Pheromone Race Composition of Ostrinia nubilalis (Lepidoptera: Crambidae) and Larval Co-Occurrence with Sesamia nonagrioides (Lepidoptera: Noctuidae) in Maize in Central-Eastern Italy

Ostrinia nubilalis (Lepidoptera: Crambidae) and Sesamia nonagrioides (Lepidoptera: Noctuidae) are major maize pests in the central-eastern Mediterranean area, responsible for both quantitative and qualitative yield losses. This study investigated the corn borer species present in central-eastern Italy, the presence and prevalence of O. nubilalis pheromone races, and the within-plant larval distribution. Traps baited with E, Z, or E/Z pheromone lures were used to investigate O. nubilalis pheromone races, while 596 maize plants were sampled at harvest and dissected to determine species composition, relative abundance, and larval distribution across three plant sections (lower and upper stalk and ear). Males were captured in traps baited with each pheromone lure, with no significant differences among catches. Larval sampling revealed the co-occurrence of O. nubilalis and S. nonagrioides, with O. nubilalis being the prevalent species. For both species, larvae were significantly more abundant in the lower plant section, and co-occurrence did not appear to influence their within-plant distribution. Comparing the species-specific larval distribution, a significantly higher proportion of S. nonagrioides occurred in the lower plant section, whereas O. nubilalis was significantly more frequent in the ears. However, the presence of both species in the ears highlights the need to consider both pests in management. These findings highlight the importance of monitoring activities in the area, using traps baited with each pheromone lure for O. nubilalis. Knowledge of the co-occurrence between the two species can be considered fundamental for developing Integrated Pest Management strategies, as it can influence the timing and effectiveness of control methods.