The potential of the selective graminicides cycloxydim and propyzamide as habitat improvement tools for the pearl-bordered fritillary butterfly

The pearl-bordered fritillary (Boloria euphrosyne) is a resident UK butterfly which is in decline, partly because grasses can outcompete its preferred food plant, common dog-violet (Viola riviniana). We therefore investigated whether using graminicides could help to enhance the habitat quality of a violet-rich butterfly ride. Applications of 1.5 kg a.i. ha^-1 propyzamide or 0.45 kg a.i. ha^-1 cycloxydim both reduced grass cover and were associated with an increase in violet plants. Our work suggests that enhancing pearl-bordered fritillary habitat may not always be possible through herbicide use alone, but cycloxydim may have a useful role in helping to reduce competition from grasses.