (> 90%). Protectant fungicides (e.g., chlorothalonil and mancozeb) provide excellent control early in the season, but their effectiveness is limited once DM develops. DM has been reported to have resistance to Ridomil, Revus, Forum, and FRAC group 11 fungicides (e.g., Cabrio, Quadris). Once DM is present, some strong fungicide options are Orondis Ultra and Ranman; however, other good early season options are available. These fungicides should be mixed with a protectant fungicide to provide optimal control.”
“Gummy stem blight (GSB)’s primary symptom is dark circular leaf spots at the margins of the leaf surface. When severely infected, complete leaf necrosis and leaf drop are common. If a severe outbreak happens with heavy leaf drop before fruit set, yield losses can be substantial as exposed fruits experience sun-scalding. The GSB pathogen is known to be resistant to multiple fungicides; hence, a carefully planned fungicide rotation program is necessary to reduce fungicide failure. Fungicides in FRAC groups 11 (e.g., Quadris), 1 (e.g., Topsin-M), and 7 (e.g., Endura) have a high risk of failure. The recommended GSB fungicide rotation programs are FRAC group M5 (e.g., chlorothalonil) with group 3 (e.g., tebuconazole) or premixes (e.g., Inspire Super, Luna Experience, Aprovia Top, Miravis Prime).”
“Bacterial diseases: Bacterial fruit blotch (BFB) symptoms appear as dark greasy spots on the fruit and irregular spots on the leaves. The foliar application of FRAC group M1 (copper-based compounds) or group P (Actigard) fungicides can manage the disease. Copper-based compounds should be applied two weeks before female flowers open, at bloom, and two weeks after bloom. This will help in the suppression of BFB and other bacterial diseases, including bacterial leaf spot/angular leaf spot. Actigard should also be applied early in the season and before the start of the infection to be effective. These strategies, coupled with maintaining healthy transplants, will ensure that bacterial diseases are effectively managed early in the season, which is the critical infection period.”
“Fusarium wilt (FW) causes vine wilting and decline. Symptoms are often more pronounced on one side of the plant. Older leaves wilt first during the day and recover at night. Vascular discoloration can be seen when the stem is split. Due to the soilborne nature of FW, few fungicides are effective for control. Prothioconazole (Proline 480 SC) or pydiflumetofen (Miravis Prime) can suppress this disease. Please see fungicide label information for application instructions specific to Fusarium wilt.”
See our last blog in the series, looking at spray schedules for watermelon.
Griffin Fertilizer is committed to helping both growers and ranchers make sound agronomic and economic decisions in order to maximize the health of their grove and pasture. As a full-service custom dry & liquid fertilizer blender and crop protection product distributor, we will continue our mission to further advance Florida agriculture. For questions or concerns about your farm or pasture, contact us and one of our team will be in touch.