Will powdery mildew kill my squash?

It rarely kills the plant outright, but it weakens it and reduces yield. Keep it under control to protect your harvest.

Should I remove the spotted leaves?

Yes, remove heavily infected leaves to slow the spread. Dispose of them in the trash, not your compost pile.

Winter Squash: spots, causes and fixes

Check these first

Rub the white spots to see if they wipe off like powder.
Check for air circulation around the base of the plant.
Look for signs of yellowing around the spots.

Likely causes

Powdery mildew
Most likely
How to tell: You will see white, dusty patches appearing on the tops of leaves. Eventually, the leaves may turn yellow and dry out.
What to do: Mix 1 tablespoon of baking soda with 1 gallon of water and a drop of dish soap. Spray the solution on the leaves once a week to manage the spread.
Sunscald
Possible
How to tell: Bleached or light tan spots appear on leaves that were suddenly exposed to intense sun. This usually happens after moving a plant or pruning nearby foliage.
What to do: Provide temporary shade for the plant during the hottest part of the day. Avoid pruning too many leaves at once.

Leaf spots on other plants

Find out what's wrong with your winter squash

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

Powdery mildew is common late in the season and usually does not kill the plant immediately. Worry if the spots cover more than half of the foliage.

Stopping it coming back

Space your plants properly to ensure good airflow and always water at the base to keep the leaves dry.

Winter Squash: spots? Check yours with a photo

Every plant is a little different. Take a photo of your winter squash and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

Get the app · Or check it from a photo now, free

Questions people ask

Will powdery mildew kill my squash?: It rarely kills the plant outright, but it weakens it and reduces yield. Keep it under control to protect your harvest.
Should I remove the spotted leaves?: Yes, remove heavily infected leaves to slow the spread. Dispose of them in the trash, not your compost pile.

Guides to these causes

Powdery Mildew

What are these white spots on my winter squash leaves?

Check these first

Not sure what's wrong with your winter squash?