Optimizing the efficacy of Canada’s oldest weed biocontrol system under changing climates

St. John’s wort (Hypericum perforatum) is an invasive plant species that came under attention during the mid-1900s, becoming one of the first and most highly successful plant-insect weed biocontrol systems in Canada, co-developed by Agriculture and Agri-Food Canada and the BC Ministry of Forests. Now, almost 70 years after the release of the first biocontrol agents, select populations of St. John’s wort in Western North America are at high density and invaded areas, while the majority of populations remain under successful biological control. Our project aims to identify ecological and environmental factors that may be driving the success of St. John’s wort in high-density patches as compared to patches under long-term successful biocontrol. We will focus on investigations of weed and biocontrol agent phenology, density, as well as plant chemistry, to better understand how bio-climatic factors impact both biocontrol agents and the target weed.