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

Abstract

Roseau cane (Phragmites australis (Cav). Trin. ex Steud.) is the dominant plant species of the Mississippi River Delta in Louisiana, USA, and protects the coastline 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 Kuwana), which is native to Asia, were found at outbreak levels in the stands. Subsequent research implicated N. biwakoensis in the diebacks. As a safe, costeffective and long-term approach for managing this invasive scale, classical (importation) biological control methods are being considered. As the first step to developing biological control, research evaluating the natural enemies of the N. biwakoensis in the native range is necessary. This study investigated the population dynamics of N. biwakoensis and its associated parasitoids on P. australis in Taiwan from July to November 2019 at five study sites. Scale densities across sites increased over the growing season, peaking in September at 85.77 ± 6.36 scales/stem, which is half as dense as found in Louisiana. Mean parasitism of adult female scales across sites and season was 14.00%, while parasitism on immature scales was lower (3.00%). Four parasitoid wasp species were reared from the scale-Asytymachus lasallei Noyes and Higashiura, Boucekiella depressa Hoffer, Neastymachus japonicus Tachikawa and Aprostocetus sp.Westwood. Neastymachus japonicus was the dominant species parasitizing adult female scales, while A. lasallei was the dominant wasp species parasitizing immature scales. Astymachus lasallei and B. depressa were frequently reared from the same individual host, suggesting multiparasitism or hyperparasitism. Overall, this study provides important information on the identity and role of parasitoids of N. biwakoensis in its native range, which will aid in developing a classical biological control programme for the invasive N. biwakoensis.

Bird predation on Roseau cane scale as revealed by a web image search and querying a citizen monitoring database

“…Recently however, the widespread dieback of the common reed stands has occurred and has been found to be associated with the invasion of Roseau cane scale Nipponaclerda biwakoensis Kuwana (Hemiptera: Aclerdidae), which is native to East Asia (Cronin et al, 2020; Knight et al, 2018; Schneider et al, 2022). Several species of parasitoid wasps attacking Roseau cane scale have been recorded from the native range, including Japan (Kaneko, 1995), mainland China (Noyes & Higashiura, 2020), and Taiwan (Cortez et al, 2022). A subset of species is also found adventively in the invasive range of Roseau cane scale in the Mississippi River Delta (Knight et al, 2020).…”

Enhancing natural enemy performance through plant secondary metabolites: The role of caffeine for the parasitoid Snellenius manilae

“…For instance, biological control is one such method that involves using natural enemies to reduce pest pressure (e.g. parasitoids) (Cortez et al., 2022). However, the ability of parasitoids to control pests is limited by the availability of nutritional food resources (Bianchi & Wäckers, 2008).…”