IPM Checklist
Corn Earworm in Sweet Corn
The short answer
The worms in the tip of your sweet corn are almost certainly corn earworm (Helicoverpa zea), the same insect known as the tomato fruitworm when it attacks tomatoes.
The moth lays eggs on fresh corn silk as it appears, and the hatching larva follows the silk down into the ear, so damage is usually limited to the first 2 to 3 inches at the tip.
Least-toxic management centers on timing: apply a few drops of mineral oil (optionally mixed with Bacillus thuringiensis) to the silks a few days after silks emerge, and choose tight-husked varieties that resist the worm's entry.
Because damage stays at the tip, many home gardeners simply tolerate it and cut off the damaged end at harvest rather than spraying.
How to tell it's corn earworm
Corn earworm is a common caterpillar pest of many vegetables and is the same species as the tomato fruitworm, so seeing it in both crops is normal.
On corn, the moths lay eggs on fresh silk, and fresh silks are favored over older ones. Usually several eggs are laid on the silk of each ear, but only one worm typically reaches maturity in the ear because of natural enemies and cannibalism among the larvae.
✔ Damage is concentrated at the ear tip; UC IPM notes it is usually limited to the first 2 to 3 inches of the ear, so the rest of the ear is normally fine to eat.
Least-toxic timing and silk treatments
The vulnerable window is right after silks appear. Clemson advises applying mineral oil to the corn silks about five to six days after silk emergence to smother eggs and young larvae in the silk channel.
Mixing a Bacillus thuringiensis (Bt) product with the mineral oil can improve control; Clemson describes a ratio of 1 part liquid Bt to 20 parts oil. UC IPM notes Bt may instead be dusted on silks every few days after silk formation begins.
- 1Watch the silks — Note the day fresh green silks first emerge on each ear; this starts the treatment clock.
- 2Apply to the silk channel — Place a few drops of mineral oil (alone or with Bt) onto the silks just inside the tip of each ear a few days after silks first appear, per UC IPM.
- 3Do not over-apply early — Applying oil too early, before pollination is complete, can interfere with kernel fill, so wait until silks have been present a few days.
Resistant varieties and tolerating tip damage
Variety choice reduces pressure. Clemson recommends selecting tight-husked corn varieties because the tight husk inhibits corn earworm movement into the ear; it lists Country Gentleman, Stay Gold, Victory Golden, Silver Cross Bantam, Golden Security, and Silvergent as showing resistance to damage.
The simplest option is tolerance. Because feeding stays at the tip, UC IPM suggests considering not treating at all and simply cutting off the damaged ends of the ears at harvest.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- UC IPM — Corn Earworm or Tomato Fruitworm (Home & Landscape) — Same species as tomato fruitworm; fresh silks favored for egg-laying; damage usually limited to the first 2 to 3 inches of the ear; a few drops of mineral oil on silks 3 to 5 days after silks first appear may be effective; Bt may be dusted on silks; or cut off damaged ends at harvest.
- Clemson HGIC — Insect Pests of Sweet Corn — Moths lay eggs on fresh corn silk as it appears; apply mineral oil on silks five to six days after silk emergence; mixing Bt with mineral oil (1 part Bt to 20 parts oil) improves control; select tight-husked varieties (Country Gentleman, Stay Gold, Victory Golden, Silver Cross Bantam, Golden Security, Silvergent) that resist damage.