Grant: Engage Grants Program

St. John's wort (Hypericum perforatum) is a perennial plant native to Europe that can reproduce and spread*aggressively, particularly in disturbed sites and rangelands. St. John's wort was first document in British*Columbia in 1947 and is an excellent competitor; it diminishes native plant species and can harm livestock in*the process. St. John's wort contains the chemicals hypericin and hyperforin in its leaves. Ingestion of hypericin*results in blisters, reduced reproductive performance, and in rare cases, death in livestock. Hyperforin has been*reported to serve as a defensive compound in response to herbivory.*The biocontrol beetle, Chrysolina hyperici, has historically been an effective biocontrol of St. John's wort. In*southern BC treatment by the beetle as reduced St. John's wort populations to less than 2% of pretreatment*levels. Unfortunately, observations indicate that St. John's wort is resurging on the landscape and the biocontrol*beetles are not performing as well as they have historically. Stressors, such as herbivory, are known to trigger*morphological and chemical predator defense mechanisms in plants, such as the production of toxins. St.*John's wort may have the ability to overproduce toxins hypericin and hyperforin as a predatory defense*mechanism in response to beetle herbivory.*To tackle the issue of resurging St. John's wort in BC, new methods are needed to control St. John's wort. Dow*has herbicides that have historically been effective at controlling St. John's wort. The use of this herbicide may*be needed if the population of St. John's wort has developed resistance to the biocontrol beetle. We will*determine if biocontrol resistance exists and the extent of resistance at 3 sites in BC. We will collaborate with*Corteva Agriscience to: 1) determine if biocontrol resistance is present within St. John's wort populations 2)*test the efficacy of different Corteva Agriscience herbicides on St John's wort populations; and 3) we will*present simple field based techniques for identifying potentially resistant plants and alternative weed control*options for St.John's wort control.