Greenhouse and laboratory experiments were conducted to evaluate foliar absorption, translocation, and efficacy of glufosinate on four weed species. The rate of glufosinate required to reduce shoot dry weight by 50% (GR50) varied between weed species. GR50 values for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters were 69, 186, 199, and 235 g ai ha−1, respectively. Absorption of 14C-glufosinate increased with time and reached a plateau 24 hours after treatment (HAT). Absorption of 14C-glufosinate was 67, 53, 42, and 16% for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters, respectively. Translocation of absorbed 14C-glufosinate from the treated leaf was greatest for giant foxtail and barnyardgrass (15 and 14% 24 HAT of absorbed 14C-glufosinate, respectively). This compared to 5 and < 1% for translocation of absorbed 14C-glufosinate from the treated leaves of velvetleaf and common lambsquarters. The majority of 14C-glufosinate translocated by giant foxtail and barnyardgrass was found below the treated leaf and in the roots, indicating phloem mobility of the herbicide. Differential absorption and translocation of 14C-glufosinate may be contributing factors to the differential sensitivity observed between weed species.

Field studies were conducted in 1990 and 1991 to evaluate johnsongrass control and interference in corn using combinations of nicosulfuron, EPTC + dichlormid, and cultivation. Nicosulfuron applied to 30-cm-tall rhizome johnsongrass provided greater control and corn yield than a later application to 60-cm-tall johnsongrass. Johnsongrass control and corn yield within the later nicosulfuron treatment were improved by a preplant application of EPTC. EPTC and/or cultivation alone provided less johnsongrass control and lower corn yield than nicosulfuron or handweeding.

Field experiments were conducted in 1993, 1994, and 1995 to determine the effects of glufosinate rate and application timing on giant foxtail, common lambsquarters, common cocklebur, and Pennsylvania smartweed control in absence of a crop. Glufosinate at 140 g ai/ha controlled less than 80% of the weed species evaluated. When glufosinate rate was increased to 420 g/ha and applied to 10-cm giant foxtail, control was greater than 80% all 3 yr of the study. Applications made to 10-cm plants resulted in 80% or greater control for common cocklebur all 3 yr and Pennsylvania smartweed 2 of the 3 yr with 420 and 560 g/ha, respectively. Common lambsquarters was the most tolerant species evaluated and was not consistently controlled acceptably (> 80%), even with glufosinate at rates of 560 g/ha. Control with glufosinate at 420 or 560 g/ha was most effective when applied at the 10-cm weed height compared either to the 5- or 15-cm weed height.