How do I know if my indoor plant has a fungal infection?

Introduction

Fungal infections indoors usually show up as powdery films, spotted lesions, or fuzzy gray growth on damaged tissue. Because symptoms can look similar to mineral residue or bacteria, use the simple checks below to confirm fungus before you treat.

1) Powdery, flour-like film that returns

Powdery mildew looks like dusted flour on leaf surfaces or stems. It wipes off but reappears in days, especially on crowded foliage with weak airflow. Thin-leaved houseplants and tender new growth are frequent targets.

2) Round or blotchy leaf spots with darker rims

Fungal leaf spots often begin as tan/brown circles with a darker margin; some show yellow halos. Spots may enlarge, dry, and coalesce. Contrast with bacterial spots, which look water-soaked or translucent and can ooze.

3) Fuzzy gray growth on wounds or spent blooms

Gray mold (Botrytis) forms a velvety gray fuzz on aging flowers, injured leaves, or crowded stems, thriving in cool, stagnant air. You may see rapid collapse of nearby tissue after pruning or petal drop.

4) Quick confirmation tests

• Wipe test: mineral residue lifts clean and doesn’t return; mildew returns quickly.
• Texture check: fuzzy tufts on dying tissue = likely Botrytis; flat/powdery film = mildew.
• Spread pattern: fungal spots expand with dry, papery centers; bacterial spots look wet or greasy first.

5) First-aid steps (safe indoors)

• Prune worst-affected leaves/flowers into a bag; sanitize shears between cuts.
• Boost airflow, thin dense canopies, and keep leaves dry overnight.
• Water at soil level in the morning; avoid crowding plants.

Conclusion

If symptoms match fungal patterns, act early with pruning and airflow. Most cases clear with cultural fixes; persistent infections respond to labeled mild fungicides used on a weekly cadence.