Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2000
Publication Date: N/A
Interpretive Summary: Redvine is a native perennial vine found extensively in cultivated fields, wastelands, fence rows, yards, riverbanks, and swamps and forests in the Mississippi Delta region. Redvine is difficult to control because it can propagate from a deeply positioned and extensive root system. Glyphosate, a nonselective, broad-spectrum, and environmentally benign herbicide has potential to control redvine. Although glyphosate is considered a nonselective herbicide, its ability to control weed is species dependent. Scientists at the Southern Weed Science Research Unit conducted greenhouse and growth chamber studies to examine glyphosate efficacy, rainfastness, absorption, and translocation in redvine. Redvine was not always controlled at normal use rates. A simulated rainfall within 24 hours after herbicide application resulted in loss of one-fourth activity of glyphosate in redvine. Absorption studies indicated that although absorption was rapid with considerable amounts absorbed, these amounts were not sufficient to provide rainfastness up to 48 hours after herbicide application in redvine. These results suggest that longer periods of plant exposure to the herbicide and high summer temperatures could increase glyphosate absorption and its translocation into rootstocks of redvine. However, effective control would still require above normal use rates.
Technical Abstract: Greenhouse and growth chamber experiments were conducted to study glyphosate efficacy, rainfastness, absorption, and translocation in redvine. Redvine control ranged from 55% at 0.56 kg/ha glyphosate to 98% at 4.48 kg/ha. Glyphosate applied above 1.12 kg/ha, greatly reduced regrowth from rootstocks attached to the treated plants. A simulated rainfall of 2.5 cm (7.5 cm/h intensity) within 24 h after herbicide application reduced glyphosate efficacy by one-fourth compared with no simulated rainfall. Absorption of 14**C-glyphosate in redvine increased from 1.8 to 21.9% and translocation increased from 0.1 to 8.1% from 6 to 192 h exposure, respectively. Translocation was both acropetal and basipetal, and by 96 h exposure, the radioactivity was widely distributed within the plant. Absorption and translocation was greatly affected by post-treatment temperature. Absorption and translocation were highest (34.9 and 10.6%, respectively) in plants maintained at 35/30 C (14/10 h, day/night), followed by 15/10 C (21.2 and 4.9%, respectively), and was lowest (7.8 and 1.6%, respectively) in plants maintained at 25/20 C. Results suggest that longer periods of leaf exposure to the herbicide and high summer temperatures could increase glyphosate absorption and its translocation into redvine rootstocks. Effective control of redvine, however, requires rates of glyphosate above 2.24 kg/ha.