Development and control of Sisymbrium loeselii L. in glufosinate-tolerant winter rapeseed

Sisymbrium and Descurainia species are one of the new problem weeds in wint er rapeseeed cropping. Their occurence was observed on rapeseed fields in S outhern Sachsen-Anhalt. S. loeselii was the predominant species. In a two-year field trial with glufosinate-tolerant rapeseed hybrids plant growth of S. loeselii and winter rapeseed was compared and interspecific co mpetitive effects were determined. Using different plant densities the comp etitiveness of rapeseed crop was varied. S. loeselii was sown in the plots, it reached a density up to 250 plants/m(2). Rapeseed plants have been very fast biomass producer whereas S. loeselii sh owed a slow initial growth. In general, the competitivness of rapeseed crop had a strong influence on the development of S. loeselii. The effect of S. loeselii on rapeseed yield was insignificant. Difficulties in harvesting a nd an increased corn moisture of rapeseed were observed as harmful effects of S. loeselii. In both years a flexible post-emergence control of S. loeselii in the herbi cide-tolerant rapeseed field was achieved by Liberty (Glufosinate). Referri ng to an integrated plant protection, this flexible control represent an ad vantage over the present used pre-emergence herbicides. The herbicidal effi cacy of Liberty, however, depended on environmental factors during applicat ion period.