Absorption and translocation of glufosinate on four weed species

Abstract

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. GR50values for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters were 69, 186, 199, and 235 g ai ha−1, respectively. Absorption of14C-glufosinate increased with time and reached a plateau 24 hours after treatment (HAT). Absorption of14C-glufosinate was 67, 53, 42, and 16% for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters, respectively. Translocation of absorbed14C-glufosinate from the treated leaf was greatest for giant foxtail and barnyardgrass (15 and 14% 24 HAT of absorbed14C-glufosinate, respectively). This compared to 5 and < 1% for translocation of absorbed14C-glufosinate from the treated leaves of velvetleaf and common lambsquarters. The majority of14C-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 of14C-glufosinate may be contributing factors to the differential sensitivity observed between weed species.