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Cutworms
- Several species of cutworms attack corn, but the injury to corn is similar;
that is, plants are cut down at the soil line. Damage in most fields may be
prevented by early seedbed preparation to allow natural control of the worms. An
insecticide application to the row when damage is first noticed will provide
control.
Corn
Flea Beetle - Seedling corn may be killed by feeding damage from the corn
flea beetle. As the name implies, the beetle hops like a flea. The beetle is
small, black, and about 1/16 inch long. It eats holes in the leaves and feeding
may severely weaken the seedling.
Corn
Earworm and Fall Army Worm - Damage to corn whorl or buds may be
caused by the corn earworm and the fall armyworm. Both insects may be
present in the same field. The larvae are similar in appearance, but the
frontal suture (the inverted Y) on the front of the head is more
distinct in fall armyworm. It also has a more greasy and smoother
appearance than corn earworm because of fewer hairs on the body. Corn
can withstand a considerable amount of whorl damage. When infestations
are heavy enough to cause dead-heart or severe stunting of plants, yield
loss may occur. When worms infest young plants, two to three feet in
height, they may kill the center of the plant and on seedlings, death of
the whole plant may occur.
To
determine the infestation level, check corn whorls for worms. Control is
justified when you find three to six worms per plant. Several
insecticides are effective. It is important that the insecticide be
directed down into the whorl of the corn by using a high volume of spray
material. Thus, ground applications of sprays are usually much more
effective than aerially applied sprays.
Chinch
Bugs - Chinch bugs occasionally attack corn and may cause severe
stunting and yield reductions. Chinch bugs are routinely a problem in
certain areas of the state and intensive management may be required to
control this insect. Adult chinch bugs are 1/6 to 1/5 inch long, and
wings on the back are black with white covers crossed with a black
zigzag line. Young immature nymphs have red bodies with a white stripe
across the back. Older nymphs are darker, lacking the stripe and reddish
abdomen. Chinch bugs are normally found near or below the soil line and
behind leaf sheaths.
Grasshoppers
- Grasshoppers may occasionally be a problem in field border rows. The
control of grasshoppers is usually necessary only in localized areas of
the field and spot treatments are usually the best way to apply
controls.
Corn
Leaf Aphid - The corn leaf aphid is occasionally found in large
numbers on corn. The corn leaf aphid is a small, bluish-green aphid. The
aphids may be found in clusters on leaves and down in the whorl. Control
is not normally recommended because infestations rarely cause yield
reductions. Aphids are parasitized by a small wasp species and are also
susceptible to a fungus disease. Brown, swollen aphids, abnormally
larger than other aphids in the colony, indicate parasitism. Several
predators also feed on aphids including lady beetles, syrphid fly
larvae, insidious flower bugs and green lacewing larvae. These and
several other insects prey upon aphids and assist in maintaining
populations in check. Treatment for corn leaf aphids is seldom needed. 
Sugar
Cane Beetle - Sugar cane beetle, also called rough headed corn stalk
beetle, is a black beetle about 1/2 inch long. It burrows into the
ground and feeds on the corn stem about 1/2 to 1 inch below the soil
surface, making a ragged hole in the stem. It is most prevalent in the
low wet spots in a field. Infestations do not occur every year. The
sugar cane beetle is difficult to control, but insecticides listed for
cutworms in help suppress the pest.