Corn Earworm Controls

Corn in garden

Corn earwormCorn earworms are caterpillars that chew into the kernels just inside the husks of ripening ears of corn.

Corn earworms also chew tomato fruits from the blossom end, eat into bean pods, and nibble lettuce. Earworms also attacks okra and squash.

The corn earworm is a white, green, brown, or red caterpillar with spines. It is about 1½ long. The adult is a brown moth.

Control earworms attacking corn by placing 1 to 5 drops of vegetable oil or mineral oil at the base of the silks inside each developing husk. The oil will suffocate the worms.

Use oil on corn only after the silks have begun to turn brown. The silks turn brown after pollination. A single silk will become a single kernel of corn once it is pollinated. When an ear of corn does not fill with kernels it is most often because of poor pollination.

Other ways to control corn earworms:

  • Draw corn husks closed with a rubber band so that earworms can not enter. Do this after the silks emerge.
  • Attract to the garden beneficial insects such a green lacewings and parasitic wasps—braconid, chalcid, ichneumonid, and trichogramma—which attack earworms. Annual flowers such as alyssum and cosmos and perennial flowers such as yarrow and coneflowers all attract beneficials.
  • Plant corn cultivars that have tightly wrapped husks which exclude earworms. Resistant varieties include Aristogold, Calumet, Country Gentleman, Iona, Seneca, Chief, Senecat Scout, Silver Cross Bantam, Staygold, and Victory Golden.
  • Spray or dust your crop with BT or Spinosad. These natural pesticides can be used once earworms have already crawled into ears.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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