Seed germination ecology of creeping mannagrass (Glyceria acutiflora) and response to POST herbicides

Creeping mannagrass is a perennial grass weed widely distributed in China and is becoming increasingly problematic in nurseries and landscapes in some regions. Understanding the germination ecology and response to commonly available POST herbicides of this weed is critical to determining its adaptive capabilities and potential for infestation, and assist in the development of effective control strategies. In the light/dark regime, creeping mannagrass germinated over a wide range of temperatures (15/5 to 30/20 degrees C), with maximum germination at 20/10 degrees C (95%). No seed germinated at 35/25 or 10/0 degrees C. The time required for 50% of maximum germination increased as temperature decreased. Compared with the light/dark conditions, germination was slightly stimulated when seeds were placed in the dark. Creeping mannagrass is moderately tolerant to osmotic and salt stress, which had 53 and 50% germination rates at -0.6 mPa osmotic potential and 200 mM NaCl concentration, respectively. Seedling emergence of the seeds buried at a depth of 0.5 cm (86%) was higher than those sowing on the soil surface (17%), but declined with burial depth increasing. There were no differences in the emergence rates from a burial depth 0.5-2 cm. Few seeds (4%) could emerge when seeds were sowed at a depth of 8 cm. POST application of haloxyfop-R-methyl, quizalofop-p-ethyl, sethoxydim, and pinoxaden provides 100% control of creeping mannagrass at the three-leaf to five-leaf stages. To achieve 80% control with clodinafop-propargyl, mesosulfuron-methyl, and fenoxaprop-p-ethyl, herbicides had to be applied at the three-leaf stage.