Seed dormancy and germination phenology of grass weeds and implications for their control in cereals

Abstract

Seeds of Italian ryegrass, perennial ryegrass, wild oat, winter wild oat, phalaris and barnyard grass, collected during the 2005/06 season, were tested for dormancy and germination phenology between April and December 2006. In laboratory and outdoor environments, dormancy was widespread in grass weed but not in ryegrass seeds. The seeds of grass weeds had better germination in the outdoor environment than the laboratory. In the outdoor environment, only 15% of wild oat and winter wild oat, 19-63% of phalaris and 39% of barnyard grass seed germinated. Protracted germination varied between species in two to seven flushes. The earliest timing for effective post-emergence grass control under the experimental conditions appeared to be about 6 weeks after sowing for wild oats and ryegrasses, 12 weeks for phalaris and 14 weeks for barnyard grass. The extended germination periods of phalaris and barnyard grass are a challenge to growers in designing a cost-effective herbicide programme.