Use of glufosinate-ammonium to control cruciferous weed species in glufosinate-resistant winter oilseed rape

Weed control is an important component of integrated cropping systems. However, cruciferous weeds are difficult to control in conventional winter oilseed rape (Brassica napus L.) and new herbicide options are needed. The aim of this study was to determine the potential for use of glufosinate-ammonium (2-amino-4-(hydroxymethyl-phosphinyl)-butanoic acid) as a flexible post-emergence herbicide for control of cruciferous weeds in glufosinate-resistant winter oilseed rape in the Hercynian dry region of Central Germany. The effects of glufosinate-ammonium (900 g active ingredients ha(-1)) on chlorophyll fluorescence and dry matter in 4-week-old Sisymbrium loeselii L. (tall hedge mustard), S. officinale (L.) Scop. (hedge mustard), S. altissimum L. (tall tumble mustard), and Descurainia sophia (L.) Webb ex Prantl (flixweed) were assessed under controlled conditions in a growth room. A 2-year field trial was used to investigate the effect of glufosinate-ammonium on the dry matter of S. loeselii. Therefore, different application times (two- to four-leaf stage, five- to six-leaf stage, end of vegetative period in autumn, beginning of vegetative period in spring) and herbicide rates (450 and 900 g a.i. ha(-1)) were tested. Under controlled growth room conditions, plants of all four cruciferous weed species showed a gradual decrease in the quantum yield of photosystem II. The quantum yield was less than 20% of the control plants measured from 0 to 34 It after application. Dry matter production of all four species was reduced to less than 3% that of the untreated control 4 weeks after application. Under field conditions, dry matter production of S. loeselii varied in dependence on the environmental conditions and was 0-88% of the control plants. Under controlled and field conditions, the results indicate that glufosinate-ammonium is effective in post-emergence control of the tested cruciferous weeds in glufosinate-resistant winter oilseed rape. Under field conditions, weather and crop growth influenced herbicide effectiveness. (C) 2003 Elsevier B.V. All rights reserved.