PREPUPAL AND PUPAL PARASITISM OF HELICOVERPA-ZEA AND SPODOPTERA-FRUGIPERDA (LEPIDOPTERA - NOCTUIDAE) BY STEINERNEMA SP IN CORNFIELDS IN THE LOWER RIO-GRANDE VALLEY

An indigenous Steinernema sp. (Rhabditida: Steinernematidae) nematode parasitized prepupae and pupae of com earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith), collected from fruiting cornfields in the Lower Rio Grande Valley of Texas and northern Tamaulipas, Mexico. Over a 5-yr period, 34% of all fields sampled contained parasitized com earworm and 24.2% contained parasitized fall armyworm. Of 3,036 com earworm prepupae and pupae collected during this study, 11.6% were parasitized; of 1,802 fall armyworm collected, 9.3% were parasitized. Parasitism by Steinernema sp. accounted for 49.4 and 46.1% of the mortality of corn earworm and fall armyworm prepupae and pupae, respectively.