Examining best management practices to control the invasion of Potentilla recta within northern intermountain grasslands

Abstract

Sulphur cinquefoil (Potentilla recta L.) is an invasive plant of concern within grasslands in the intermountain region of the northwestern United States and southwestern Canada. The aim of this research was to identify strategies to control and contain the spread of P. recta within northern intermountain grasslands, with a focus on grasslands in southeastern British Columbia, Canada.

In a field study, P. recta response to targeted goat grazing conducted once versus twice annually, aminopyralid as a one-time herbicide treatment, and integrated targeted goat grazing and aminopyralid application were examined. Treatment effects on plant community composition were also assessed. Targeted grazing was implemented in 2019 and 2020 and aminopyralid (56 g ai ha-1) was applied once in 2019. Greenhouse studies were conducted to assess P. recta growth response in native grass, forb, and grass and forb communities, with and without fertilizer, and to examine the existing prevalence of P. recta and other species in the soil seed bank at varying soil depths (0-5 cm, 5-10 cm, 10-15 cm) of P. recta invaded grasslands.

Potentilla recta aboveground biomass and number of seed heads declined following targeted grazing, with no differences between grazing once and grazing twice. Potentilla recta biomass and seed heads were reduced in the aminopyralid only and targeted grazing plus aminopyralid treatments with no differences between these treatments, indicating both targeted goat grazing and aminopyralid application are possible management options. Increased grass cover was observed in targeted grazing and aminopyralid treatments, suggesting potential off-target effects. Changes in plant community in response to treatments and interactions between treatment, site, and seasonal and annual variations are possible and must be considered as each can influence treatment efficacy.

Potentilla recta growth response did not differ between the native plant communities in the greenhouse; however, P. recta above and belowground biomass declined as native plant aboveground biomass increased. In the seed bank, seven of the nine species identified were non-native. The establishment of a productive plant community following P. recta control may be an important strategy to mitigate P. recta reinvasion or secondary invasion by other invasive species from the seed bank.