Establishment of Oomyzus gallerucae (Hymenoptera: Eulophidae), an egg parasite of the elm leaf beetle (Coleoptera: Chrysomelidae), in Missouri and adjacent states

The non-indigenous elm leaf beetle (ELB), Xanthogaleruca luteola (Muller), egg parasite Oomyzus gallerucae (Fonscolombe) was first recorded from Boone County, Missouri, in 1989. It has since been recorded in 55 additional Missouri counties and 5 adjacent states. Parasites were not detected in an additional 14 Missouri counties. Annual parasitization from ELB egg masses sampled at Columbia, Missouri, ranged from 26.3 to 51.7%. O. gallerucae was reared from egg masses on the first collection date each year as well as the last, indicating that the parasite successfully overwinters each year and is synchronized with the phenology of the beetle. The 38.0% overall mean rate of parasitization in addition to mortality resulting from host feeding of the eggs appeared to inhibit conspicuous leaf damage. The delayed establishment and dispersal of O. gallerucae is compared to similar circumstances of three other parasites (e.g., Collyria calcitrator (Gravenhorst), Bathyplectes tristis (Gravenhorst), and Patasson nitens (Girault)). The presence of O. gallerucae in Missouri has potentially contributed to the decline of the ELB as an urban pest in the state.