This paper presents a survey of grass weeds in grass seed crops in Denmark. The survey is based on an analysis of data from a database containing monitoring of grass weeds in the period from 2004 to 2009 on an acreage of approximately 400,000 ha. The survey is based on weed monitoring carried out during a mandatory field inspection of grass seed crops. All fields grown with grasses for seed production are monitored shortly before harvest at a time when the weeds present are a result of a combination of the cropping history of the field, competition from the crop and the weed control carried out in the field. The survey showed that Poa annua, Elytrigia repens and Poa trivialis were the three most frequent grass weeds in grass seed crops. Furthermore, Bromus hordeaceus, Bromus sterilis, P. trivialis and Vulpia spp. showed an increasing frequency in the study period. The perennial weed, E. repens, and Dactylis glomerata were the only important grass weeds with a declining frequency during the six years. Vulpia spp. has recently become a significant problem in red fescue for seed production, and a significant increased frequency was seen during the study period. However, the study also showed that Vulpia spp. is primarily a problem in red fescue crops established in the autumn, whereas spring establishment of red fescue almost solves the problem with this primarily autumn-germinating grass weed.
Acta Agriculturae Scandinavica, Section B - Soil and Plant Science, 2013, Vol 63, Issue 7, p. 604-611