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Bryophytes suffer co-lateral damage in bracken battle
How selective are selective herbicides? Is it possible to control a nuisance species without damaging other plants? In relation to the control of bracken (Pteridium aquilinum) the answer appears to be ?No?, as described by Rowntree et al. (Manchester University and Natural History Museum, London, pp. 547-556). Bracken is a very invasive fern and in many parts of the world it is controlled with methyl (4-aminophenyl sulfonyl) carbamate. The soluble, commercially available version of this is known as Asulox, solutions of which are sprayed from the air or from the ground. Although bracken is the target species, other pteridophytes are also sensitive. The authors of this paper have now looked at the effects of Asulox on another important group of plants, the bryophytes. As a group they are very widespread and are key players in many ecosystems; several species occur with bracken. Eighteen species of mosses, across the taxonomic range, from UK habitats ranging from aquatic to relatively dry were used in this study. Moss shoots were exposed to various concentrations of Asulox by immersion for 24 h and then grown for a further 3 weeks in the absence of herbicide. All species showed some sensitivity, as measured by effects on elongation growth, although the EC50 values (the concentration at which a 50 % inhibition of elongation occurred) were over a 70-fold range. The most tolerant species was an aquatic moss Warnstofia fluitans (indeed, its growth was actually stimulated at low Asulox concentrations), whilst damp-loving Sphagnum species were among the most sensitive. Obviously, total immersion is not the same as exposure by drift or drip but we note that the EC50 values observed here were all very much lower than the concentrations used to control bracken in the field. Thus the authors suggest ?that mosses are potentially sensitive to Asulox exposure under field conditions?.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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