Semester of Graduation

Fall 2025

Degree

Master of Science (MS)

Department

Entomology

Document Type

Thesis

Abstract

Invasive woody plants have become dominant components of many forest understories in the southeastern United States. These species can displace native species, disrupt ecosystem processes, and reduce biodiversity. Chinese privet (Oleaceae: Ligustrum sinense Lour.) is an invasive shrub distributed through the Southeastern United States. The ligustrum weevil (Coleoptera: Curculionidae: Ochyromera ligustri Warner) is a non-native insect that was first found in the U.S. on Ligustrum in 1959. This weevil is considered a potential fortuitous biological control agent of invasive Ligustrum spp. in the U.S. The objectives of this study were to evaluate O. ligustri as a potential biological control agent of invasive Ligustrum through (1) cataloging the existing herbivore and pathogen pressure on U.S. Chinese privet, (2) describing the population dynamics of the O. ligustri in the U.S., and (3) evaluating the host-range of the O. ligustri.

I found that (1) Ligustrum sinense in the U.S. is fed upon by diverse generalist herbivores, and low pathogen pressure, (2) adults of the ligustrum weevil Ochyromera ligustri are present when their oviposition substrate, privet fruits, are available throughout the U.S., occupies a similar ecological niche, and is correlated with multiple environmental factors, and (3) based on adult host-range folivory tests, field collections, and fruit-morphology analysis, O. ligustri appears to be a generalist feeder but develops primarily within Ligustrum fruits. Together, these results suggest that O. ligustri has potential as a fortuitous seed-feeding agent for reducing privet reproduction and spread, but that adult feeding is relatively generalist and could produce minor cosmetic damage in ornamental settings. Before any management recommendations are made, further experiments are needed to confirm host specificity of oviposition and full larval development and to assess nursery/ornamental risk thresholds. If follow-up studies confirm narrow reproductive host range and measurable reductions in invasive privet recruitment, O. ligustri could be a promising biological control agent.

Date

11-24-2025

Committee Chair

Diaz, Rodrigo

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