Document Type

Thesis - Open Access

Award Date

1972

Degree Name

Master of Science (MS)

Department / School

Entomology-Zoology

Abstract

The greenbug, Schizaphis graminum (Rondani), is a major pest to grain crops in the Great Plains states. In 1968, 7.3 X 106 acres of sorghum were infested in nine of these states. The loss of sorghum in Kansas alone was estimated at lJ.5 X 106 bushels. In 1969 and 1970 the combined South Dakota recorded sorghum yield and control losses were over $2.6 X io6 (USDA 1970 and 1971). The greenbug is an economic vector for diseases of winter wheat, barley, oats, sorghum, and cane. Severe infestations on winter wheat have led to reduced crop cover and soil erosion. S. graminum has evolved three biotypes, A, B, and C. Biotype C has been one of the main limiting factors to grain production, thriving over a wide temperature and plant host range. The greenbug has migrated northward to the central states each spring. There has been a natural time lag which has enabled establishment of the greenbug between its entrance in April and the parasite-predator build-up. Greenbug populations have been effectively reduced by topical applications of chemicals, often harsh to natural controls and poorly timed. Systemic insecticides are being tested for early, preventative and residual control. Such insecticides will possibly be less damaging to native greenbug predator and parasite populations, allowing their build-up while suppressing the greenbug numbers. A combination of biological and chemical controls may be the solution to improved production. The objectives of this project were to contribute to the knowledge of the biology of Lysiphlebus testaceipes (Cresson), considered to be an effective control of the greenbug, and to investigate the influence of certain systemic insecticides in sorghum, on the greenbug populations and on the greenbug predator and parasite populations. The influence of low temperature on successful parasite copulation and emergence was investigated under controlled environmental conditions, and the population studies, under field conditions.

Library of Congress Subject Headings

Greenbug -- Control
Hemiptera
Beneficial insects
Insect pests
Agricultural pests

Format

application/pdf

Number of Pages

196

Publisher

South Dakota State University

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