Corn: Pests and Diseases

Corn: Pests and Diseases


This ugly caterpillar can grow to 2 inches and comes in shades of green, pale yellow and brown. Adults are dull beige or gray moths with a 1½ inch wingspan and a few black spots. They begin munching the tender shoots as soon as they break ground. They chew tassels and interrupt pollination and kernel development. Inside the ears they will consume kernels and leave globs of fecal material.


  • Fall and spring tilling helps by exposing the pupae to wind, weather, and predators. Early plantings of corn may avoid damage and cold, damp weather discourages earworms almost as much as it does the corn.
  • Corn varieties with tight husks are physically more resistant to earworm damage. Try Country Gentleman or Silver Cross Bantam. Clipping a clothespin on the tip of each ear can help to keep husks tight.
  • Try
  • Wormwood Spray or a spray made from garlic and onion tea.
  • A drop of mineral oil on the tip of each ear may help to suffocate any resident earworms. Give the mineral oil by mixing with pureed African marigolds or geranium leaves. Do not apply mineral oil until pollination is complete.
  • Check you garden supply store to see what insect predators are available.
  • Blacklight traps will destroy earworms, and cosmos, smartweed and sunflowers are good trap crops.

More about Earworms


This is a catchall name for the destructive larvae of hundreds of different species of moths. They are soft, ugly, fat, bristly and of almost any color. Some species climb into plants to feed, but the classic sing of busy cutworms is seedlings gnawed at the base until they fall over. Most damage is done at night.


  • Till soil as early as it can be worked in the spring and allow 2 weeks. This removes weed seedlings that the first wave of larvae depend on for food.
  • Eggs are laid in weeds and grass. Keep the garden clean.
  • Interplant with onion, garlic or tansy to repel cutworms or plant sunflowers as a trap crop.
  • Handpicking is easiest and most productive following a rain or thorough watering and should be done after dark. Cutworms can be spotted with a flashlight.
  • Placing a cardboard collar around young seedlings presents a barrier that cutworms can't cross. Use a piece of a toilet paper or paper towel roll or a paper cup with the bottom torn out.
  • Cutworms love cornmeal, but they can't digest it. The cornmeal can be cut with Bticon for a fatal feast.
  • Molasses mixed with hardwood sawdust is an effective trap when spread around susceptible plants. The cutworms will get stuck in the molasses and can be destroyed in the morning.
  • Adult moths are easily killed with bug zappers.


Tiny (less than 1/10 inch) soft bodied pear shaped insects with whiplike antennae. Varied in color. Leaves turn yellow.

Plant alliums such as garlic and chives. Anise, coriander, nasturtiums, and petunias may be helpful. Use yellow sticky trapsicon or yellow dishes containing soapy water. Soap-Shield and mint tea spray is highly effective. Lacewingsicon will eat 100 aphids per day.


Some birds are nice to have around the garden because they eat insect pests. Others, such as crows and blackbirds, can be destructive.

Use netting over the corn row. When harvest approaches, use net bags over corn ears. Orange and onion bags will do nicely.

More about controlling birds

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