treatments occur mainly at preemergence. Insect control is very important due to consumer
intolerance at the time of purchase.

Sweet corn is harvested before any kernal denting occurs. Small acreages employ manual labor for
hand picking ears from the plant. Larger commercial acreages use mechanical means to harvest the
ears before maturity so that the kernals remain tender. For processed sweet corn, much of the
harvest is iced to retain high sugar content within the kernals before reaching the processing
facilities.

Over mature crops may be harvested as cattle fodder or used for corn silage.

Black Cutworm

Black cutworm adult moths migrate to southern Illinois from March-May and lay eggs in vegetation in
or around cornfields. The eggs hatch and larvae feed on available vegetation, Earlier instars feed
on corn leaves; later instars cut the plants off near the ground. Fields subject to cutworm
infestation often have preplant infestations of weeds, heavy surface debris, poor drainage, or a
history of cutworm damage. An annual average of 3% of all fields are treated with post harvest
insecticides, and up to 7% of acreage is treated with preplant or preplant-incorporated insecticide
applications. Postemergence rescue treatments are justified when 3% or more of plants are cut and
larvae are still present; preventative treatments are best utilized in no-till systems or where
cutworm damage forces replanting of field.

The most harmful cutworms, including the black cutworm, are those that cut off and feed on young
seedlings. Young cutworm larvae (first through third instars) are very small, and the larvae feed
primarily on corn leaves. This injury is not economic. Older cutworm larvae (fourth and later
instars) cut the plants off at, just below, or just above the soil surface. If the growing point is
destroyed or the plant is cut below the growing point, the plant will not survive. Large numbers of
black cutworms can drastically reduce the plant populations.

Although some growers apply soil insecticides to prevent an infestation of cutworms, this practice
is usually not justified economically throughout most of the Corn Belt. Densities of cutworms are
sporadic and difficult to predict. Consequently, most growers now scout their cornfields, looking
for the presence of cutworms and their injury, and apply a "rescue" or therapeutic insecticide if
the numbers of cutworms found exceed established economic thresholds.

Corn Earworm

The adult earworms are about 1/4 inch long and have a wing span of 1-1.5 inches. Their color ranges
from green, to tan, to dark brown. Females deposit eggs on the foliage, where they hatch within 5-7
days. The egg laying occurs throughout the sweet corn growing season. Larvae cause damage to the
corn by feeding deep inside the whorls, causing holes that measure 1-2 inches across. Proper timing
for applying chemical controls is critical. Begin to treat sweet corn during the silkening stage, at
the start of egg hatch.

Corn Leaf Aphids

Winged corn leaf aphids are blown into Illinois by the prevailing winds. Hot, dry weather is
unfavorable for natural enemies and can lead to severe infestations of aphids, Heavy infestations
will wilt, curl, and cause necrosis of the upper leaves. Aphids excrete honeydew, which coats leaves
and reproductive structures and may interfere with pollination. Certain varieties of corn favor
aphid survival and may have up to 9 generations a year.

Corn Rootworm, Northern and Corn Rootworm, Western

The larvae of corn rootworm beetles cause the most economic damage every year in Illinois. The
larvae overwinter in the soil and undergo three instars while feeding on corn roots, causing lodging
and reducing nutrient and water uptake. It is estimated that of the 11,200,000 acres in Illinois
corn about 200,000 acres are treated annually for corn rootworm.

The corn rootworm complex consists of four species: Mexican corn rootworm (Diabrotica virgifera zeae
Krysan & Smith), northern corn rootworm (D. barberi Smith & Lawrence), southern corn rootworm (D.
undecimpunctata howardi Barber), and western corn rootworm (D. virgifera virgifera). Corn rootworm
larvae chew on and tunnel inside or along the roots during the summer months. As they feed, the
larvae prune roots back to the stalk. Extensive feeding weakens the root systems. Injured plants
cannot take up water and nutrients efficiently and are susceptible to lodging. Yield losses are a
result of both root pruning and lodging.

Management of corn rootworms is usually accomplished by crop rotation or the use of soil
insecticides to prevent severe injury to the roots. A corn-soybean rotation usually provides
excellent control of rootworm larvae because the larvae survive only on corn roots, rootworm adults
do not lay many eggs in soybeans, and rootworms complete only one generation each year. A
corn-soybean rotation may fail to control rootworms when volunteer corn plants in a soybean field
attract egg-laying beetles or when rootworms exhibit prolonged diapause, a biological phenomenon
that allows some eggs, primarily those of northern corn rootworms, to remain dormant in the soil for
more than one winter. This trait has become more common in Illinois within the last few years.

Corn planted after corn is susceptible to injury by corn rootworm larvae, depending upon the size of
the rootworm population. Most producers who grow corn after corn in the Corn Belt usually apply a
soil insecticide at planting time to protect the corn roots from larval feeding injury. Most growers
apply granular insecticides in either a seven-inch
European corn borer
First generation corn borer larvae feed on foliage and bore into the stems of whorl-stage plants.
Second-generation larvae tunnel into ears, ear stalks, and stalk which causes breakage, lodging,
stress, and can significantly reduce yield. It has been estimated that at least 10% of cornfields
are infested every year by 3 or more larvae per plant, and that this level of damage causes an
estimated 9 to 16% yield loss annually. Annually, from 2-5% of acres are treated in Illinois for
corn borer. During outbreak years, as many as 1 millions acres have been treated.
Fall Armyworm
Fall Armyworms overwinter in southern states because they cannot overwinter in locations where the
ground freezes. Larvae range in color from light tan to black. They have a distinct inverted Y on
the front of their head capsule. Fall Armyworms reach lengths of 1-11/2 inches.
Flea Beetle
The different species of flea beetles include the potato flea beetle, the threespotted flea beetle,
and the palestriped flea beetle. The potato beetle is a small shiny black beetle. The threespotted
beetle has an orange colored thorax which has three dark spots on it. The palestriped beetle is dark
brown and has two ivory colored stripes running vertically down its wings. All flea beetles have
enlarged hind legs which allow them to jump when disturbed. Flea beetles cause damage to sweet corn
as they feed on the leaves. They leave numerous amounts of small holes behind, which can cause the
sweet corn to die. In order to control the beetles, fields should be kept weed-free, particularly of
field bindweed and mustard, as they are prefered hosts of flea beetles.

Japanese beetle

The japanese beetles are very strong fliers. They are about 5/8 inch long and overwinter as a larva
or grub in soil. In most cases, it's around July when the adults emerge from the soil in great
numbers and feed heavily upon foliage. Soaking rains can also cause damage, as it urges successive
invasions by the beetles. If effective insecticides are not used, or used in time, beetles from afar
will tend to make their way to the fresh vegetables.

Sap Beetle

As an adult, the sap beetle overwinters in soil or debris. The adult sap beetle is usually 1/8 inch
long, and black. The adults feed on ripening pollen and chew tassels. The larvae can cause damage by
eating into the kernels of roasting ears. Remove damaged ears as soon as possible. Control with a
recommended pesticide
Diseases
For sweetcorn, the most frequently cited diseases and pathogens are:
* leaf blights (Stewart's wilt and blight)
* viruses (Maize dwarf mosaic)
In Illinois, farmers are utilizing conventional tillage systems that assist in disease and weed
control. Fusarium species of fungi, in particular, increase when residues are present. These fungi
are common root rotters and also invade corn stalks, causing stalk rots. Many leaf blights and rusts
are spread through plant residue.

Corn seeds are treated to avoid infection by disease spores in the air and on the seed coat.
Essentially all hybrid corn seed is treated with a broad-spectrum protectant fungicide that adds
very little additional cost to production. Some foliar spraying may be necessary.