EasyBloom Forum

How is watermelon plant disease prevented and treated?

Hey Alex...I answered your other post about which watermelons would do best in tropical climates and I didn't even see this question. Sorry about that. I am assuming that you either have some type of wilt or the leaves of your watermelon have a fuzzy, grayish-colored growth on them. Both of these problems can be caused by stagnant water (either on the leaves or at the crown of the plant). FYI, the crown of the plant is basically where the stems touches the soil. Fungi require a good amount of moisture for their spores to germinate. If you water your watermelons by just spraying the plant with water from the hose, you may inadvertently allow water to pool on those big watermelon leaves. This can increase the chances that a fungal spores will germinate. Same thing goes for the soil. If the soil doesn't drain well and the it is soggy all the time, this will increase the chances of disease.

So what can you do once your watermelon has a disease? Well, there's not much you would be able to do at this point. I would recommend cleaning up dead leaves around the melons. Dead leaves are breeding grounds for fungi that cause disease in plants. By cleaning up dead leaves, you would decrease the chance that the fungus can sporulate and start another generation of growth.

When I was doing my research in grad school, I did almost all of my work in greenhouses. Every night we would burn sulfur to decrease the outbreak of powdery mildew. (Powdery mildew is a fungus that looks like that fuzzy, grayish-colored stuff growing on leaves of plants. Watermelons are especially susceptible to it). This practice worked fairly well, but it was done in an indoor setting. I don't believe that it would have the same effect in an outdoor setting. Not to mention, it may be difficult to find sulfur to burn anyway.

There are some fungicidal sprays/oils that you can purchase, but it has been my experience that these have limited effect. You may have heard how when you see a mushroom, you can rest assure that 99% of that fungus is underground. That mushroom is just the sexual body of the fungus that is there to release spores. Same goes for the fuzzy stuff you see on the leaves. Those are just the spore forming bodies of the fungus. A majority of the fungus is inside the leaf, so using those sprays may not even reach the heart of the problem.

The above advice was written to address fungal diseases, which is what I assume your watermelons are suffering from. Watermelons are also susceptible to viral diseases. The viral diseases are spread via insects that bite into your watermelon. Beetles and aphids should be removed from the plant if you fear that your watermelon may have viral problems.

I hope this is helpful. Let me know if you have any further questions. Happy Gardening! --Robby