Why Are My Watermelons Rotting?

Most people don’t want to grow watermelons because of rot. Another common reason is the small watermelon fruits that usually fall off the plants instead of growing into the giant fruits. There are four main reasons the small fruits fall off.

1. There could be are too many fruits on a plant

Most watermelon varieties can’t carry more than three fruits on each plant. Therefore, if the plant produces more than three fruits, it aborts the youngest fruits to preserve the older and larger ones. So, count how many healthy watermelons are on each the plant before you get discouraged.

2. The plant isn’t healthy enough

An unhealthy plant can’t support as many melons as a healthy one. Therefore,  if the plant looks yellow,  stunted or in any way less than healthy, that could be the reason your baby melons are falling off.

3. The female blossoms weren’t pollinated enough

Fruits that don’t get enough pollen during fertilization eventually get rejected by the plant. Honeybees must visit a single female flower at least six to eight times and fertilized with between 500 and 1000 grains of pollen, distributed over all the lobes of the stigma, before it is considered adequately pollinated.

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4. The fruits have a fungal disease

There are several types of fungi in the soil that affect melons and cause rot:

Blossom End Rot

This rot causes the blossom end of the melon to turn brown and look like it’s collapsing inward. Blossom end rot usually happens when there isn’t enough rainfall. To avoid this rot, mulch the base of the plants to help keep the roots cool and moist. Rather than a usual mulch, try to use black plastic around the base of the plant to also block weeds. Furthermore, water regularly and remove any damaged fruit.

Belly Rot

This rot is caused by a fungus, Rhizoctonia solani Kuhn. It is most common during warm, humid or exceptionally rainy weather. A black or brown spot appears on the fruit where it touches the ground and then spreads to the rest of the fruit. The spot will looks sunken and spreads very quickly. Try to remove the affected melons and improve drainage. Also, try to keep the developing fruit off the ground.

Gummy Stem Blight

This rot also known as black rot, is caused by the fungus Didymella bryoniae. The leaves appear yellow in the early stages and the watermelons  appear sunken, with dark spots as the infection progresses. These are a greasy-green color at the beginning, but turn dark, brownish-black as the spots enlarge. So, check your plants regularly for signs of black rot. Use fungicides to help prevent gummy stem blight.

Bacterial Fruit Blotch

This fungus causes dark, water-soaked blotches of rot on the fruits. The rind has greasy-looking areas with white mold either on the spot or on the fruit’s stem. The fungus can live in the soil for years so avoid panting where you’ve has this problem before. Ensure there’s adequate drainage, especially after heavy rain. There are also fungicides for bacterial fruit blotch. However, you have to follow manufacturer’s instructions carefully.

Rind Necrosis

Some watermelons have dry, light brown spots. This disease doesn’t affect  the flesh of the fruit itself and you can’t rind necrosis. It just makes the fruit look ugly. To avoid it, plant watermelon varieties that are labeled rind necrosis resistant.

How to prevent rot

Next time you plant watermelons, ensure it’s a completely different area from the one you planted in before. Most importantly, only buy only treated seeds to ensure they don’t have diseases. Furthermore, re-evaluate farming practices such as using too much fertilizer or over/under watering the plant. Check the watermelon vines throughout the growing cycle for signs of diseases. If you catch the disease early, you can minimize the damage. And, if some of the vines have diseases, pull them up and destroy them or bury them to prevent the spread of infections.


10 thoughts on “Why Are My Watermelons Rotting?

  1. educative indeed. i am a first time farmer. have just planted watermelon. your advice will be put to very good use. thank you.

    1. Waoooooooooooooooo!
      This is so amazing and very encouraging, I never thought of of growing watermelon due to fear that it can root, now that I have this knowledge about it, I think it’s the right time I switch my mind watermelon.

      My question is that, is it ok planting it in July?

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