Zucchini Leaves Turning Brown with Bugs? Likely Vine Borers—Act Fast

Zucchini leaves browning, bugs eating chlorophyll? Probably squash vine borer larvae inside stems—they kill from within.

Diagnose

• Check stem base for frass (sawdust-like excrement) or entry holes
• Slice stem lengthwise—look for white caterpillars with brown heads
• If inside: plant likely doomed
• If on leaves only: still treatable

Organic Control: Diatomaceous Earth (DE)

DE's microscopic shards cut soft bodies. Apply:

• Dust leaves, stems, soil surface
• Reapply after rain/irrigation
• Preventive: mix into planting hole

If Borers Are Inside

• Slit stem, remove larvae, mound soil over wound to encourage re-rooting
• Inject Bt (Bacillus thuringiensis) with syringe
• Yellow sticky traps for adult moths
• Row covers until flowering (remove for pollination)

Succession Planting

Start new seeds every 2–3 weeks in borer-free soil with DE. Late crops often escape peak moth flight.

Vine borers are the #1 zucchini killer. DE at planting + vigilance = survival.