Corn Earworms

Latin name: Helicoverpa zea (photo unavailable at this time)

Size: 1 1/2″ long

Color: Green to brown

Life cycle: The corn earworm moth lays white eggs on the leaves or corn silks, typically during August and September. The larvae later hatch and feed on the silks and the ear; after a time, the larvae drop to the ground to pupate in the soil.

Signs of their activity: You’ll see frass (excrement) from the larvae feeding on the silks or end of the ear of corn. The larvae can be seen in or on the ear.

Typically seen on: Corn, but can also cause damage to tomatoes.

Controls: I haven’t had a problem with corn earworms for decades, but when I did, I used an eyedropper to place a drop or two of mineral oil right where the silks emerge from the ear of corn. I did this as soon as the silks were visible. The mineral oil essentially smothered the eggs and/or hatching larvae and worked great. Monitor your corn frequently as soon as the ears start developing, to make sure no problems are arising. Bt is effective on the larvae.

Natural predators: Parasitic wasps such as Trichogramma attack the eggs while, lacewings, big-eyed bugs, ground beetles, spiders, tachinid flies, damsel bugs, minute pirate bugs eat the larvae. Help these beneficial insects out by avoiding the use of insecticides!

Additional information: Purdue Extension’s photos of corn earworms and moths. University of California’s Integrated Pest Management information on Corn Earworm.

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