Performance of a Native Butterfly and Introduced Moth on Native and Introduced Lineages of Phragmites australis

SIMPLE SUMMARY: We evaluated the survival and development of a native butterfly (Poanes viator) and introduced moth (Rhizedra lutosa) fed native or introduced lineages of common reed (Phragmites australis). The native butterfly feeds more generally on monocots, so some larvae were also fed wild rice (Zizania aquatica). Using R. lutosa, we also tested an artificial diet supplemented with common reed rhizome powder as a potential food for rearing stalk and rhizome boring Lepidoptera. Generally, both insect species had low larval survival on all plants used, but high pupation success once insects reached that stage. Only P. viator larvae reared on leaves from native plants pupated and completed development. Rhizedra lutosa completed all developmental stages on native and introduced P. australis rhizomes. The artificial diet resulted in a doubling of survival and successful development to adults for R. lutosa. Several specialist Lepidopteran species are being considered for approval as biological control agents for the non-native, invasive common reed in North America, and the convenience and increased larval performance make this artificial diet a good alternative for rearing organisms. ABSTRACT: This study examined the performance of Poanes viator (Edwards) (Hesperiidae), a native North American skipper, and Rhizedra lutosa (Hübner) (Noctuidae), an introduced moth, reared on native and non-native, invasive lineages of Phragmites australis. Poanes viator is a generalist on monocots and larvae were also fed leaves of Zizania aquatica, a native macrophyte that the skipper commonly uses as a host plant. Larval survival and duration, pupal weight, and pupation time were compared for P. viator feeding on leaf tissue and R. lutosa feeding on rhizomes of either native or introduced plants. We also tested an artificial diet supplemented with P. australis rhizome powder as a potential food for rearing other stalk and rhizome boring Lepidoptera. In experiments using excised plant tissues, some individuals of both species fed and developed to the pupal stage on native and introduced plants, but overall, larval survival rates were low. Plant species/haplotype identity did not cause strong differences in larval survival for either species. However, P. viator larvae only pupated when feeding on native plants (Zizania aquatica and native P. australis haplotypes), whereas R. lutosa successfully pupated on both native and introduced P. australis. Although larval survival was low, 100% of P. viator and 95% of R. lutosa that reached the pupal stage emerged as adults. Rhizedra lutosa larvae fed an artificial diet supplemented with P. australis rhizome powder had significantly greater survival and pupal weights, and shorter pupation times than larvae fed rhizomes only. Several specialist Lepidopteran species are being considered for approval as biological control agents for the non-native P. australis haplotype, and the convenience and increased larval performance make this artificial diet a good alternative for rearing organisms.