Check these first
- Does the yellowing start at the bottom of the plant or at the tips?
- Are the veins still green while the rest of the leaf fades? That points to a nutrient deficiency.
- Look under the leaves for tiny insects or white specks.
Most likely causes
From the pests and diseases recorded for this plant, the ones whose symptoms match, most serious first. Symptoms alone rarely confirm a cause, so use the linked page to check the signs and treatment.
Sunscald
The sun-facing side of the fruit bleaches white to pale yellow, then dries into a sunken leathery patch. Rot organisms enter easily through the damaged tissue.
General description; not specific to this plant.
How to identify and treat: SunscaldZucchini Yellow Mosaic
Strong yellow mottled mosaic appears on the leaves, which become narrow and shredded in shape. Fruit is knobbly and lumpy, twisted and bent.
General description; not specific to this plant.
How to identify and treat: Zucchini Yellow MosaicMelon Yellow Spot Virus
Numerous small yellow spots appear on the leaves and later turn necrotic so the leaf dies. Growth stalls and fruit fails to size up or sweeten.
General description; not specific to this plant.
How to identify and treat: Melon Yellow Spot VirusOther possible causes
- Powdery Mildew — White patches appear scattered on the upper leaf surface at first, then the whole leaf is …
- Downy Mildew — Pale yellow to yellow-brown angular lesions form on the upper leaf surface with a gray-pur…
- Verticillium Wilt — Only one side of the lower leaves yellows and wilts, and the symptom moves up the plant. S…
- Leaf Spot — Small round brown to gray-white lesions appear on the lower leaves, the centers turning gr…
Other symptoms on this plant
What other growers did about it
A page like this one can tell you what watermelon leaves turning yellow is and what to try. What it cannot tell you is what actually happened to someone who had it on the same plant, at the same point in the season, and what they did next.
Gadenin is a free garden journal built around that. You photograph the plant, tag what you are seeing, and the entries line up by date for each plant you grow.
- Tag the problem and the app tells you how many other growers have logged the same thing on the same plant.
- Growers who make their records public can be followed, so you can read what they did and how it turned out.
- Next season your own entries come back at the same point in the year, so you check the plant before it starts.
Free on iPhone. Recording, tagging and reading public records cost nothing.