2018 ASHS Annual Conference

Interest in organic vegetable gardening has increased among homeowners in recent years. A growing number of people are searching for alternatives to glyphosate for weed suppression and control for establishing and maintaining vegetable gardens. In this study, weed control treatments were evaluated as well as the number of follow-up treatment applications needed for garden plot establishment. This study was conducted twice and each study lasted 131 days during the summer growing season of 2016 and 2017 in Richmond, KY. Treatments included a control and two application periods (fall and spring) of glyphosate, vinegar [5% acetic acid (AA)], 20% horticulture grade vinegar (20% AA), and 30% horticulture grade vinegar (30% AA). Following the treatments, each plot was evaluated using a quality rating (1-9 scale, 1=100% of the plot is dead and 9=100% of the plot is alive with weeds). After the initial treatment applications, quality ratings of the 5%, 20%, and 30% AA declined quickly to a rating of one within three days while the glyphosate required seven days to reach a rating of one. Treatments were reapplied to subplots in the spring when a plot received a quality rating of five (approximately 50% of the plot had regrown with weeds). Glyphosate performed the best requiring 71 to 80.8 days to reach 50% regrowth with both a fall and spring application of glyphosate (average of 78 days) achieving better results than a spring application only (average of 73.8 days). Control plots had the least number of days to full regrowth after the spring treatment application with 96 (2016) and 79.7 (2017) days after treatment (DAT) compared with glyphosate which took more than 105 DAT for full regrowth in 2017 and did not fully regrow in 2016 within the 131 days of the study. Five (2016) and nine (2017) retreatment applications to subplots were required in the 5% AA plots while glyphosate only required one retreatment application each year. The 20% and 30% AA both required approximately three (2016) and four (2017) retreatments. In this study, glyphosate has shown to be the more effective weed control method for vegetable gardens. In cucurbit gardens with reduced soil exposure, both 20% and 30% AA are viable alternatives to glyphosate.