Plant Symptom Chart

Disease · 4 symptoms · 3 Extension services

Leaf spots: what the symptom points to

Leaf spots look similar across many plants, but the cause and the fungus or bacteria behind it can be different for each one.

Pick the plant you are growing below and compare how each university extension source describes the spots it sees.

Compared here: University of Wisconsin–Madison Extension, Clemson Cooperative Extension, Colorado State University Extension. Last checked 2026-09-27.

01Yellowing leaves

Possible causeClemson
Cercospora leaf spot (cucurbits)
Clemson Cooperative Extension says around each cercospora leaf spot on cucurbits, the surrounding leaf tissue often turns yellow. Source page, read 2026-09-27: Cucumber, Squash, Melon & Other Cucurbit Diseases

02Spots on leaves

Possible causeWisconsinClemsonColorado State
Septoria leaf spot (tomato)
University of Wisconsin–Madison Extension says on tomato, individual septoria spots do not stay separate for long, enough of them run together on one leaf to destroy most of its tissue. Source page, read 2026-09-27: Septoria Leaf Spot
Clemson Cooperative Extension says septoria leaf spot on tomato tends to begin low on the plant, near the soil, once fruit has started to form. Source page, read 2026-09-27: Tomato Diseases & Disorders
No matching line in the Colorado State pages we checked.
Bacterial spot (tomato)
University of Wisconsin–Madison Extension says bacterial spot lesions on tomato leaves start out yellow-green and get darker, turning brownish-red as they age. Source page, read 2026-09-27: Bacterial Spot of Tomato
Clemson Cooperative Extension says on tomato, bacterial spot lesions can have a yellow ring around them, and the middle of each spot dries out and tends to tear. Source page, read 2026-09-27: Tomato Diseases & Disorders
No matching line in the Colorado State pages we checked.
Early blight (tomato) No matching line in the Wisconsin pages we checked.
Clemson Cooperative Extension says early blight spots on tomato can grow rings inside rings, like a target, once they get bigger. Source page, read 2026-09-27: Tomato Diseases & Disorders
Colorado State University Extension says as early blight lesions on tomato age, tiny pinprick-sized black dots called pycnidia form in the center of each spot. Source page, read 2026-09-27: Tomato Early Blight
Common leaf spot (strawberry)
University of Wisconsin–Madison Extension says common leaf spot on strawberry starts as deep purple-to-red spots on the top side of the leaf. Source page, read 2026-09-27: Common Leaf Spot of Strawberry
No matching line in the Clemson pages we checked.
Colorado State University Extension says on strawberry, leaf spot centers change color over time, starting purple, then fading to tan or gray, and eventually almost white. Source page, read 2026-09-27: Strawberry Diseases
Black spot (rose) No matching line in the Wisconsin pages we checked.
Clemson Cooperative Extension says black spot on rose looks like round, dark blotches on the leaf, eventually rimmed by a ring of yellow tissue. Source page, read 2026-09-27: Rose Diseases
No matching line in the Colorado State pages we checked.
Alternaria leaf spot (cucurbits) No matching line in the Wisconsin pages we checked.
Clemson Cooperative Extension says alternaria leaf spot on cucurbits begins as small, round, tan-colored spots on the leaf surface. Source page, read 2026-09-27: Cucumber, Squash, Melon & Other Cucurbit Diseases
No matching line in the Colorado State pages we checked.
Cercospora leaf spot (cucurbits) No matching line in the Wisconsin pages we checked.
Clemson Cooperative Extension says cercospora leaf spot on cucurbits shows up first on older leaves as circular to irregular spots with a lighter center and a darker edge. Source page, read 2026-09-27: Cucumber, Squash, Melon & Other Cucurbit Diseases
No matching line in the Colorado State pages we checked.
Halo blight (bean) No matching line in the Wisconsin pages we checked.No matching line in the Clemson pages we checked.
Colorado State University Extension says halo blight on beans starts as small, greasy-looking, water-soaked spots on the leaflets. Source page, read 2026-09-27: Bacterial Diseases of Beans
Common bacterial blight (bean) No matching line in the Wisconsin pages we checked.No matching line in the Clemson pages we checked.
Colorado State University Extension says common bacterial blight on beans gives the leaf a scalded look, with water-soaked spots scattered through the tissue. Source page, read 2026-09-27: Bacterial Diseases of Beans
Bacterial brown spot (bean) No matching line in the Wisconsin pages we checked.No matching line in the Clemson pages we checked.
Colorado State University Extension says on beans, mature bacterial brown spot lesions can lose their dead center entirely, leaving what looks like a small shot-hole in the leaf. Source page, read 2026-09-27: Bacterial Diseases of Beans

03Stems and canes

Possible causeClemson
Septoria leaf spot (tomato)
Clemson Cooperative Extension says septoria leaf spot on tomato spreads beyond the leaves onto petioles and stems too, though it leaves the fruit alone. Source page, read 2026-09-27: Tomato Diseases & Disorders

04Fruit, pods and tubers

Possible causeWisconsinClemson
Bacterial spot (tomato)
University of Wisconsin–Madison Extension says on green tomato fruit, bacterial spot lesions are small, raised and blister-like, sometimes ringed with a yellowish halo. Source page, read 2026-09-27: Bacterial Spot of Tomato
No matching line in the Clemson pages we checked.
Early blight (tomato) No matching line in the Wisconsin pages we checked.
Clemson Cooperative Extension says early blight can also reach tomato fruit, where the lesions get large enough to cover almost the whole fruit and still show the same ringed pattern. Source page, read 2026-09-27: Tomato Diseases & Disorders

What to do about it. This site only covers how to recognize a problem. For what to do next, open the Extension page linked in the row: their advice is written for their region and is kept up to date by them.

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