Field Corn Insects

From Bugwoodwiki

Arnet, J.D.; Bertrand, P.; Crawford, J.; Ellis, HC; Lambert, W.; McGlohon, N.; Suber, F.; Thompson, S.; Womack, H.; Brown, E.A.; Evans, B.R. Insect and Disease Identification Guide for IPM in the Southeast. The University of Georgia. Cooperative Extension Service Bulletin 849. September 1981. 59p.

Fall Armyworm (Spodoptera frugiperda)

Fall armyworm larvae hatch from eggs which are deposited in a fuzzy mass usually on the underside of corn leaves. The larvae vary in color from tan or green to nearly black, are about 1 1/2 inches long (38 mm), and have several stripes on the sides and/or back which run the length of the body. A white inverted "Y" is usually present on the dark head capsule. Larvae begin feeding on the leaves. They may completely defoliate seedling corn. On larger corn, the larvae move deep down into the whorl to feed. Infested plants develop a ragged whorl. Corn ears may be attacked by large and small larvae. Larvae are not cannibalistic and several larvae may develop in one ear. This can cause almost complete destruction of the ear.

Corn Earworm (Heliothis zea)

Corn earworm larvae are striped and variable in color. They may be yellowish pink, green, brown or nearly black and are about 1 1/2 inches long (38 mm). The head capsule is usually yellowish-orange. They may damage corn by feeding in the whorl or by feeding on the ears. Larvae usually enter the ears by first feeding on the silks and then moving down the silk channel to feed on the tips of the ears. Usually only one larva per ear is found.

European Corn Borer (Ostrinia nubilalis)

European corn borer larvae are flesh-colored caterpillars with inconspicuous small, brown spots and are about 1 inch long (25 mm). Eggs are laid in masses, individual eggs overlapping each other like fish scales. Egg masses are laid on the underside of corn leaves. After hatching, larvae begin feeding on the leaves. They leave shot-hole-like feeding damage in the whorls of corn. They bore within stalks and ears in later stages of corn development. Slimy borings often protrude from small holes where the larvae enter the stalks. Larvae usually enter the ear through the side of the ear. They feed up and down the ear. Heavy infestations are characterized by broken over tassels and stalks caused by larval tunneling in the stem. Ears may also fall from the plant when the weakened ear stem breaks.

Lesser Cornstalk Borer (Elasmopalpus lignosellus)

The lesser cornstalk borer is relatively small, 1/2-3/4 inch (13-18 mm), bluish-green or reddish-brown in color and has dark bands around the body. It will "whip" about rapidly when disturbed. It attaches a soil-covered, silken tube to the plant just below the soil level and from this tube tunnels into the stem. This tunneling kills small seedlings outright. Larger seedlings may survive but often a stunted plant is produced. Damage is more common on sandy soils following periods of drought.

Wireworms: Many species

Many species of wireworms, which are larvae of click beetles, attack corn. They are about 1/2 to 1 1/4 inches long (13-30 mm), yellow-brown in color, are hard, shiny, and appear as a short piece of wire—hence their name. They bore into seed and stems of corn plants below the soil surface. Damaged seed do not germinate. Damaged plants are killed or may be stunted if they survive.


Southern Corn Billbug (Sphenophorus callosus)
Maize Billbug (Sphenophorus maidis)
and others

Billbugs are snout beetles and most are about 1/2 inch long (13 mm). They have chewing mouthparts on a "beak" or snout. Adults damage seedling corn by chewing holes into the stem at or near soil level and feed on the tissues within. This causes a wilting of the plant bud and often, death of the plants. Plants which survive are often stunted and unproductive. A typical symptom of early billbug damage is a transverse row of holes in one or more of the whorl leaves. The larvae of some species damage corn by feeding in the taproot of corn late in the season.

Sugarcane Beetle (Eutheola rugiceps)

The sugarcane beetle is hard, shiny, black and about 5/8 inch long (15 mm). It typically attacks corn in the early seedling to late whorl stage. The beetles chew large, ragged holes in the main stem just below the ground. Smaller plants may be killed outright. Plants which survive are stunted and tiller excessively (sprouting new stalks from base of plant).


Cutworms: Many species

Many species of cutworms damage corn. Cutworms are usually dull gray, brown or black in color, fat, greasy appearing and about 1 1/2 inches long (38 mm). They curl up into a tight coil when disturbed. These larvae typically attack seedling corn and cut the main stem off just above the soil surface. They feed mostly at night and burrow one or two inches down into the surface during the day.

Southern Corn Rootworm (Diabrotica undecimpunctata howardi)

The southern corn rootworm is a slender, white or cream colored larvae that may reach a length of 1/2 to 3/4 inch (13-18 mm) when mature. It has 3 pairs of inconspicuous legs. The head is dark brown to black and the last segment of the body bears a dark brown to black plate. The adult, the spotted cucumber beetle, is a greenish-yellow beetle approximately 1/4 inch long (6 mm), with 12 irregular black spots in its back. The larvae feed on the roots and underground stem of seedling corn. On larger corn, damage is primarily to the roots. Small seedlings are sometimes killed outright. Root feeding may result in a stunted, spindly plant which is subject to lodging (fall over before harvesting).


Corn Leaf Aphid (Rhopalosiphum maidis)

Many species of aphids may be found on field corn. The most common is the corn leaf aphid. This aphid is relatively large and is bluish-green. It is about 1/8 inch long (3 mm), and has two "tail pipes" or cornicles projecting from the rear end. It is often found in dense colonies on corn leaves and in the tassel. It damages corn by sucking juices from the leaves and by secreting sticky honeydew on the tassels and silks.

Southern Cornstalk Borer (Diatraea crambidoides)

The southern cornstalk borer is pinkish white, marked with conspicuous dark spots over the body, and is about 1 inch long (25 mm). It bores in the whorl and stalks of the corn plant. Infested plants are usually stunted. Leaves on the plant are sometimes ragged and broken from feeding damage when the leaves were still rolled up in the whorl.