Abstract The entomopathogenic nematode Steinernema riobravisCabanillas, Poinar and Raulston (Rhabditida: Steinernematidae) was evaluated for inundative biological control of Helicoverpa zea(Boddie) (Lepidoptera: Noctuidae) in Arkansas corn fields. Infection of H. zeawas highly significant in nematode-treated plots of field corn and sweet corn in Little River and Washington Counties, respectively. Mean mortalities from S. riobravisinfections were 79.2 and 91.3% at treatment levels of 3.7 × 10 6and 1.2 × 10 7nematodes/m 2of soil, respectively, in Little River County and 78.5 and 94.8% at treatment levels of 5.2 × 10 5and 5.3 × 10 6nematodes/m 2of soil, respectively, in Washington County. Comparison of irrigated and nonirrigated plots in both counties resulted in no significant differences in S. riobravisinfecting H. zea. S. riobravismay have promise as an inundative biological control agent against H. zeain Arkansas soils.