Dr. Catherine Tarasoff

Catherine graduated from Thompson Rivers University in 1998, after which she attended Oregon State University and earned a PhD in Crop Sciences with an emphasis on Weed Science, and a minor in Rangeland Ecology in 2007. Dr. Tarasoff went on to become the Invasive Plant Ecologist at Michigan Technological University. She recently moved back to British Columbia and runs her own consulting company, as well as holding an adjunct position at Thompson Rivers University, in the Department of Natural Resource Sciences. She has been a Professional Agrologist for 17 years through the BC Institute of Agrology. Her primary interest revolves around ecosystem restoration, in particular incorporating principals of plant biology and community ecology to understand and control invasive plant species.

Title: Biocontrol Resistance in St. John’s Wort – Challenges of invasive species management in rangeland ecosystems


Evidence of biocontrol resistance in British Columbia complicates an already challenging management regime.  Within British Columbia, range tenures cover 34 million hectares (roughly 1/3 of BC).  Because of the vast area, and diversity of ecosystem types, land managers must utilize all tools of integrated pest management in an extensive rather than intensive invasive species management program.  Biocontrol is considered an effective management tool for a number of invasive species, including St. John’s wort.  However, in 2018, biocontrol resistance was discovered at an historical release location (Marsh Creek, release – 1952).  Evidence of biocontrol resistance included both biochemical and physical differences between susceptible and resistant plants.  Resistant plants have significantly higher levels of hyperforin reflected by a drastic reduction in defoliation.  Resistant plants are taller, have greater leaf gland density, and larger leaves than their susceptible counterparts within the population.  Evidence of emerging biocontrol resistance within British Columbia emphasizes the need for increased funding and resources towards the development of new biocontrol agents.

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