How long do bracken (Pteridium aquilinum (L.) Kuhn) control treatments maintain effectiveness?

Pteridium aquilinum is a problematic, perennial, invasive species worldwide that poses serious problems in the British uplands. However, there lack of knowledge on long-term success terms weed control and land improvement. We assessed effects six P. aquilinum-control treatments at two acid-grassland sites Scottish Borders (Sourhope 1 & 2). There were treatments: (i) untreated, (ii) cutting once-yearly, (iii) twice-yearly, (iv) asulam sprayed year 1, (v) once 1/asulam 2, (vi) 1/cut 2. The annual stopped after 9/10 years. measured response three variables over 25/26-years assessing aquilinum-performance, agricultural-improvement richness. estimated treatment “effect window”, defined as period which had significant effect relative to untreated experimental-controls. Results completely different for all experiments. At Sourhope much longer windows” than herbicide-based reducing performance, especially cut twice-yearly with 25-year window. differences reduced best (cut twice yearly) producing 13-year both experiments, asulam-based produce minimum window” 10 Increases index richness also obtained sites. “Effect (TVI) showed some improvement; 12–20 9–20 years TVI, 7–17 2–10 2 respectively. Species declined though time Cutting, preferably per year, was most effective but costliest, cost-effective approach being single spray. length suggest repeat-spraying every 10-years needed. Unfortunately, where aim recover biodiversity interventionist techniques such seeding will be use estimating impact perennial novel may other situations.