Document Type

Dissertation - Open Access

Award Date

1973

Degree Name

Doctor of Philosophy (PhD)

Department / School

Entomology

First Advisor

Vernon M. Kirk

Abstract

False wireworms were important pests of wheat on the Great Plains during the early 20th century. Until recently, they were of little importance; however, they are now occasionally appearing in damaging proportions. The purpose of studying the biological and ecological aspects of these insects in South Dakota was to understand the factors responsible for their demise and the circumstances that could affect the recurrence of damaging populations. The more common species of false wireworms found in South Dakota during this study were Eleodes suturalis (Say), E. opaca (Say), E. hispilabris (Say), E. tricostata (Say), E. extricata (Say), E. obsoleta (Say), and Embaphion muricatum Say. The laboratory and field life history studies revealed that Eleodes suturalis, E. opaca, and Embaphion muricatum were potentially the most important false wireworm pests of wheat in South Dakota. Distribution of these species was closely correlated to well-drained elevated areas such as ridges and knolls. Eleodes suturalis was found most prevalent along the edges of fields, and E. opaca was distributed generally within the field but at some distance from the edge. Early workers described infestations of false wireworms as being restricted to light sandy soils, and this study substantiated this fact for most species. However, E. opaca was found more abundantly in heavy clay soil types; E. suturalis was commonly found in clay, loam, and silt as well as in sandy soils; and Embaphion muricatum was observed nearly as often in loam soil areas as in sandy soils. The deleterious effects of seleniun (a component of clay soil in South Dakota) were not evident when the response of Eleodes opaca to it was measured. The growth rate of E. hispilabris, which is rarely found in clay soils, was affected by high levels of selenium. Thus, selenium was implicated as a factor in clay soils that may limit the distribution of certain false wireworm species in South Dakota. Attempts to determine the economic threshold of E. suturalis by artificial infestation with laboratory-reared insects were generally unsuccessful. Populations necessary to substantially reduce yield were more than 10 times higher than naturally occurring damaging populations. Food preferences of E. suturalis and Embaphion muricatum revealed that both species fed readily on seeds of most crop plants, and that the seeds of introduced plants were more severely damaged than those of native grasses. Seeds of some species were not attacked before germination, but as these seeds germinated, they became very susceptible to attack. Eleodes suturalis, E. opaca, E. hispilabris, E. extricata, E. obsoleta, and Embaphion muricatum were successfully mas reared in the laboratory, and several cultures of these insects have been provided to scientists in the United States and England. The life cycles of all species studied extended into 2 cropping seasons. If wheat was not grown on the same ground in consecutive years, the life cycle of these insects would be broken. This cropping sequence is interrupted by a cultural practice referred to as summer-fallowing. The result has been a prevention of high populations developing within fields. As crop prices, land value, and taxes rise, there is a tendency for growers to forego this cultural practice and to grow wheat continuously in the same field. The result in recent years has been an increase in damage by false wireworms. Because of the economic and agronomic changes presently occurring, this group of insects could again become very important in the growth of wheat.

Library of Congress Subject Headings

False wireworm -- South Dakota
Wheat -- Diseases and pests
Tenebrionidae
Eleodes
Beetles -- South Dakota

Format

application/pdf

Publisher

South Dakota State University

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Entomology Commons

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