| Tuber oatgrass (Arrhenatherum elatius (L.) Presl. var. bulbosum (Willd.) Spenn.) is a perennial grass that often becomes a weed problem in Western Oregon. Control efforts using glyphosate often give unsatisfactory results. The effects of several factors on development of tuber oatgrass were investigated. Long days and cool temperatures (16/8h, 20/10C day/night) were favorable conditions for shoot growth in this study. Temperature increases from 20/10C to 30/20C day/night hastened corm formation in plants growing under short days (8/16h day/night), but not in those growing under long days (16/8h day/night). Vernalization was not required for plants to produce flowers. Tuber oatgrass seeds were not dormant and had a high germination percentage. Seed germination was most rapid at 15C; increasing the temperature to 25C significantly reduced total germination. Initial germination was delayed at 8 and 25C. The total number of corms that sprouted was the same at 8, 15, 25, and alternating 20/30C at 16/8h. Corms at different stages of maturity sprouted at different times. Immature corms sprouted more slowly and the time required for total sprouting was longer than that of mature corms. This variation in corm maturity would reduce the effectiveness of a single herbicide application.;Growth and development of tuber oatgrass was investigated in plants growing in the field and in outdoor pots. Under the mild climate of the Willamette Valley, Oregon, shoot emergence occurred in early fall, followed by vegetative growth during the winter and spring. In the summer, above-ground portions of the plant stopped growing and senesced. The highest absolute growth rate of the plants occurred in early May, shortly before the onset of the reproductive stage. In early May, the growth rate of corms was higher than that of the shoot.;The efficacy of glyphosate on tuber oatgrass was investigated in greenhouse and growth chamber studies. Glyphosate at 1.2 and 2.5 kg ae/ha significantly reduced new corm formation and corm viability. A 24-h period between glyphosate application and removal of the shoots was sufficient to cause maximum reduction in regrowth. Glyphosate applied at the 6- to 7-leaf stage controlled all of the tuber oatgrass. The total amount of... |
