Troubleshooting
Acorn Squash problems — and how to fix them
Acorn Squash (Cucurbita pepo 'Acorn') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Powdery mildew
Near-universal in acorn squash, typically appearing mid-to-late season. Apply preventive potassium bicarbonate sprays, choose resistant cultivars such as 'Table Ace', and maintain good plant spacing.
Squash vine borer
Larvae of a clearwing moth bore into vine bases, causing rapid wilting. In susceptible regions (eastern US), use row cover until flower opening, monitor for reddish egg masses on stems, and plant a second succession crop in midsummer to escape peak adult flight.
Fruit cracking or rot
Caused by irregular watering or fruit resting on wet soil. Use consistent irrigation and place a tile or straw pad under developing fruits to keep them off the ground.
Prevent acorn squash problems before they start
Most acorn squash issues are care-mismatch, not bad luck. Dial in the basics:
- Common squash problems — the species this cultivar belongs to
- Common acorn squash problems — our other guide for the same plant
- What's wrong with my plant? — the diagnosis apps compared
- Acorn Squash watering schedule
- Acorn Squash light requirements
- Best soil mix for acorn squash
- Acorn Squash temperature & humidity
- Full acorn squash care guide
Looking for acorn squash in general rather than its problems? Read the full acorn squash care guide — light, water, soil and feeding.
Acorn Squash problems — FAQ
Why is my acorn squash powdery mildew?
Near-universal in acorn squash, typically appearing mid-to-late season. Apply preventive potassium bicarbonate sprays, choose resistant cultivars such as 'Table Ace', and maintain good plant spacing.
Why is my acorn squash squash vine borer?
Larvae of a clearwing moth bore into vine bases, causing rapid wilting. In susceptible regions (eastern US), use row cover until flower opening, monitor for reddish egg masses on stems, and plant a second succession crop in midsummer to escape peak adult flight.
Why is my acorn squash fruit cracking or rot?
Caused by irregular watering or fruit resting on wet soil. Use consistent irrigation and place a tile or straw pad under developing fruits to keep them off the ground.