Abstract

Garlic mustard (Alliaria petiolata) is an invasive species threatening North American forest understories by outcompeting native plants and disrupting ecosystems. Classical biological control, introducing host-specific natural enemies from the plant’s native range, has emerged as a promising pest management strategy for controlling A. petiolata invasions. This study evaluated the European garlic mustard aphid (Lipaphis alliariae), a recently discovered aphid in North America, as a biological control agent to reduce A. petiolata populations. Through greenhouse and field experimentation, I evaluated aphid population dynamics and host-specificity on garlic mustard, as well as the effects of aphid influence on plant development, as measured by seed number, height, viability, and pod openness, and rosette height, dry weight, and stomatal conductance. Results showed that L. alliariae populations grew rapidly from one individual to over 647 within 28 days, which coincided with a significant decline in viable A. petiolata leaves. While the presence of aphids on plants did not impact seed number, plants with aphids produced seeds with 60% lower viability, reduced seed weight, and thicker, unopened pods relative to plants without aphids, indicating a potential negative impact on reproduction. Infestation of L. alliariae on A. petiolata rosettes reduced biomass (dry weight) by over 68%, decreased height by an average of 0.89 cm, and lowered stomatal conductance by 67%. Host-specificity trials confirmed L. alliariae’s preference for A. petiolata over other agricultural brassicas, showing minimal risk to economically important crops like broccoli and horseradish. These findings suggest that L. alliariae can reduce A. petiolata’s growth, reproduction, and competitiveness, supporting its potential as an effective and host-specific biocontrol agent. However, longer, more in-depth research into the seasonal phenology and host-specificity of L. alliariae is necessary before widespread field release is considered.

Advisor

Moreno, Carlo

Department

Environmental Studies

Disciplines

Forest Biology | Plant Sciences

Keywords

invasive plants, biological control, garlic mustard, aphids

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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© Copyright 2025 Kenzie Morris