LEAFY SPURGE (EUPHORBIA-ESULA) CONTROL WITH FALL-APPLIED IMAZAPYR, IMAZAQUIN, AND IMAZETHAPYR

Imazapyr, imazaquin, and imazethapyr were evaluated for control of lea fy spurge. Herbicides were applied at 70, 140, and 280 g ae/ha in Fall 1989, 1990, or 1991 on a sub-irrigated meadow near Ainsworth, NE and a tallgrass prairie near Columbus, NE. Imazapyr, imazaquin, imazethapy r at 280 g/ha controlled leafy spurge 58, 82 and 73%, respectively, 9 mo after treatment (MAT) at Ainsworth. Leafy spurge control averaged 4 9% 9 MAT at Columbus where 280 g/ha of the imidazolinone herbicides we re applied. Leafy spurge yields were reduced at Ainsworth by 29 and 78 % where the imidazolinones were applied at 140 and 280 g/ha. By 11 MAT , leafy spurge control on areas treated with 280 g/ha declined to less than 60% at Ainsworth and 10% at Columbus. Perennial forage grass yie lds at both sites were generally unaffected by imazaquin or imazethapy r, but imazapyr at 280 g/ha reduced yields by 69 and 44% at Ainsworth and Columbus, respectively. Imidazolinone herbicides applied in the fa ll partially controlled leafy spurge, but did not increase perennial f orage grass yields.