Growth and Yield of Grain Sorghum Infested in the Whorl with Fall Armyworm12

Abstract

In tests conducted during 1957, 1960, and 1962 to determine the effect on yield of RS 610 sorghum when plants were infested during the whorl stage with the fall armyworm, Spodoptera frugiperda (J. E. Smith), reductions in yield of 19.6, 5.4, and 10.4%, respectively, were obtained for the 3 years. During 1962 a combined infestation of the fall armywonn and southwestern corn borer, Zeadiatraea grandiosella (Dyar), resulted in a reduction in sorghum yield of 27.2%. Yield losses from the fall armyworm alone apparently were caused by smaller, rather than fewer, kernels per head in the infested plants. When plants were infested by both species, the heads contained fewer as well as smaller kernels. The reduction in kernel size, and in the number of kernels per head, was apparently associated with delayed emergence of the head from the boot, which prevented normal growth, especially at the base of the head. It is possible that this condition is entirely associated with late planting, but the fall armyworm in this area usually reaches economic numbers on sorghum only in late plantings.