Pests That Affect Corn

Corn Earworm

• The corn earworm is the most dreaded pest that affects corn. These green worms infest the ear and damage the kernels. Once they have infested the ear, they cannot be controlled. Sprays cannot reach them when they are protected by the corn husks.

  While they cannot be effectively controlled once they infest plants, they can be prevented. Insecticidal sprays can protect most ears if spray is applied every few days early in the season. Apply spray when silks begin to appear on ears. Repeat once or twice weekly until most of the silks have wilted and turned brown.

Sap Beetles

• Sap beetles feed on damaged ears. They feed on decayed and damaged plant matter. These insects are attracted to the scent of the ears that have been damaged by earworms. They may feed on undamaged ears, but this is not as likely.

  Sap beetles are not easy to control. They are resistant to pesticides, and they breed in large numbers. Even if you kill many of them, more will come. The best way to prevent sap beetle infestation is to control earworms and prevent damage to ears and plants.

Grubs

• Grubs are very fat white worms. They live in the soil and feed on plant roots and stalks. When grubs feed, they can stunt plant growth or kill them entirely. A severe infestation can cause serious damage to a corn field.

  It is simple to prevent grubs. They tend to live primarily in soil that has been fertilized with too much manure or compost. Add fertilizer sparingly.

  Soil insecticides will usually control grubs. Soil insecticides are highly toxic. Use caution when applying them to avoid becoming ill. Follow package directions carefully.

Cutworms

• There are several different varieties of cutworms. They are usually gray or pale green, but some are brown. They do not always cause heavy damage to crops, but there is the potential that they could. Cutworms usually appear in damp fields with inadequate drainage. They like weeds, so weed control is vital to prevent cutworm infestation. Keep fields well drained. Use a product like Sevin to kill existing cutworms.

European Corn Borers

• The European corn borer is a worm that tunnels into the leaves and stalks of corn plants. This can cause stalks to break. If there are multiple pea-sized holes in corn stalks, it is evidence that corn borers have infested the stalks. Identify corn borers by their fat tan-colored bodies and brown or orange heads.

  Insecticide is not always effective, because it cannot reach the worms that have burrowed deep inside the stalks. It may require two or more applications to control corn borer population.

Armyworms

• Armyworms are fat worms that have shiny skin. They are usually brown on top and light tan on the underside. Armyworms usually infest immature corn in mid to late summer. These worms typically feed on leaves, but may also infest ears and cause damage similar to that caused by earworms. Apply insecticide before armyworms infest ears. Spray cannot effectively reach them once they are inside the ears.

Flea Beetles

• Flea beetles are pea-sized shiny black beetles. Identify infestation by looking for scars on the leaves. The damage they cause can lead to bacterial infections. The bacterial damage is often worse than the damage done by the beetles themselves. Plant corn that is wilt-resistant to minimize issues. Control flea beetle population with insecticidal sprays.