ABSTRACT
The relationship of sorghum, sorghum midge, and johnsongrass is examined in terms of biologies, origin and transport, population dynamics, and management. Johnsongrass is a stout, erect, perennial grass that spreads by seeds and by long creeping rhizomes. Johnsongrass is a very heavy seed producer; however, its superior ability to compete with other plants and its persistence in the face of the most intensive control measures surely result from the long, very vigorous, and highly adaptable rhizome-root system. Most likely, johnsongrass resulted from the wild Arundinacea and S.propinquum, followed by chromosome doubling. Fundamental to the description of the association of sorghum, johnsongrass and sorghum midge is the construction of a seasonal dynamics model. Johnsongrass constitutes the host for the first generation as well as a second generation that is produced before cultivated sorghum begins to flower. Sorghum midge, Contariniasorghicola, and host grasses of the genus Sorghum constitute a naturalized system in North America of seemingly permanent success that directly affects agriculture.
