Exploratory surveys in Taiwan of the roseau cane scale Nipponaclerda biwakoensis Kuwana (Hemiptera: Aclerdidae) and its associated parasitoids

Authors: CORTEZ, A - Chung Hsing University; CHU, C - Chung Hsing University; BROADLEY, H - Animal And Plant Health Inspection Service (APHIS); LO, Y - Chung Hsing University; CHEN, Y - Chung Hsing University; Gates, Michael; MEYERSON, L - University Of Rhode Island; Hoelmer, Kim; GOULD, J - Animal And Plant Health Inspection Service (APHIS); HWANG, S - Chung Hsing University

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2022
Publication Date: 2/11/2022
Citation: Cortez, A., Chu, C., Broadley, H., Lo, Y., Chen, Y., Gates, M.W., Meyerson, L., Hoelmer, K.A., Gould, J., Hwang, S. 2022. Exploratory surveys in Taiwan of the roseau cane scale Nipponaclerda biwakoensis Kuwana (Hemiptera: Aclerdidae) and its associated parasitoids. Journal of Applied Entomology. 146(5): 596-606. https://doi.org/10.1111/jen.12982.
DOI: https://doi.org/10.1111/jen.12982

Interpretive Summary: Roseau cane is a key plant in the Mississippi River Delta coastal region, where is helps protect marshes from erosion and storm impacts and maintain shipping channels and oil infrastructure. Widespread roseau cane dieback and thinning was first noted in 2016, which has become a serious problem. The invasive Asian roseau cane scale insect has been implicated in these diebacks. To provide a safe, cost-effective, and long-term approach for managing this invasive scale, biological control methods are being considered. Documenting the natural enemies of the scale insect in Asia is the first step in this process. We investigated the population dynamics of the cane scale and its associated parasitoids on cane stands in Taiwan and documented their relative importance on scale mortality. This information will aid in developing biological control as a management tool.

Technical Abstract: Roseau cane (Phragmites australis) is the dominant plant species of the Mississippi River Delta in Louisiana, USA, and protects marsh communities from erosion and storm-related impacts, maintaining shipping channels and oil infrastructure. Widespread dieback and thinning of P. australis were noted in the Mississippi River Delta in the fall of 2016. Invasive populations of the roseau cane scale (Nipponaclerda biwakoensis), which is native to Asia, were found in outbreak levels in the stands. Subsequent research has implicated N. biwakoensis in the diebacks. To provide a safe, cost-effective, and long-term approach for the management of this invasive scale, classical (or importation) biological methods are being considered. As the first step to developing biological methods, research evaluating the natural enemies of the N. biwakoensis in the native range is necessary. This study investigated the population dynamics of the N. biwakoensis and its associated parasitoids on P. australis in Taiwan. The seasonal changes of four parasitoids attacking N. biwakoensis were evaluated over the growing season from July to November 2019 at five different study sites on the western coastline of Taiwan. The scale densities increased over the season and peaked in September (125.04±9.56 immature and mature scale per stem). The parasitism rate of the immature scales was overall low (2.25%) and was highest at the end of the growing season. An average of 14.50% adult female scales was parasitized and parasitism was highest in July. Four gregarious endoparasitoid wasp species were collected and identified as Astymachus lassalei, Boucekiella depressa, Neastymachus japonicus, and Aprostocetus sp. Astymachus lassalei was the dominant wasp species parasitizing immature scales and N. japonicus was the dominant species parasitizing adult female scales. Regardless of the scale’s life stages, multiparasitism frequently occurred between A. lassalei and B. depressa. Overall, this study provides information on the identity and role of parasitoids of N. biwakoensis in its native range, which will aid in developing a potential classical biological control as a management tool for the invasive N. biwakoensis.