01Yellowing leaves
| Possible cause | Clemson | Wisconsin |
|---|---|---|
| Armored scale insects | Clemson Cooperative Extension says feeding armored scales remove plant sap, which can turn the foliage yellow. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina | University of Wisconsin–Madison Extension says armored scales inject toxins while feeding on leaf tissue, which kill cells at the feeding site and cause a yellow or brown halo. Source page, read 2026-09-27: Scale Insects |
| Soft scale insects | No matching line in the Clemson pages we checked. | University of Wisconsin–Madison Extension says a heavy infestation of soft scales can cause yellowed leaves, distorted new growth at the tips, twig dieback, or defoliation. Source page, read 2026-09-27: Scale Insects |
02Sticky leaves or black film
| Possible cause | Colorado State | Wisconsin |
|---|---|---|
| Soft scale insects | Colorado State University Extension says as they feed, soft scale insects give off a lot of sticky honeydew that can coat the leaves and become a real nuisance. Source page, read 2026-09-27: Brown Soft Scale – A Common Insect Pest of Indoor Plants Colorado State University Extension says the honeydew left behind by soft scales can lead to sooty mold, a black fungal growth that grows wherever the honeydew lands. Source page, read 2026-09-27: Brown Soft Scale – A Common Insect Pest of Indoor Plants | University of Wisconsin–Madison Extension says large amounts of honeydew from soft scales can make the plant and everything below it sticky, drawing ants, bees, wasps, and flies. Source page, read 2026-09-27: Scale Insects |
03Insects you can see
| Possible cause | Clemson | Colorado State | Wisconsin |
|---|---|---|---|
| Armored scale insects | Clemson Cooperative Extension says adult armored scale insects are the most noticeable stage on the plant, and they may be white, gray, or brown. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina Clemson Cooperative Extension says armored scale insects are covered by a hard, waxy shell that protects their body. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina Clemson Cooperative Extension says armored scales don't make honeydew the way soft scales do, and the hard covering over the adult often shows concentric rings or overlapping layers. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina Clemson Cooperative Extension says armored scale crawlers are tiny and look like little specks of dust moving around. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina | No matching line in the Colorado State pages we checked. | University of Wisconsin–Madison Extension says armored scales get their name from the hard, waxy covering over their body. Source page, read 2026-09-27: Scale Insects |
| Oystershell scale | No matching line in the Clemson pages we checked. | Colorado State University Extension says mature oystershell scales are about 1/8 inch long, brown or gray, and shaped like an oyster's shell. Source page, read 2026-09-27: Oystershell Scale Colorado State University Extension says newly hatched oystershell scale crawlers are pale yellow, active insects that move around on the bark. Source page, read 2026-09-27: Oystershell Scale | No matching line in the Wisconsin pages we checked. |
| Soft scale insects | No matching line in the Clemson pages we checked. | Colorado State University Extension says soft scale crawlers usually settle down on stems, though they can also colonize leaf surfaces. Source page, read 2026-09-27: Brown Soft Scale – A Common Insect Pest of Indoor Plants | University of Wisconsin–Madison Extension says soft scale insects are round to oval and dome shaped, roughly 1/8 to 1/4 inch long when full grown. Source page, read 2026-09-27: Scale Insects |
04Wilting or dying back
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Armored scale insects | Clemson Cooperative Extension says when the infestation gets severe, armored scales can weaken the plant badly enough to kill a tree or shrub. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina | No matching line in the Colorado State pages we checked. |
| Soft scale insects | No matching line in the Clemson pages we checked. | Colorado State University Extension says a heavy soft scale infestation can make leaves drop early and cause branches to die back. Source page, read 2026-09-27: Brown Soft Scale – A Common Insect Pest of Indoor Plants |
05Stems and canes
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Armored scale insects | Clemson Cooperative Extension says feeding armored scales remove plant sap, which can cause branches to die back. Source page, read 2026-09-27: Armored Scale Insects on Ornamental Plants in South Carolina | No matching line in the Colorado State pages we checked. |
| Oystershell scale | No matching line in the Clemson pages we checked. | Colorado State University Extension says when populations are high, oystershell scale feeding can cause limb dieback, and during heavy outbreaks the plant can die. Source page, read 2026-09-27: Oystershell Scale Colorado State University Extension says areas of bark that oystershell scale damaged before often crack later on. Source page, read 2026-09-27: Oystershell Scale |
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 · Armored Scale Insects on Ornamental Plants in South Carolina, Clemson Cooperative Extension
- 2026-09-27 · Oystershell Scale, Colorado State University Extension
- 2026-09-27 · Brown Soft Scale – A Common Insect Pest of Indoor Plants, Colorado State University Extension
- 2026-09-27 · Scale Insects, University of Wisconsin–Madison Extension