How to identify
- Sudden vine wilt while leaves still look green
- Sawdust-like frass at holes in the stem base
- Fat white grub with a brown head inside the stem
Damage: Stem girdling; plant collapse midseason.
Control methods
- Wrap stem bases with foil or use row cover until flowers open.
- Plant a second succession of zucchini later in the season.
- If you catch frass early, slit the stem, remove the larva, and hill moist soil over the wound.
What products to use
We list product types and what to check on the label — not brand rankings, prices, or “we tested” claims. Always follow the label for your crop, and prefer the least disruptive option that works.
Bt or spinosad (prevention sprays on stems)
When: When adult moths are flying — timing matters more than product
Look for: Labeled for vine borer on squash; coat stem bases; follow local extension flight timing