Scale on Pothos: Brown Bumps That Flake Off, and the Fix

Brown bumps along a pothos vine are easy to dismiss as part of the stem. University of Wisconsin–Madison Extension names scale, with mealybugs, as the most common insect pest of pothos in homes (UW–Madison: Pothos). It describes them as bark-coloured bumps that are sometimes hard to tell from the plant they feed on. Scale is persistent, but a pothos is easy to inspect and easy to restart from cuttings.

How to Tell Scale From the Plant

Scale insects are small, immobile and show no obvious legs. Clemson HGIC gives their size as 1.5–13 mm (1/16–1/2 in) across (HGIC 2252).

Check these signs:

• They flake off. University of Maryland Extension says scales flake off with a fingernail, toothpick, cotton swab or soft toothbrush (UMD: Scale Insects on Indoor Plants). A natural bump on the stem does not.
• Where they sit. Look along stems, at nodes and along leaf veins, especially underneath.
• Sticky leaves or surfaces. UMD says honeydew on foliage, or on surfaces below the plant, is the main sign of soft scale. It can turn black with sooty mould.
• Yellowing and leaf drop. UC IPM lists yellowing, early leaf drop and dieback as damage from heavy infestations (UC IPM: Scales).

Pothos produces brown aerial roots at its nodes. These are part of the plant. See our aerial roots guide if you are unsure.

Soft Scale, Armored Scale and Crawlers

UC IPM separates two groups. Soft scales are rounder, and their surface is their body; they excrete honeydew. Armored scales are flatter, with a removable cover; they do not produce honeydew. No honeydew does not rule scale out.

The key stage is the crawler. UC IPM describes crawlers as tiny, yellow to orange nymphs, the only stage with working legs. Within days they settle, lose their legs and stop moving. Clemson notes that adults resist insecticides because of their waxy covering, while crawlers are susceptible.

What to Do

1. Isolate the plant. UMD advises quarantining infested plants. Crawlers walk to the next leaf or pot.
2. Scrape off adults. Use a fingernail, toothpick or soft toothbrush, as UMD suggests. Work along every vine, including leaf undersides and the base of the stems.
3. Prune heavily infested vines. UC IPM recommends pruning heavily infested parts. Bag the trimmings.
4. Spray for crawlers. UC IPM recommends horticultural oil or insecticidal soap when crawlers are active. Colorado State rates horticultural oils as most effective, with soap working on crawlers (CSU: Managing Houseplant Pests). Use a product labeled for houseplants and follow its directions.
5. Repeat. UMD notes that several treatments are usually needed. Colorado State says coverage needs to continue over two to four months to catch new generations.

Colorado State and UMD also list systemic products for indoor use. Choose one only if its label covers houseplants.

When to Discard

Wisconsin says it is often better to discard an infested pothos and start over with clean plants or cuttings than to rely on pesticides. UMD also advises discarding heavily infested plants. Before you do, look for vine tips with no bumps or stickiness. Root those in a fresh container and inspect them weekly. Our pothos propagation guide covers the method.

Prevent a Return

• Inspect and quarantine new plants. Colorado State recommends isolating new arrivals for at least three weeks.
• Check stems when you water. Scale is easiest to clear when only a few are present.
• Look up for stickiness. Honeydew on the shelf or pot is often the first sign.

White, cottony clusters instead of hard bumps point to mealybugs; see our pothos mealybugs guide. For other pests, see the pest treatment overview or return to the pothos hub.

References

• University of Wisconsin–Madison Extension: Pothos, Epipremnum aureum
• UC IPM: Scales
• University of Maryland Extension: Scale Insects on Indoor Plants
• Clemson HGIC 2252: Common Houseplant Insects & Related Pests
• Colorado State University Extension: Managing Houseplant Pests