White Powder on Leaves (Powdery Mildew)
Last reviewed: October 2026
Quick answer
A white, dusty coating on leaves and stems is usually powdery mildew, a fungus. Pick off badly affected leaves and cut humidity with more airflow, and do not rely on fungicide alone. Mealybugs, salt crust and cold water spots can look similar.[5][4]
Causes and how to tell them apart
Powdery mildew[1][2]
How to tell: A white, dusty growth on leaf surfaces, often starting as small circular spots that join up. Garden sources say it looks like baby powder. Leaves may be distorted.
Powdery mildew, dry brown form[3]
How to tell: Not every case looks white. Some show dry, brown, papery leaf spots instead of the white powder.
Mealybugs[4]
How to tell: Look closely. Mealybugs are small oval insects that cover plants in a cottony or waxy material, often along leaf veins or where leaf stalks meet stems.
Cold water spots[3]
How to tell: White or straw-colored spots or patches after watering with cold water or splashing leaves. These are marks on the leaf, not a growth you can wipe off.
Salt buildup[3]
How to tell: White to grey crust on the soil surface or pot rim, not on the leaves. Do not confuse it with the white or yellow mold-like growth of soil fungi.
Gray mold (Botrytis)[4]
How to tell: The growth is grayish or tan with dusty gray spores, mostly on spent flowers and older leaves, not a clean white powder.
What to do, step by step
- Pick off badly infected leaves and throw them away.[5][3]
- Increase airflow and space plants so air moves between them.[5]
- Lower humidity. Water early in the day, give the plant brighter light, and keep it away from cold drafts near windows and doors.[4]
- Do not overwater, and do not let the plant get drought stressed either.[3][1]
- Try fungicide last. At home, cleanup and drier conditions often do the job, and many fungicides are not labeled for houseplants.[5][1]
- If it keeps coming back or covers the whole plant, a severely diseased plant may need to be thrown out.[1]
How to prevent it
Not sure what is wrong? Scan your plant.
Scan your plantIf you grow one of these plants
- African violet is named as a houseplant often hit by powdery mildew.[1] Pet safety: African Violet
- Begonias are named as often affected.[4] Pet safety: Begonia
- Kalanchoe is named as often affected.[4] Pet safety: Kalanchoe
- Grape ivy is named as often affected.[4] Pet safety: Grape Ivy
- Jade plant is named as a houseplant affected by powdery mildew.[1] Pet safety: Jade Plant
Frequently asked questions
Is the white powder on my plant's leaves mold or mildew?
A white, dusty growth on the leaf surface is usually powdery mildew, a fungus. Check for mealybugs, which look cottony, and for salt crust, which sits on the soil or pot rim.[1][4][3]
What causes powdery mildew on houseplants?
It develops fastest in humid conditions. Poor air flow and overwatering make it worse. Spores often come from dead plant material or from outdoor plants.[3]
Will powdery mildew kill my plant?
Usually not. It makes the plant look bad and, in bad cases, can cause leaves to drop, but it usually will not kill the plant.[4]
Related plant problems
Sources
- Iowa State University Extension: Two Common Houseplant Diseases
- University of Minnesota Extension: Powdery mildew in the flower garden
- Clemson HGIC: Houseplant Diseases & Disorders
- UC IPM: Houseplant Problems
- University of Maryland Extension: Powdery Mildew on Indoor Plants
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Sources: the university extension and horticultural society pages listed above. Last reviewed October 2026.