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Title: ABSORPTION, TRANSLOCATION, AND ACTIVITY OF GLUFOSINATE IN FOUR WEED SPECIES

Author
item STECKEL, GREGORY - UNIV OF ILLINOIS
item HART, STEPHEN - UNIV OF ILLINOIS
item WAX, LOYD

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: We conducted greenhouse and laboratory studies to compare the uptake, movement, and activity of the herbicide glufosinate on four weed species common in midwest corn and soybean fields, giant foxtail, barnyardgrass, common lambsquarters, and velvetleaf. The sensitivity of these weeds to foliarly applied glufosinate was, in order of most sensitive to least sensitive, giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters. Radiolabelled herbicide was used to determine uptake and movement of the herbicide by these weed species. We found that absorption and translocation of the herbicide correlated well with sensitivity of the species. That is, the most sensitive species absorbed and translocated much more of the herbicide within 24 hours after treatment than did the least sensitive weed species. Differences in absorption and translocation of the radiolabelled herbicide appears to explain the differences in ability of this herbicide to control these four weed species. These findings help to explain how this herbicide controls some species better than others, and should provide helpful information about the optimum use of this herbicide. These results should be beneficial to public and private weed scientists who are developing improved weed management programs for corn and soybeans.

Technical Abstract: Greenhouse and laboratory experiments were conducted to evaluate the efficacy, foliar absorption, and translocation of glufosinate on barnyardgrass, giant foxtail, common lambsquarters, and velvetleaf. The rate of glufosinate required to reduce shoot dry weight by 50% (GR50) varied by weed species. GR50 data indicated that giant foxtail was the most sensitive to glufosinate, followed by barnyardgrass, then velvetleaf, and common lambsquarters was found to be the most tolerant species. GR50 values for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters were 69, 186, 199, and 235 g ai ha-1 respectively. Absorption and translocation of glufosinate correlated with sensitivity at the whole plant level. Absorption of 14C-glufosinate increased with time and reached nearly maximum 24 hours after treatment (HAT). Absorption of 14C-glufosinate was 67, 53, 42, 16% for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters respectively. Translocation of absorbed 14C-glufosinate from the treated leaf was the greatest for giant foxtail and barnyardgrass and was 15 and 14% 24 HAT of absorbed 14C-glufosinate, respectively. This compared to 5 and <1% for translocation of absorbed 14C-glufosinate translocated by giant foxtail and barnyardgrass was found in the below related leaf area and roots of the plant, indicated phloem mobility of the herbicide. Translocation in velvetleaf was more evenly distributed between the above and below treated leaf. Little translocation of glufosinate from the treated leaf of common lambsquarters was detected into either the above or below treated leaf portion of the plant.