Help solve the problem.
Yellow circles appeared on the leaves of the pumpkin. Proper care, nearby on plants there are no such signs.
Tell me how to solve the problem and how to prevent re-occurrence.
Judging by the photo, the pumpkin is struck by a yellow mosaic (it is often confused with cucumber mosaic), the initial stage. Most likely, you noticed its first signs in the seedling stage: wrinkled leaves, chlorosis. If you do not conduct timely treatment, then the leaves will begin to bend inward, which will affect the growth of pumpkins. Yellow mosaic greatly reduces the immunity of the plant, this leads to additional diseases. The disease spreads rapidly, it should act promptly.
Remove all affected leaves, destroy them. Lightly loosen the soil around the plantings, water under the root and cover with a layer of mulch. Spray with Pharmaiod-3 during the growing season. To protect healthy plantings, use spraying with mineral oils.