Corn earworm is a serious pest in corn, especially sweet corn. Let’s talk about this pest, what damage it does and what can be done to control it.
Corn earworm and tomato fruitworm are really the same species of caterpillar. Its just that when we see them on corn it’s an earworm, and when we see them on tomatoes we call it a fruitworm. These are caterpillars that turn into moths. The moth stage has yellowish-brownish wings with a dark spot in the center. The larval or caterpillar stage vary in color and can be brown, pink, green, yellow, or black. They typically have alternating dark and light lateral lines the length of their body. Corn earworm moths lay eggs on the silks of an ear of corn. In tomatoes they are laid on the leaves. As the eggs hatch the baby caterpillars will move down the silks into the ear of corn. On tomatoes they will move into the fruit. They will begin to eat the corn or tomato. In tomatoes they will carve tunnels through the fruit, while on corn they will eat the kernels on the tip of the ear. Sweet corn is a particular favorite of corn earworms so you should expect to see damage on at least some of your corn if you grow it yourself or buy it at a farmer’s market. In corn there is typically only one caterpillar per ear. The moth stage does not cause any damage.
Corn earworm are very difficult to control. The Georgia Pest Management Handbook states, “For caterpillar pests of ears, if damage free ears are desired, begin treatment when silks appear. Repeat at 2-day intervals with sprays directed at ears. Daily applications may be required in the fall and damage may still occur.” You can download the pdf version of the Georgia Pest Management Handbook Home and Garden Edition for free at this website. https://extension.uga.edu/programs-services/integrated-pest-management/publications/handbooks.html
Spraying at 2-day intervals is a lot of insecticide, and is probably more than what most people are comfortable with. Spraying that frequently may be doable for a garden, but is not possible on a commercial scale. Especially since once silking has occurred the plants are too tall to drive a tractor through the field. The damage caused by corn earworm is usually minimal as they will eat about 1 ½ inches of the top of the ear. If you have corn earworm damage from corn that you grow or buy simply break or cut off the tip of the ear where the damage is, and eat the rest of the ear. If you purchase sweet corn that has some corn earworm damage, this could be taken as an indicator that the grower did not use a lot of insecticides when growing the corn.
Sweet corn that has corn earworm damage is still marketable and consumers shouldn’t view corn earworm damage as the fault of the farmer or a lower quality product. If you have questions about corn earworm contact your County Extension Office or email me at Jacob.Williams@uga.edu.