Action: Control bracken
- One systematic review found that the herbicide asulam reduced bracken abundance if applied repeatedly, but cutting may be equally effective.
- A replicated laboratory trial in the UK found that the herbicide asulam inhibited the growth of three common moss species that commonly grow in association with bracken, when exposed over three weeks, but not if only exposed for 24 hours.
Bracken Pteridium aquilinum is native to the UK, but in many areas it is considered invasive. It has commonly been controlled by application of the herbicide asulam, or by cutting, although other techniques are sometimes used.
Supporting evidence from individual studies
A laboratory study in the UK (Rowntree et al. 2005) found that growth and development of three moss species were significantly inhibited by continuous exposure to the herbicide asulam over three weeks, but not by 24-hour exposure. The three moss species are widely distributed in the UK and frequently grow in association with bracken Pteridium aquilinum, so they are likely to be exposed when bracken is controlled using asulam. Campylopus introflexus was the least sensitive species tested and Polytrichum formosum the most sensitive, with a 10-fold difference in sensitivity between the two. The sensitivity of Bryum rubens lay between the two but was closer to that of C. introflexus than P. formosum. Mosses were exposed in sterile cultures to low concentrations (0.001-1 g/l) of the herbicide asulam for 24 hours or continuously, and their growth measured over three weeks.
A systematic review of methods to control bracken (Stewart et al. 2005) found that the herbicide asulam reduces bracken abundance but regeneration can be rapid and multiple applications are necessary. Complete eradication has not been demonstrated. Available evidence suggests cutting may be as effective as asulam application, particularly if there are two cuts in the same growing season. Further research is needed to compare the effectiveness of different ways of applying asulam and to compare cutting and asulam. There was not robust experimental evidence on the effectiveness of rolling, burning or grazing to control bracken. The review examined the effectiveness of using the herbicide asulam, cutting, hand-pulling, rolling, livestock grazing and burning to control bracken.
- Rowntree J.K., Sheffield E. & Burch J. (2005) Growth and development of mosses are inhibited by the common herbicide asulam. Bryologist, 108, 287-294
- Stewart G.B., Tyler C. & Pullin A.S. (2005) Effectiveness of current methods for the control of bracken (Pteridium aquilinum). Systematic Review No. 3. Centre for Evidence-Based Conservation