Document Type

Thesis - Open Access

Award Date

1982

Degree Name

Master of Science (MS)

Department / School

Entomology

First Advisor

Burruss McDaniel

Abstract

The effect of Entomophaga grylli on grasshopper populations within South Dakota was investigated during a 2-year period. Field observations established that the state's 3 most important species of grasshoppers are susceptible to pathotype 2 infections. Outbreaks are believed to be initiated annually from the soil of undisturbed areas which act as the reservior for Entomophaga grylli resting spores. The occurrence of the fungus in regions of the state receiving 355 mm of rain during the growing season indicate pathotype 2 infection is maintained in dry environments. However, detailed epizootiol ogical studies of the fungus are needed before the potential of Entomophaga grylli, as a biological control agent, is established.Due to the possible widespread devastation caused by grasshoppers, the problem of control has been one not only of private individuals, but one of public responsibility. Federal funds are not available for spraying grasshoppers in cropland areas. However, organized control programs on rangeland have been supported by federal aid which paid one-third the total cost per acre of spraying. Nevertheless, such programs are usually crisis oriented and during the hot, dry years of grasshopper outbreaks, the benefits of using expensive chemicals is not justified from a farmer's standpoint. Management of grasshoppers in the past 3 decades has relied heavily on broad-scale application of insecticides. These insecticides are not specific for grasshoppers and will kill the natural enemies of grasshoppers as well as other beneficial insects. Many insecticides are extremely toxic, limiting their use to commercial applicators only. Also, waiting periods maybe required between the time of application and harvest or grazing of the treated area.

Library of Congress Subject Headings

Locusts -- South Dakota -- Biological control
Entomophthora
Pathogenic fungi -- South Dakota

Format

application/pdf

Number of Pages

58

Publisher

South Dakota State University

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