The Biology of Casmara subagronoma (Lepidoptera: Oecophoridae), a Stem-Boring Moth of Rhodomyrtus tomentosa (Myrtaceae): Descriptions of the Previously Unknown Adult Female and Immature Stages, and Its Potential as a Biological Control Candidate.

Abstract

Simple SummaryRhodomyrtus tomentosa is a perennial woody shrub throughout Southeast Asia. Due to its prolific flower and fruit production, it was introduced into subtropical areas such as Florida and Hawai’i, where it is now naturalized and invasive. In an effort to find sustainable means to control R. tomentosa, a large-scale survey was mounted for biological control organisms. During these surveys, we found Casmara subagronoma, a stem-boring moth in Hong Kong and began to test its host affinity to R. tomentosa. Casmara subagronoma is only known from two male specimens from Vietnam and Indonesia, so in addition to host range tests, we also describe the female and immature life stages in this manuscript. Casmara subagronoma completes its life cycle in nearly 18 months and requires large, whole plants to do so. While R. tomentosa is likely the preferred host, C. subagronoma also completed its development on Myrcianthes fragrans, a Florida native, and Myrtus communis. The knowledge gained about this genus and its biology are quite valuable, but C. subagronoma will not be pursued for a biological control agent due to its long life cycle, difficult rearing protocols, and potentially broad host range.Rhodomyrtus tomentosa is a perennial shrub native to Southeast Asia and is invasive in South Florida and Hawai’i, USA. During surveys of R. tomentosa in Hong Kong from 2013–2018 for potential biological control agents, we collected larvae of the stem borer, Casmara subagronoma. Larvae were shipped in stems to a USDA-ARS quarantine facility where they were reared and subjected to biology studies and preliminary host range examinations. Casmara subagronoma is the most recent Casmara species to be described from males collected in Vietnam and Indonesia. Because the original species description was based on only two male specimens, we also provide a detailed description of the female, egg, larva, and pupa. Finally, we conducted preliminary host range trials utilizing Myrtus communis, Myrcianthes fragrans, and Camellia sinensis. Casmara subagronoma emerged from M. fragrans, a Florida-native shrub, and larvae were able to survive in non-target stems for over a year (>400 days). Based on these findings and difficulty in rearing, we do not believe C. subagronoma is a suitable insect for biological control of R. tomentosa at this time, but may warrant further study. This investigation also illustrates the importance of host surveys for conservation and taxonomic purposes.