01Yellowing leaves
| Possible cause | Wisconsin | Colorado State |
|---|---|---|
| Potato leafhopper | University of Wisconsin–Madison Extension says with more feeding, the leaf tips develop a distinctive triangular patch of yellowing or browning known by growers as hopperburn. Source page, read 2026-09-27: Potato Leafhopper | No matching line in the Colorado State pages we checked. |
| Psyllids | No matching line in the Wisconsin pages we checked. | Colorado State University Extension says these insects feed on the sap of potato (and tomato) plants and are linked to a condition growers call psyllid yellows. Source page, read 2026-09-27: Recognizing Common Tomato Pests, Pathogens, and Problems |
02Curled or distorted leaves
| Possible cause | Wisconsin |
|---|---|
| Potato leafhopper | University of Wisconsin–Madison Extension says early feeding causes the leaf veins to look pale and makes the leaves themselves curl. Source page, read 2026-09-27: Potato Leafhopper |
03Insects you can see
| Possible cause | Wisconsin | Colorado State |
|---|---|---|
| Potato leafhopper | University of Wisconsin–Madison Extension says adults are tiny, bright green, wedge-shaped insects, widest near the head and tapering toward the wing tips. Source page, read 2026-09-27: Potato Leafhopper University of Wisconsin–Madison Extension says when disturbed, they jump, take flight, or scoot sideways almost instantly. Source page, read 2026-09-27: Potato Leafhopper | No matching line in the Colorado State pages we checked. |
| Psyllids | No matching line in the Wisconsin pages we checked. | Colorado State University Extension says to help confirm this pest, check the undersides of the leaves for the small nymphs. Source page, read 2026-09-27: Recognizing Common Tomato Pests, Pathogens, and Problems |
04Wilting or dying back
| Possible cause | Clemson | Wisconsin |
|---|---|---|
| Black walnut wilt | Clemson Cooperative Extension says plants can wilt when grown too close to a black walnut tree, a cultural problem tied to the tree's location rather than an infection. Source page, read 2026-09-27: Potato | No matching line in the Wisconsin pages we checked. |
| Potato leafhopper | No matching line in the Clemson pages we checked. | University of Wisconsin–Madison Extension says as damage builds up, yellowing and browning spread inward from the leaf edges until whole leaves die off. Source page, read 2026-09-27: Potato Leafhopper University of Wisconsin–Madison Extension says once numbers get high enough, affected potato plants can die outright, a pattern seen specifically in this crop. Source page, read 2026-09-27: Potato Leafhopper |
05Stems and canes
| Possible cause | Colorado State |
|---|---|
| Psyllids | Colorado State University Extension says affected stems can grow in a distorted, zig-zag pattern. Source page, read 2026-09-27: Recognizing Common Tomato Pests, Pathogens, and Problems |
06Fruit, pods and tubers
| Possible cause | Clemson | Wisconsin |
|---|---|---|
| Sun exposure (green skin) | Clemson Cooperative Extension says tubers exposed to sunlight can turn green, a cultural problem rather than a disease, distinct from hollow heart or black walnut wilt. Source page, read 2026-09-27: Potato | No matching line in the Wisconsin pages we checked. |
| Hollow heart | Clemson Cooperative Extension says hollow heart shows up as a hollow space inside the tuber, linked to alternating wet and dry soil rather than a pest or disease. Source page, read 2026-09-27: Potato | No matching line in the Wisconsin pages we checked. |
| Sprouting in storage | Clemson Cooperative Extension says stored tubers can start to sprout if they are kept somewhere too warm, a storage problem rather than a disease. Source page, read 2026-09-27: Potato | No matching line in the Wisconsin pages we checked. |
| Potato scab | No matching line in the Clemson pages we checked. | University of Wisconsin–Madison Extension says look for raised or sunken, corky-textured patches across the tuber surface, the telltale sign of this disease. Source page, read 2026-09-27: Potato Scab University of Wisconsin–Madison Extension says in more severe cases, those corky patches can deepen into large pits on the tuber. Source page, read 2026-09-27: Potato Scab |
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.
Pages compared on this chart
- 2026-09-27 · Potato, Clemson Cooperative Extension
- 2026-09-27 · Potato Leafhopper, University of Wisconsin–Madison Extension
- 2026-09-27 · Potato Scab, University of Wisconsin–Madison Extension
- 2026-09-27 · Recognizing Common Tomato Pests, Pathogens, and Problems, Colorado State University Extension