Biology of an Adventive Population of the Armored Scale a Biological Control Agent of in California.

(giant reed) is invasive in Mediterranean, sub-, and tropical riparian systems worldwide. The armored scale is approved for biocontrol in North America, but an adventive population was recently discovered in southern California. We documented this population's distribution, phylogeny, phenology, potential host spillover to ., and potential for parasitism by a common biocontrol parasitoid of citrus scale. The adventive scale was found within a single watershed and is genetically closest to Iberian scale genotypes. developed on haplotypes but at much lower densities than . The adventive population is univoltine, producing crawlers from March-June. parasitoids exhibited sustained interest in during choice and no-choice trials and oviposition resulted in a small second generation. appears limited in distribution by its univoltinism and sessile adult females. This presents challenges for broad biocontrol implementation but allows for targeted application. The genetic differentiation between imported biocontrol samples and adventive populations presents an opportunity for exploring benefits of hybrids and/or alternative genotypes where establishment has been difficult. While unlikely to occur in situ, spillover to vulnerable endemic or deleterious parasitoid effects on scale biocontrol agents warrants consideration when planning use of .