Publication E-83
October, 1967
Purdue University
Cooperative Extension Service
Department of Entomology

CORN INSECTS - ABOVE GROUND

1. EUROPEAN CORN BORER, Ostrinia nubilalis (Hubner). Corn borer moths emerge in spring and lay eggs on early-planted corn. Newly-hatched larvae crawl toward the stalk, feeding on leaves as they go. Many of them congregate in the plant whorl and later crawl behind leaf sheaths and bore into the stalk. When mature, these borers change into moths that lay eggs for a second generation. Most of these eggs are laid on late-planted corn and the emerging borers feed in the ears as well as bore into the stalks. In southern Indiana there may be a third generation each year. Proper timing of insecticide treatments is important. Application must be made after eggs hatch but before the young borers become deeply imbedded in the plant whorl or enter the stalk. For control, see E-17.

2. SOUTHWESTERN CORN BORER, Zeadiatraea grandiosella (Dyar). This insect, at present, does not occur in Indiana but is found in southern Illinois and western Kentucky. Its life cycle is similar to the European corn borer, except that in late summer, the Southwestern borers work their way toward the base of the stalks and overwinter in the tap root. In so doing, they girdle the inside of the stalk just above the ground level causing the corn to fall over.

3. COMMON STALK BORER, Papaipema nebris (Guenee). The common stalk borer is a general feeder and will attack almost any kind of plant with a soft stem large enough to accommodate its body. In the case of corn, damage is usually confined to field margins where the borers have moved in from weedy areas. The insect not only bores into the stalks but also feeds in the whorls of young corn, giving the plants a "chewed-up” and ragged appearance.

4. CHINCH BUG, Blissus leucopterus (Say). Chinch bug outbreaks are most likely to occur in areas around Benton and Newton counties in the west and Adams and Jay counties in the east. Dry spring weather favors development. Damage to corn will usually occur in fields adjacent to small grain, in which the spring brood (first generation) develops. As grain mamres, the bugs crawl into the border rows of corn and gradually move deeper into the field. How far they go depends on the number of bugs and size of the corn. When mature, the bugs develop wings and fly away. The second generation is widely scattered and feeds on many plants of the grass family. For control, see E-53.

5. CORN EAR WORM, Heliothis zea (Boddie).
The corn earworm may occur throughout the state, but greatest damage is caused in southern Indiana. Besides corn, it feeds on soybeans and other plants and is also known as the tobacco budworm, cotton bollworm, tomato fruitworm and vetchworm. The insect varies greatly in color, and the worms found in Indiana are often tan or brownish rather than green. There are several generations each year. Control is difficult and expensive; therefore, treatment of field corn is seldom practiced. Early planting is recommended. For control, see E-31.

6. ARMYWORM, Pseudaletia unipuncta (Haworth). The armyworm feeds primarily on plants of the grass family. And outbreaks occur only in certain years and in areas favorable for their development. Eggs are laid in. dense grassy vegetation as in pastures, small grain fields and along roadsides. As the worms mature, they leave these areas and "march” in search of food. Corn is usually
damaged during these migrations. Most outbreaks occur in the spring. Later generations are held in check by disease, insect parasites and other natural enemies. For control, see E-37,

7. CORN ROOTWORM BEETLES, Diabrotica spp.
These are the adults of corn rootworms. The beetles commonly feed on corn silk. Clipping of silks prior to pollination can result in partly barren ears. Such damage usually takes place in late-silking fields since early-planted corn is normally pollinated before many beetles emerge. The northern species is responsible for most of the damage in Indiana. The western species has not yet invaded Indiana, but the infested area is expanding eastward and may eventually reach this state. For control, see E-49.

8. GRASSHOPPERS, Family Acrididae. Grasshoppers are general feeders. Damage to corn and other cultivated crops is usually caused by those that migrate into the fields from border areas. This happens in late summer and also in dry years, when natural vegetation no longer provides a suitable food supply. Damage is often confined to the border rows. For control, see E-19.

9. CORN LEAF APHID, Rhopalosiphum maidis (Fitch). These small, soft-bodied "plant lice” cluster on the tassels and upper parts of corn plants. Heavily-infested plants may be barren or produce only partly filled ears. Most of this damage takes place before 50% of the tassels have emerged. Therefore treatments applied after tasseling are of little value. Early-planted corn usually escapes injury, and some hybrids are more tolerant than others. For control, see E-58.

10. CORN FLEA BEETLE, Chaetocnema pulicaria Melsheimer. These tiny black jumping beetles injure corn early in the season, when growing conditions are poor and when the plants are less than 4 or 5 inches tall. Larger plants outgrow the damage. Heavily-infested plants turn greyish in color, and the leaves shrivel and die. Pale-striped and other species of flea beetles can cause similar damage. For control, see E-48.

Current Control Information
The information and color illustrations presented here are designed to help you correctly identify some of the more common insects that attack corn above ground. These insects and the problems they cause do not change, but methods of dealing with them do. Therefore, Purdue University extension entomologists have prepared the following publications to keep you up to date on the latest recommended control methods and materials:

E-17 "Corn Borer Control”
E-19 "Grasshopper Control”
E-31 "Corn Earworm Control”
E-48 "Cutworms and Flea Beetles in Corn”
E-49 "Soil Insects Affecting Corn”
E-53 "How to Control Chinch Bugs”
E-57 "How to Control the Armyworm”
E-58 "The Corn Leaf Aphid”

Single copies of these publications, revised periodically, may be obtained by Indiana residents, free of charge, from their local County Extension Office, or from the Agricultural Publications Office, AES Building, Purdue University, Lafayette, Indiana 47907.
10/67 (10M)
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S Department of Agriculture Cooperating. H. G. Diesslin, Director, Lafayette, Ind. Issued in furtherance of the Acts of May 8 and June 30, 1914.