One of my favorite foods from summer gardens is sweet corn. Sweet corn is fairly easy to grow, but many people encounter the frustration of finding corn earworm damage in their fresh produce.
Corn earworm is one of the most common corn pests in the state of Georgia. These insects can be found in just about every field where corn is planted. In some untreated fields, corn earworms can feed on 90-percent or more of the ears.
Adult corn earworm moths lay eggs on the leaves of small corn plants. The worms hatch out and move into the whorl of the corn plant and begin feeding on foliage. The larvae then cover themselves with a plug layer of frass, or excrement, which protects them from predators and pesticides. These early infested corn plants usually end up with tattered leaves.
Corn planted later in the season is in danger of ear damage. Later generations of corn earworm moths lay their eggs directly on the corn silks. Several eggs will be laid on the silks, but only one will make it to the corn ear. This later season feeding can also expose the corn ears to diseases it normally wouldn't encounter.
Corn earworm damage shows itself as tiny trails of missing kernels and excrement. They also affect tomato plants, where they eat buds, chew holes in the leaves and will even bore into the fruit.
To control corn earworm on your sweet corn, you have both chemical and organic options available. If your garden plot is small enough, you can use the organic method of mineral oil control. Using a dropper, apply five drops of mineral oil to each corn ear tip when the silks begin to turn brown. This usually occurs five to six days after silk emergence. If you apply the mineral oil too early, you can disrupt pollination, so make sure to wait for silk browning. Research also shows that adding Bacillus thuringiensis (B.t.) to the oil will improve earworm control.
For larger plots of sweet corn, the mineral oil method is just too labor intensive.
Conventional insecticides, such as carbaryl, bifenthrin and even the bacteria-derived Spinosad can be used against corn earworms. Apply spray solutions when the corn first begins to silk and repeat every two days until the silks have wilted. Spray should be directed at the corn ears.
Your third control option is to simply do nothing. If your corn earworm infestation is on the light side, you can simply use a knife to cut off the damaged parts of the ear. The rest of the ear will still be fine to eat.
Clark MacAllister is the Dawson County extension agent. For more information, call (706)265-2442.