The Chinch Bug

Claude Wakeland.

Chinch bug.

The chinch bug is widely distributed in the United States but rarely is it abundant enough to cause serious crop losses except in Illinois,. Indiana, Iowa, Kansas, Missouri, Ohio, Nebraska, Oklahoma, and Texas. It occasionally damages crops in Michigan, Minnesota, Wisconsin, South Dakota, North Carolina, and South Carolina. The chinch bug increases rapidly under favorable weather conditions. In outbreak stages it is one of the most completely destructive insects to corn and sorghum plants in the United States.

Chinch bug adults in the fall fly from cultivated crops to bunchgrasses, where they rest during the winter. In spring they fly to fields of small grain in the cooler areas of their habitat or directly to corn and sorghums in the warmer areas, such as in Texas and southern Oklahoma. After reaching cultivated fields, they mate and lay their eggs on the leaves of the plants or on the soil near the bases of the plants. After the eggs hatch, the young bugs feed on the plants and, in grainfields, most of them crawl to nearby crops such as corn and sorghum when grain plants lose their succulence or begin to ripen. A second generation usually is produced while bugs infest corn or other susceptible crops, and the adults from this generation fly to bunchgrasses for the winter.

The bug feeds by sucking the juices of plants. When the insects crawl from grainfields they concentrate on the outer rows of young corn or sorghum plants, which soon wilt and die. As the outer rows are killed, the bugs migrate inward until an invaded field becomes infested throughout. Chief reliance for protection of cornfields from bugs invading them from grain fields is placed upon the use of barriers to intercept migrations or to kill migrating bugs before they can reach susceptible crops.

When the overwintering adults fly directly from bunchgrasses to corn, the entire cornfield may be infested more or less uniformly. An economical and practical control has not yet been established to cope with that situation.

Chinch bugs feed successfully only on plants of the grass family. In years of severe infestations, when their normal food plants become scarce, they may try to feed upon legumes or other nongrass plants, but only rarely in numbers sufficient to cause injury.

Particularly susceptible among the small grains are barley, spring and winter wheat, rye, and oats. Barley is especially preferred and so is a hazardous crop to grow during a period of chinch bug outbreaks.

Most favored of the larger crop grasses are corn, sorghums, broomcorn, Sudangrass, and millet. Young corn plants are choice food for the bugs.

Chinch bugs also feed upon many forage and wild grasses, including fox-tail, timothy, crabgrass, kafircorn, quackgrass, and ticklegrass. Bentgrass, bluegrass, and other lawn grasses may be attacked.

CONDITIONS PERMITTING, the most economical and effective way to prevent losses from chinch bugs is by crop rotation and by the location of susceptible crops with relation to small-grain fields. The first generation of chinch bugs, except in the southern part of their habitat, depends at first on small grains for its food; second-generation bugs feed mainly on corn and sorghums. Eliminating or reducing acreages of grain crops or avoiding planting susceptible crops near small-grain fields materially scales down losses due to chinch bugs.

Legumes and other practically immune crops may be substituted to advantage for small grains or corn and sorghums during years of threatening outbreaks. Crops that may be grown without danger of serious injury by chinch bugs include alfalfa, beans, buckwheat, alsike clover, red clover, sweetclover, cowpeas, field peas, flax, lespedeza, peanuts, potatoes, pumpkins, rape, soybeans, squash, sugar beets, sunflowers, velvetbeans, vetch, and other field, garden, and truck crops not belonging to the grass family. During years of severe infestations, the farm cropping scheme should be so adjusted as to avoid, or reduce to a minimum, the planting of corn or sorghums next to small-grain fields. If it is impracticable to substitute immune crops for grains, injury may be lessened by planting some of the least susceptible or resistant varieties.

Hybrid corns and sorghums have been developed that have some resistance to second-generation bugs. Ruined fields of corn, sorghums, or small grains should be disked or plowed to destroy the bugs and replanted with an immune crop. Early planting of grains, corn, and sorghums helps to reduce injury. Chinch bugs are attracted more to thin stands of grain than they are to rank growth. All tillage, fertilization, and seeding practices that promote a vigorous growing grain crop therefore tend to lessen damage. Small-grain fields, with a dense growth of clover, which causes a damp, shady condition, also are unattractive to the bugs.

IN PREPARING TO COMBAT chinch bugs, surveys in the fall give a pretty good idea of how many to expect the following season and where they are most likely to be found.