Predation on fall armyworm (Lepidoptera:Noctuidae) in sweet sorghum

Predatory arthropod fauna was investigated to determine both composition and potential for controlling fall armyworm (Spodoptera frugiperda [J. E. Smith]) populations in sweet sorghum, Sorghum bicolor (L.) Moench. The fauna was comprised predominantly of red imported fire ants, Solenopsis invicta Buren. Predation was responsible for at least a 3-fold reduction in S. frugiperda infestation levels on whorl-stage sweet sorghum. Whorl-feeding behavior by S. frugiperda in plots with suppressed predator populations resulted in 10 to 15% plant defoliation. Post-whorl phenological stages of sweet sorghum were not attacked by subsequent generations of S. frugiperda larvae. Although significant differences were not detected, there was a 6.4% trend toward a reduction in total sugar yield in plots with higher S. frugiperda levels in 1985. However, a 72.5% reduction in S. frugiperda infestations likely prevented a repeat of this trend in 1986. Thus, early-season S. frugiperda damage to whorl-stage sweet sorghum was not found to cause significant economic losses in either year. Natural control by S. invicta was shown to be a major regulating factor in S. frugiperda population dynamics in sweet sorghum.