Symptom
Mottled or mosaic leaves
A mosaic of light and dark patches, rather than distinct spots, usually means a virus. Nutrient shortages and weedkiller can look similar, but make a more regular pattern.
Look for regularity. Viruses make irregular mosaics on scattered plants; nutrient shortages make repeating patterns on the same leaves of every plant.
Likely causes
Ordered from the usual answer to the less likely one. Each links to the full problem.
Recorded on Pumpkins
Less likely on Pumpkins
-
Viral disease Common
Tomato mosaic virus
Mottled, sometimes fern-like leaves on tomatoes and peppers. -
Viral disease Common
Bean common mosaic virus
Mosaic, blistered, cupped bean leaves. -
Soil & nutrients Possible
Magnesium deficiency
Regular yellowing between veins on old leaves. -
Damage Less likely
Weedkiller damage
Twisted new growth after spraying nearby.