Winter Squash Leaf Spots: Causes & How to Fix It

Check these first

• What colour are the spots, and do they have a yellow halo?
• Are there concentric rings or a mosaic pattern?
• Are the spots only on leaves, or also on stems and fruit?

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.

Other possible causes

• Late Blight — Dark green water-soaked lesions appear on the leaves and expand quickly into brown dead ti…
• Gummy Stem Blight — Gray-brown lesions form at stem nodes and the crown, exuding brown gum and splitting lengt…
• Bacterial Spot — Small water-soaked spots appear on the leaves, later turning brown with yellowing around t…
• Cucumber Mosaic Virus — New leaves show a yellow-green mosaic, crinkle, and the whole plant becomes stunted. Fruit…
• Downy Mildew — Pale yellow to yellow-brown angular lesions form on the upper leaf surface with a gray-pur…
• Gray Mold — Water-soaked brown lesions form on flowers, fruit and leaves, densely covered by a fuzzy g…
• Anthracnose — Light brown to dark brown round lesions with sharp margins form on leaves and fruit, sligh…
• Black Spot — On roses, dark brown lesions with radiating edges form on the leaves, which yellow around …
• Ring Rot — The bark of branches and trunk becomes rough and warty, serving as the inoculum source. Fr…
• 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 winter squash leaf spots 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.

Written byYasuGrowing vegetables and fruit in Chiba, Japan, and building Gadenin. Corrections are welcome. 15 years of growing.