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

Deschampsia flexuosa is a commonly occurring calcifuge grasswhich can be detrimental to tree regeneration. In the work reportedhere, two experiments using pot-grown plants and one field experimentwere set up to investigate the relative efficacy of variousherbicides in controlling D. flexuosa. Cycloxydim, glyphosateand imazapyr applied in the summer killed virtually all pot-grownplants of D. flexuosa within 1 year of treatment. Hexazinoneand propyzamide were also effective at the recommended doses.Mixture B enhanced the efficacy of several herbicide treatmentsbut pre-spraying plant moisture stress had no effect on subsequentherbicide activity. Cycloxydim and imazapyr applied in springor summer gave excellent long-term control in the field. Itis concluded that if non-chemical approaches such as canopymanipulation or cultivation fail to give adequate control ofD. flexuosa and herbicide use becomes necessary to allow treeregeneration, then cycloxydim applied at 0.45 kg a.i. ha^–1appears to be an effective alternative to the use of more broad-spectrumproducts, and gives very good tree tolerance. If herbicide useis required prior to tree establishment, glyphosate may be acheaper option and will control a broader spectrum of weeds,although it is slightly less effective than cycloxydim on D.flexuosa.