The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is the most important insect pest of collard, Brassica oleracea var. acephala de Condolle, in South Carolina. In 1997 and 1998, studies were conducted on diamondback moth larval and pupal population density and parasitism by Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), in collard fields in South Carolina.. The density of diamondback moth larvae generally increased from below the economic threshold early in collard crop growth to above the economic threshold as crop growth progressed. Host density ranged from 0 to 9.28 diamondback moth larvae and pupae per plant. Data suggest that all sites would have required additional strategies to control the diamondback moth populations. Diadegma insulare was the major parasitoid of diamondback moth, and parasitism ranged from 0 to 58.5%. Diamondback moth was also parasitized by Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae). Parasitism by O. sokolowskii started later in the season than parasitism by D. insulare, usually when the diamondback moth population was at or above the economic threshold. Parasitism by O. sokolowskii ranged from 0 to 7.3%. Parasitism by 1). insulare and O. sokolowskii was inadequate to maintain diamondback moth populations below the economic threshold in commercial collard fields in South Carolina. Plutella xylostella (Plutellidae) : Host Diadegma insulare (Ichneumonidae) : Parasite Oomyzus sokolowskii (Eulophidae) : Parasite Nutrition; Diet; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics; Land zones; Nearctic region; North America; USA Diadegma insulare; Oomyzus sokolowskii; Lepidopteran hosts; Seasonal prevalence related to host population dynamics; Plutella xylostella; South Carolina; Lexington County Plutella xylostella; Food plants; Brassica oleracea var. acephala; Hymenopteran parasites; Parasites seasonal prevalence related to host population dynamics; Diadegma & Oomyzus; Population density; South Carolina; Lexington County none