Corn: Pests and Diseases
Earworms
Description
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.
Solutions
- 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.
Cutworms
Description
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.
Solutions
- 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 Bt
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.
Aphids
Description
Tiny
(less than 1/10 inch) soft bodied pear shaped insects
with whiplike antennae. Varied in color. Leaves turn
yellow.
Solutions
Plant
alliums such as garlic and chives. Anise, coriander, nasturtiums,
and petunias may be helpful. Use yellow
sticky traps
or yellow dishes containing
soapy water. Soap-Shield
and mint tea spray is highly effective. Lacewings
will eat 100 aphids
per day.
Birds
Description
Some
birds are nice to have around the garden because they
eat insect pests. Others, such as crows and blackbirds,
can be destructive.
Solutions
Use netting over the
corn row. When harvest approaches, use net bags over
corn ears. Orange and onion bags will do nicely.
