It is likely that several species of Cyclocephala (annual life cycle) or Phyllophaga (three-year life cycle) can be found in wheat fields in the Great Plains. White grubs are the immature stage of scarab beetles (Cyclocephala—chafer beetles; Phyllophaga—May or June beetles). White grubs are recognized by their white body color, brown head capsule, and C-shaped body.
Over 30 insect and mite species attack wheat in the United States of America. Most rarely cause damage to wheat or occur in localized areas, and therefore, are of minor economic significance. In the Great Plains, the greenbug (Schizaphis graminum) (Figure 1.3) and Russian wheat aphid (Diuraphis noxia) (Figure 1.4) are major pests that frequently cause damage to wheat over large parts of the region. When outbreaks occur, they must be managed to avoid significant yield losses.
There are many species of flea beetles, each feeding on different types of plants. Some species feed on wheat when their primary plant food plant such as corn or sorghum dissapears, which is the case of corn flea beetle.
This moth does not overwinter in Kansas but migrates northward annually from southern states. It usually arrives in Kansas in July where it lays eggs on corn, sorghum and other summer crops. Reproduction may continue through August and into September, putting earlyplanted wheat at greatest risk. Early-planted fields should be inspected frequently during the first few weeks following emergence. The first sign of damage is “windowpane” injury caused by tiny larvae chewing on seedling leaves.
Adult moths emerge from the soil in late summer and fall. They are light gray in color with indefinite markings and a wingspan of about 1 1/4 inches. Eggs are deposited in loose, dry, sandy or dusty soil. Thus, larvae are usually found most easily in the driest parts of the field, such as hilltops. Eggs usually hatch in very early spring and larval damage often becomes noticeable about the time the wheat begins to joint in March or April. The pale western cutworm is a subterranean cutworm, feeding on the stems of the crown just below the soil level.
Army cutworms produce a single generation per year. In Kansas, sexually immature army cutworm moths migrate westward to the Rocky Mountains, typically beginning in early May and continuing until the first days of summer. Moths feed and become sexually mature by summer’s end and initiate their fall migration eastward to the High Plains beginning in mid-September. Female moths (each capable of producing between 1,000 and 3,000 eggs) deposit eggs on the soil surface or beneath dirt clods, typically in areas next to suitable host plants.
Adults are tiny (1.5-2.5 mm long) with orange-red bodies that resemble mosquitos. Larvae, the damaging life stage to wheat, are also tiny and white to orange in color. Larvae actively feed in moist conditions during early summer and continue feeding for several weeks. Larval feeding can damage developing kernals and reduce yield. Feeding damage also increases the chances of fungal infections of wheat heads.
The larvae of cereal leaf beetle feed on emerge and feed on wheat foliage in late spring and early summer.
High temperatures and dry conditions in spring and summer increase population numbers of cereal leaf beetles.
Larvae feed on leaf tissue between leaf veins, causes long narrow slits in leaves.
Adults range in size (1/6-1/3-inch long) and have dark bodies with bulging eyes on the sides of their head and cream-colored margins around the abdomen (but should not be confused with the beneficial insect, minute pirate bug, which also has bulging eyes). The forewings are dark and relatively slender compared to other true bugs. Immature black grass bugs are smaller than the mature adults, and lack wings.