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: Cucumber, Squash, Melon & Other Cucurbit Diseases · checked 2026-09-27

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: Septoria Leaf Spot · checked 2026-09-27
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: Tomato Diseases & Disorders · checked 2026-09-27
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: Bacterial Spot of Tomato · checked 2026-09-27
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: Tomato Diseases & Disorders · checked 2026-09-27
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: Tomato Diseases & Disorders · checked 2026-09-27
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: Tomato Early Blight · checked 2026-09-27
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: Common Leaf Spot of Strawberry · checked 2026-09-27
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: Strawberry Diseases · checked 2026-09-27
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: Rose Diseases · checked 2026-09-27
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: Cucumber, Squash, Melon & Other Cucurbit Diseases · checked 2026-09-27
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: Cucumber, Squash, Melon & Other Cucurbit Diseases · checked 2026-09-27
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: Bacterial Diseases of Beans · checked 2026-09-27
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: Bacterial Diseases of Beans · checked 2026-09-27
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: Bacterial Diseases of Beans · checked 2026-09-27

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: Tomato Diseases & Disorders · checked 2026-09-27

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: Bacterial Spot of Tomato · checked 2026-09-27
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: Tomato Diseases & Disorders · checked 2026-09-27

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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