EFFICACY OF BRACKEN (PTERIDIUM-AQUILINUM (L) KUHN) CONTROL TREATMENTSACROSS A RANGE OF CLIMATIC ZONES IN GREAT-BRITAIN - A NATIONAL OVERVIEW AND REGIONAL EXAMINATION OF TREATMENT EFFECTS

Bracken control field experiments were conducted at six locations acro ss Great Britain. The effects of various cutting and herbicide managem ent regimes upon the seasonal dynamics of bracken fronds and rhizomes were examined over a three year period. This enabled a national overvi ew towards bracken control to be constructed. Initially, spraying with asulam was the most effective treatment in reducing frond biomass and density but was least effective in reducing rhizome biomass. Differen tial reductions in rhizome biomass were observed in relation to cuttin g frequency, with cutting twice yearly giving superior control. The na tional trends confirmed a number of previous observations from indepen dent single-site studies; however, others were contradicted. Comparabl e management options were ranked consistently between the current and former investigation, however, the initial importance of differences i n cutting frequencies did not agree between studies. This multiple-sit e study improves understanding of the consequences of a national brack en control programme by reducing the influence of confounding site-spe cific factors, and recommendations for the most appropriate bracken co ntrol techniques are made. The extent to which individual sites reflec t a national trend in response to bracken control is considered and si tes are compared. The hierarchy of treatments identified at the nation al scale was found to apply generally within individual sites. However , several responses which proved significant at the countrywide level were not so clearly defined at the site scale. Cutting once yearly was the only management regime which appeared to give different bracken c ontrol between sites. All other treatments gave similar responses betw een sites. This result was found in the Scottish Borders, during the s econd year of control, when frond biomass and density (relative to unt reated plots) were greater than that recorded at other sites. This con trast was not found in subsequent monitoring. In terms of rhizome biom ass depletion, poorer control was achieved following cutting once year ly at the northern sites (Mull, Scottish Borders, Lake District) compa red with the southern sites (Clwyd, Breckland, Devon). The implication s of experimental results are discussed in relation to increased cost effectiveness of national bracken control programmes.