01Yellowing leaves
| Possible cause | Clemson |
|---|---|
| Powdery mildew (many plants) | Clemson Cooperative Extension says when infections get severe, leaves eventually turn yellow, or dry out and turn brown. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants |
| Powdery mildew (vegetables) | Clemson Cooperative Extension says on pumpkin, an advanced infection brings leaf distortion along with yellowing and browning of the foliage. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants |
| Powdery mildew (trees and shrubs) | Clemson Cooperative Extension says on dogwood in particular, leaves can take on a yellow or reddish tint in summer, or develop reddish blotches and dead, scorched-looking patches. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants |
02Spots on leaves
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Powdery mildew (many plants) | Clemson Cooperative Extension says it often starts as small, round, powdery white spots that expand and merge together as the infection spreads. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants | Colorado State University Extension says tiny, pinhead-sized round structures can also appear, starting white and eventually turning yellow-brown then black, either alone or clustered together. Source page, read 2026-09-27: Powdery Mildews |
03Curled or distorted leaves
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Powdery mildew (many plants) | Clemson Cooperative Extension says leaf curling, twisting or off-color patches can show up before the white powdery growth is even noticeable, so the coating isn't always the first sign. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants | Colorado State University Extension says leaves can become distorted and drop earlier than normal, sometimes turning yellow while keeping small patches of green. Source page, read 2026-09-27: Powdery Mildews |
04White or powdery coating
| Possible cause | Clemson | Colorado State | Wisconsin |
|---|---|---|---|
| Powdery mildew (many plants) | Clemson Cooperative Extension says across its many hosts, the shared giveaway is a grayish-white, powdery mat on the surface of leaves, stems and flower petals. Source page, read 2026-09-27: Powdery Mildew on Landscape and Garden Plants | Colorado State University Extension says it's described as patches of white to grayish growth with a talcum-powder look, spreading over the plant surface. Source page, read 2026-09-27: Powdery Mildews | No matching line in the Wisconsin pages we checked. |
| Powdery mildew (vegetables) | No matching line in the Clemson pages we checked. | No matching line in the Colorado State pages we checked. | University of Wisconsin–Madison Extension says on vegetable crops, both leaf surfaces and the stems take on a white, powdery look. Source page, read 2026-09-27: Powdery Mildew – Vegetables |
| Powdery mildew (trees and shrubs) | No matching line in the Clemson pages we checked. | No matching line in the Colorado State pages we checked. | University of Wisconsin–Madison Extension says on woody plants, the white, powdery look covers both sides of the leaves and the stems. Source page, read 2026-09-27: Powdery Mildew – Trees and Shrubs |
05Wilting or dying back
| Possible cause | Wisconsin |
|---|---|
| Powdery mildew (vegetables) | University of Wisconsin–Madison Extension says on crops like cucumber, squash and pumpkin, this disease can cause serious leaf loss on the plant. Source page, read 2026-09-27: Powdery Mildew – Vegetables |
06Stems and canes
| Possible cause | Wisconsin |
|---|---|
| Powdery mildew (trees and shrubs) | University of Wisconsin–Madison Extension says on some shrubs such as rose and ninebark, this disease can cause heavy leaf loss along with dieback at the branch tips. Source page, read 2026-09-27: Powdery Mildew – Trees and Shrubs |
07Fruit, pods and tubers
| Possible cause | Colorado State |
|---|---|
| Powdery mildew (many plants) | Colorado State University Extension says besides the leaf surface, it can spread to the undersides of leaves, young stems, buds, flowers, and even young, developing fruit. Source page, read 2026-09-27: Powdery Mildews |
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 · Powdery Mildew on Landscape and Garden Plants, Clemson Cooperative Extension
- 2026-09-27 · Powdery Mildews, Colorado State University Extension
- 2026-09-27 · Powdery Mildew – Vegetables, University of Wisconsin–Madison Extension
- 2026-09-27 · Powdery Mildew – Trees and Shrubs, University of Wisconsin–Madison Extension