The Q&A Archives: Watermelon diseases

Question: My watermelon plant leaves are covered with a light brown almost skin like appearance, however the vines seem to be growing fine as they spread out from the root, Ive researched a bit and I believe that the fungicide I need to use is chlorothalonil, Is this correct and if not what can I use to eliminate this problem, its a small space along a fence line next to tomato plants in which i water pretty regularly. The watermelon leaves are yellow at a distance like they need water?? There were also squash zucchini and yellow which i had to destroy the zucchini due to a problem with the stems, the yellow is still there however not doing very well. Please help and thank you

Answer: I wish I could go out into your yard and look at your watermelon plant with you because I'm not convinced your plant is diseased. I've come to this conclusion based on your statement that the vines are growing fine. When a plant is diseased it usually slows or even stops growing. I don't know what the brown might be, but the yellowing could indicate a need for fertilizer. The oldest leaves on a watermelon plant can die back without anything being wrong with the plant. It's just that these leaves have served their purpose and the plant is putting its energy into producing new leaves towards the ends of the stems. If you're concerned about the older leaves you can simply cut them off the plant. I think this is a better approach than spraying with a fungicide. First, you may not be dealing with a disease and there's not much point in spraying if you don't need to. Second, removing the suspect leaves will also remove any disease pathogens from the garden. As long as the plant is producing new leaves and the stems are growing longer each day, there's nothing to worry about.

If you haven't already, try feeding your plants with a 5-10-10 fertilizer or side-dressing with some compost to provide nutrients to your plants. I think you'll see a difference in leaf color and in their growth rate.

Best wishes with your garden!

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