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: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 |
| Powdery mildew (vegetables) | Clemson Cooperative Extension says on pumpkin, an advanced infection brings leaf distortion along with yellowing and browning of the foliage. Source: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 |
| 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: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 |
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: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 | 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: Powdery Mildews · checked 2026-09-27 |
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: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 | Colorado State University Extension says leaves can become distorted and drop earlier than normal, sometimes turning yellow while keeping small patches of green. Source: Powdery Mildews · checked 2026-09-27 |
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: Powdery Mildew on Landscape and Garden Plants · checked 2026-09-27 | 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: Powdery Mildews · checked 2026-09-27 | 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: Powdery Mildew – Vegetables · checked 2026-09-27 |
| 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: Powdery Mildew – Trees and Shrubs · checked 2026-09-27 |
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: Powdery Mildew – Vegetables · checked 2026-09-27 |
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: Powdery Mildew – Trees and Shrubs · checked 2026-09-27 |
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: Powdery Mildews · 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.
Pages compared on this chart
- Powdery Mildew on Landscape and Garden Plants, Clemson Cooperative Extension (checked 2026-09-27)
- Powdery Mildews, Colorado State University Extension (checked 2026-09-27)
- Powdery Mildew – Vegetables, University of Wisconsin–Madison Extension (checked 2026-09-27)
- Powdery Mildew – Trees and Shrubs, University of Wisconsin–Madison Extension (checked 2026-09-27)