During a 5-year period from 1954 through 19.58, approximately 17,844 acres of Illinois farm land near Sheldon were treated with 2 and 3 pounds of dieldrin per acre for suppression of a local infestation of Japanese beetles (Popillia japonica Newm.). Surveys conducted each year in field corn showed that more European corn borers (Pyrausta nubilalis (Hbn.)) were present in fields within tile treated area than in fields surrounding it. During IBM and 1!l55, when corn borer populations were very high, fields within the suppression area averaged 2.6 more borers per infested stalk of corn than fields outside of the treated area. During 1955, field corn growing within the treated area was slightly more attractive to the corn borer for egg deposition and for survival of borer larvae. Although more egg masses were laid and more corn borers survived in fields in the treated area, the slightly increased attractiveness of the corn in treated fields does not completely account for the great difference in number of European corn borers found in treated and untreated fields. Some predators commonly found in cornfields were not adversely affected by the dieldrin. The corn borer parasitc, Lydella grisescens R.-D., as well as some other common predators were equally abundant in the treated and untreated study areas. The factors responsible for the increase in number of European corn borers in the large, dieldrin-treated, .Japanese beetle suppression area at Sheldon, Illinois, were not definitely ascertained. The data presented tend to indicate that the size of the treated area was. important and in some way contributed to the increase in number of corn borers which increase was not great enough to warrant additional control measures.
Document Type: Research Article
Publication date: August 1, 1960
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