01Curled or distorted leaves
| Possible cause | Clemson | Colorado State | Wisconsin |
|---|---|---|---|
| Aphid colonies | Clemson Cooperative Extension says feeding by some aphid species injects toxins that can leave the plant tissue distorted and deformed. Source page, read 2026-09-27: Integrated Pest Management (I.P.M.) for Aphids | Colorado State University Extension says some aphids cause the leaves to curl when they infest the emerging new growth. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals | University of Wisconsin–Madison Extension says reduced vigor, stunting, and deformed plant parts are common symptoms of an aphid infestation. Source page, read 2026-09-27: Aphids |
02Sticky leaves or black film
| Possible cause | Clemson | Colorado State | Wisconsin |
|---|---|---|---|
| Aphid colonies | Clemson Cooperative Extension says one sign that aphids are present is honeydew, the sticky substance they excrete, on the plant's surfaces. Source page, read 2026-09-27: Integrated Pest Management (I.P.M.) for Aphids Clemson Cooperative Extension says honeydew looks like a sugary drink was poured on the leaves and left to dry, leaving a sticky look and feel. Source page, read 2026-09-27: Integrated Pest Management (I.P.M.) for Aphids | No matching line in the Colorado State pages we checked. | No matching line in the Wisconsin pages we checked. |
| Honeydew and sooty mold | No matching line in the Clemson pages we checked. | Colorado State University Extension says honeydew is the sugary waste that aphids and some other sap-sucking insects excrete. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals Colorado State University Extension says a grayish sooty mold grows on the honeydew, making the plant look worse. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals | University of Wisconsin–Madison Extension says as they feed on plant sap, aphids excrete a sugary substance called honeydew, which attracts ants and lets sooty mold fungus grow on it. Source page, read 2026-09-27: Aphids University of Wisconsin–Madison Extension says sometimes honeydew or sooty mold is the first sign that points to an aphid outbreak. Source page, read 2026-09-27: Aphids |
03Insects you can see
| Possible cause | Clemson | Colorado State | Wisconsin |
|---|---|---|---|
| Aphid colonies | Clemson Cooperative Extension says aphids are usually found on young, tender growth and on the undersides of leaves. Source page, read 2026-09-27: Integrated Pest Management (I.P.M.) for Aphids | Colorado State University Extension says aphids are small insects found on leaves, stems, and sometimes branches. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals Colorado State University Extension says aphid color varies a lot by species, ranging from very pale yellow to dark, almost black. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals Colorado State University Extension says all aphids are small, from about 1.5 to 5 mm long, with the bigger species found on stems and branches. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals | University of Wisconsin–Madison Extension says aphids are soft-bodied, sap-sucking insects that are sometimes called plant lice. Source page, read 2026-09-27: Aphids University of Wisconsin–Madison Extension says aphids are soft-bodied and pear-shaped, with a pair of tailpipe-like structures, called cornicles, sticking out from the rear of the abdomen. Source page, read 2026-09-27: Aphids |
| Green peach aphid | Clemson Cooperative Extension says the green peach aphid is the most common aphid species found feeding on many kinds of plants in the garden and landscape. Source page, read 2026-09-27: Integrated Pest Management (I.P.M.) for Aphids | No matching line in the Colorado State pages we checked. | No matching line in the Wisconsin pages we checked. |
04Wilting or dying back
| Possible cause | Colorado State |
|---|---|
| Aphid colonies | Colorado State University Extension says when aphid numbers stay very high for a long time, their feeding can cause wilting and sometimes even the dieback of shoots and buds. Source page, read 2026-09-27: Aphids on Shade Trees and Ornamentals |
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 · Integrated Pest Management (I.P.M.) for Aphids, Clemson Cooperative Extension
- 2026-09-27 · Aphids on Shade Trees and Ornamentals, Colorado State University Extension
- 2026-09-27 · Aphids, University of Wisconsin–Madison Extension