Garlic mustard (Alliaria petiolata) invasion has been considered a transformative force in changing forest plant communities. Consequently, land managers have for decades tried to reduce spread and control abundance of the species in temperate forests – with little long-term success. The species is now found across much on the northern US and southern Canada and continues to spread. A classical biological control program was initiated in the late 1990’s and host specificity screening of several European weevils is nearing completion. A petition for release of a root feeding species has been submitted to regulatory agencies. Hand in hand with the development of a biological control option, investigations into ecosystem impacts of garlic mustard have continued. While a number of studies point to negative impacts on microbial communities and native plants, other studies failed to show evidence for negative impacts on invertebrates, plants or amphibians. In fact the most recent evidence points to garlic mustard invasions as a symptom of earthworm invasions – thus garlic mustard appears to be a passenger rather than the driver of forest community change. Furthermore, deer herbivory maybe an underappreciated factor in facilitating the demise of native plants and the rise of garlic mustard and other forest invaders in North America.
We will review the evidence for effects of garlic mustard on native species and communities, provide an overview of the status of the biocontrol program development, and discuss the implications for forest plant community management.