 General Practices
Wheat is grown throughout Illinois but is more commonly grown in the southern one-third of the state. The longer season available in the region below I-70 makes it possible to follow-up the late June or early July wheat harvest with a double-crop of soybeans if sufficient soil moisture is available. The soft red winter wheats are sold to some specialized local elevators or are sold to
domestic or foreign markets.
Insect Pests
Insect pests in the Illinois wheat crop are not monitored. There is no reliabillity for any state data. The insects listed below bring the most damage. The Bird Cherry-oat Aphid and the Hessian Fly also carry disease vectors and are therefore included in this list.Armyworms3,4 Adults moths migrate into Illinois each spring; the female moths lay eggs in grasses and wheat. The larvae feed on the grasses until completion of larval development, then pupate in the soil. Moths emerge in early summer, mate, and lay eggs. Armyworm larvae may strip the leaves off the
stem and chew through the stem beneath the grain head. There are usually two to three generations per year, but the migrant population in the spring is usually the most destructive. Conditions that suppress parasitoid populations, such as cool, wet weather or drought, are favorable for army worm
infestations. In outbreak years, as much as 50 percent of the wheat in southern Illinois has been treated with insecticides, but on average, very few acres are treated for armyworm control. Treatment is justified when there are 6 or more nonparsitized larvae per foot of row.Bird Cherry-Oat Aphid7 The bird cherry-oat aphid ranges in color from orange-green to dark green,
and sometimes even greenish-black. The most common time of year to see the aphid is in February or March. When the aphids attack the wheat, they can cause a golden yellow streaking on the leaves. Occasionally heavy populations cause the flag to curl up in a tight cork-screw fashion that may trap the awns, resulting in a fish-hook appearance to the head. A combination of predators and parasites can usually keep the aphids under control. This method should be concidered before a chemical control.
Cereal Leaf Beetle Adult cereal leaf beetles are about 3/6 inch long and have metallic looking heads and wing covers. The legs and front of thorax are brownish-red. Adults overwinter in fallen leaves, ground litter, or other debris. They lay eggs in the spring. Eggs hatch in about 5 days and Larvae develop in 10-12 days after that. Regular feeding habits do not affect the growing plant. The wheat becomes severely defoliated only when a conciderable amount of green tissue is lost on the upper leaves. Severe defoliation is recognized by a white frosty look.
Grasshoppers, Differential 4 (Melanoplus differentialis) Migratory (M. sanguinipes) , Redlegged (M. femurrubrum) , and Twostriped (M. bivitatus) Grasshoppers overwinter as eggs in the soil. Nymphs hatch in the spring and feed for several weeks, usually completing their development by mid-summer. Adults feed throughout the remainder of the summer. Grasshoppers thrive during hot, dry summers when naturally occurring pathogens are suppressed, and tend to be more numerous the year after a drought. Grasshoppers prefer to feed on weeds, but when these are unavailable, they will move readily into crop fields. The amount of insecticide use varies, but during outbreak years up to 11% of field
edges are treated.Hessian Fly 3,4 Hessian flies overwinter as puparia at the base of wheat plants. Adults emerge in April and deposit eggs on wheat leaves. After hatching, the larvae move immediately to a position between the leaf sheath and the stem. Larval feeding occurs from 2 to 6 weeks, after which the larvae pupate into a case-like puparium. In late summer through early fall, a second generation
emerges. Females lay eggs on the leaves of young plants or volunteer wheat. Larvae mature to the
pupal stage by mid-autumn and overwinter as puparia. Conditions that favor infestations of Hessian fly are wheat planted too early in the fall, the presence of volunteer wheat, and abundant acres of wheat varieties susceptible to attack by Hessian fly. Hessian flies have overcome the latest
tolerance/resistance genes in most varieties and the pest threatens to become a major problem again. However, the "fly-free" planting dates help avoid damage caused by newly-emerged adult Hessian flies
in the fall. If the crop does not emerge until after egg-laying females have died, fall-sown wheat
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