Troubleshooting
Hubbard Squash problems — and how to fix them
Hubbard Squash (Cucurbita maxima 'Hubbard') 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.
Squash vine borer
Larvae tunnel into the base of the main stem, causing sudden wilting. Look for sawdust-like frass at entry holes. C. maxima is highly susceptible. Use row covers until flowering, then remove for pollination. Inject Bacillus thuringiensis into affected stems or surgically remove larvae.
Powdery mildew
A white powdery coating appears on older leaves from mid-summer onward, spreading rapidly in warm, humid conditions. Improve air circulation, water at the base only, and apply a potassium bicarbonate or sulfur spray at first sign of infection.
Squash bug
Adults and nymphs cluster under leaves and at the base of plants, sucking sap and causing leaves to wilt and turn brown. Hand-pick egg masses (bronze clusters on leaf undersides) and adults. Neem oil or insecticidal soap is effective on nymphs.
Prevent hubbard squash problems before they start
Most hubbard squash issues are care-mismatch, not bad luck. Dial in the basics:
Looking for hubbard squash in general rather than its problems? Read the full hubbard squash care guide — light, water, soil and feeding.
Hubbard Squash problems — FAQ
Why is my hubbard squash squash vine borer?
Larvae tunnel into the base of the main stem, causing sudden wilting. Look for sawdust-like frass at entry holes. C. maxima is highly susceptible. Use row covers until flowering, then remove for pollination. Inject Bacillus thuringiensis into affected stems or surgically remove larvae.
Why is my hubbard squash powdery mildew?
A white powdery coating appears on older leaves from mid-summer onward, spreading rapidly in warm, humid conditions. Improve air circulation, water at the base only, and apply a potassium bicarbonate or sulfur spray at first sign of infection.
Why is my hubbard squash squash bug?
Adults and nymphs cluster under leaves and at the base of plants, sucking sap and causing leaves to wilt and turn brown. Hand-pick egg masses (bronze clusters on leaf undersides) and adults. Neem oil or insecticidal soap is effective on nymphs.