Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School



There has been much research since the tum of the century devoted to the biology of the greenbug (Schizaphis graminum Rond.) and the feeding damage to winter wheat caused by this insect. In recent years a new green bug biotype has emerged that can with stand high temperatures and produces economic damage on sorghum during the late summer months. In 1968, several million acres of grain and forage sorghum were extensive by damaged by the greenbug in the Great Plains states of Texas, Oklahoma, Arizona, Nebraska, Colorado, Kansas, and South Dakota. In the northern Great Plains, a limited number of acres of newly emerged winter wheat were also damaged by the greenbug. The fact that the growing seasons of sorghum and winter wheat overlap, indicates that a possible source of greenbug infestation exists for winter wheat. The new biotype became a major concern of entomologists in the Midwest. A conference was called in Oklahoma on November 7, 1968. The United States Department of Agriculture and various state agencies from the affected areas met to outline projects of study on the greenbug and its relationship to crops. The majority of the proposed research was oriented to greenbug sorghum interrelationships and not to the problem of effect of greenbug infestations to winter wheat production in the northern Great Plains, and South Dakota in particular. One of the factors which made this a unique problem of the northern plains was cool temperatures which generally occur in the fall. Greenbug predator and parasite populations decline during the cool weather winter wheat growing season, while the greenbug population maintains its vigor. Natural biological control of the aphid population becomes less effective resulting in proportionately higher populations of greenbugs with resultant damage to the winter wheat. This study investigates the effect of cool temperatures on the two strains or biotypes of greenbugs found in South Dakota. Although data existed from previous investigations on the biological parameters of the greenbug under cool conditions, much of the information was contradictory and did not include data of the new biotype discovered recently on sorghum. This study is primarily concerned with finding some indication of the extent of the potential problems that might be encountered on fall plantings of wheat in South Dakota due to this new biotype.

Library of Congress Subject Headings

Beneficial insects
Insect pests



Number of Pages



South Dakota State University