The relative efficacy of herbicides for the control of Deschampsia flexuosa (L.) Trin. in woodland establishment in the UK

Summary Deschampsia fl exuosa is a commonly occurring calcifuge grass which can be detrimental to tree regeneration. In the work reported here, two experiments using pot-grown plants and one fi eld experiment were set up to investigate the relative effi cacy of various herbicides in controlling D. fl exuosa. Cycloxydim, glyphosate and imazapyr applied in the summer killed virtually all pot-grown plants of D. fl exuosa within 1 year of treatment. Hexazinone and propyzamide were also effective at the recommended doses. Mixture B enhanced the effi cacy of several herbicide treatments but pre-spraying plant moisture stress had no effect on subsequent herbicide activity. Cycloxydim and imazapyr applied in spring or summer gave excellent long-term control in the fi eld. It is concluded that if non-chemical approaches such as canopy manipulation or cultivation fail to give adequate control of D. fl exuosa and herbicide use becomes necessary to allow tree regeneration, then cycloxydim applied at 0.45 kg a.i. ha appears to be an effective alternative to the use of more broad-spectrum products, and gives very good tree tolerance. If herbicide use is required prior to tree establishment, glyphosate may be a cheaper option and will control a broader spectrum of weeds, although it is slightly less effective than cycloxydim on D. fl exuosa.