Glufosinate at 1.1 and 2.2 kg/ha injured ‘Koshihikari’ rice lines that were transformed with the BAR gene from 0 to 53%. However, transgenic ‘Gulfmont’ rice was not injured. Rice yields of transgenic ‘Gulfmont’ lines and six of nine ‘Koshihikari’ lines were not affected by 2.2 kg/ha glufosinate. In field studies, flooding reduced the efficacy of glufosinate in controlling red rice, and greenhouse tests determined that glufosinate efficacy was reduced when red rice was submerged between 25 and 50% of its height. Plant heights and dry weights of red rice increased as flood water depth increased at all rates of glufosinate.

Glufosinate at 2.2 kg ai/ha injured rice transformed with the BAR gene more when applied to one- to two-leaf (23 to 26%) than to three- to four-leaf (13 to 19%) plants. Visible injury was least when applications were made at boot stage (3 to 14%). However, applications at boot stage caused an average grain yield reduction of 16%. Most treatments did not influence rice plant height. Among single applications (0.3, 0.4, 0.6, 0.8, and 1.1 kg/ha), 1.1 kg/ha glufosinate at three- to four-leaf stage of red rice resulted in greater control (91%) than at panicle initiation (74%) or at boot stage (77%). Injury to red rice was two to 11 times greater than the injury to BAR-transformed rice depending on glufosinate rate and application timing.

Field studies were conducted from 1996 to 1998 at Queenstown, MD to evaluate weed management programs utilizing single and multiple applications of glufosinate, with and without preemergence (PRE) and postemergence herbicides in both glufosinate-resistant (GR) corn and soybean. No herbicide treatment resulted in corn or soybean injury greater than 10% at 7 d after treatment (DAT). No injury was visible at 14 DAT for both GR corn and soybean. In corn, all treatments provided 72% or greater giant foxtail control 14 wk after planting (WAP). With soybean, in 1996 and 1998, few differences in giant foxtail control were observed, with all treatments providing at least 93% giant foxtail control 12 WAP. For common lambsquarters control in GR corn, there were no differences in control among treatments for 1996 and 1997. Over 80% common lambsquarters control was observed both years with all treatments 14 WAP. Glufosinate + atrazine at 0.4 kg/ha + 1.7 kg ai/ha, respectively, provided 100% season-long common lambsquarters control all three years of the study. For GR soybean, few differences in common lambsquarters control existed between treatments for all three years. Most treatments provided 72% or greater common lambsquarters control 12 WAP. Few differences in grain yield between herbicide treatments were observed for either GR corn or soybean. These studies illustrated that glufosinate, whether applied alone, sequentially, in tank-mixes, or as an overlay to a PRE program in GR corn and soybean is a viable herbicide program for the control of giant foxtail and common lambsquarters.