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Title: Racer efficacy study – Lane, Fall 2007

Author
item Webber Iii, Charles
item SHREFLER, JAMES - OSU, LANE, OK
item BRANDENBERGER, LYNN - OSU, STILLWATER, OK
item WELLS, LYNDA - OSU, STILLWATER, OK

Submitted to: Extension Publications
Publication Type: Other
Publication Acceptance Date: 2/5/2008
Publication Date: 4/1/2008
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P., Wells, L.K. 2008. Racer efficacy study – Lane, Fall 2007. In: Brandenberger, L., Wells, L., editors. 2007 Vegetable Weed Control Report. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture and Landscape Architecture. Stillwater, OK. MP-162. p. 11-14.

Interpretive Summary: Organic producers have identified weed control as their highest research priority. Racer (ammonium nonanoate) is a potential organic herbicide that could help producers control yield reducing weeds and the large labor demands required with hand weed removal. Racer is labeled for non-food use and efforts are currently underway to label it as a bio-herbicide for organically grown food crops. The main component of Racer is ammonium nonanoate which occurs in nature and is primarily formed from biodegradation of higher fatty acids. The objective of this study was to investigate different nozzles, rates of active ingredients, and overall rates of spray material for control of endemic weed populations. The study was conducted at the Lane Agriculture Center at Lane, Oklahoma. Treatments included two nozzle types (TeeJet XR8003 and TeeJet XR8005) operated at recommended nozzle pressures, three application concentrations of Racer (8.0, 11.2, and 14.4 lbs ai/a), and two application volumes (35 and 70 gpa) for a total of 12 treatments. Plots were rated on 9/19/07, 9/22/07, and 9/25/07 for percent control of tumble pigweed (Amaranthus albus L.) and goosegrass (Eleusine indica L. Gaertn.). Carpetweed (Mollugo verticillat L.) was evaluated at the first two evaluation dates and cutleaf evening primrose was evaluated at the final evaluation date. In general, herbicidal activity on weed populations present in the study was observed as burning and necrosis of plant tissues present at application. This is typical for contact herbicides that function as "burn-down" materials. Depending on weed species, plants not completely killed began to recover during the seven day period that plots were rated. In general, weed control increased with increased herbicide rate. This was true for all weed species in the study except for cutleaf evening primrose, where control was never greater than 25%. More treatments with 8005 nozzle had higher levels of control than with the 8003 nozzle treatments. Tumble pigweed control from Racer was up to 90%, and generally no lower than 80% with the highest rates at the earliest two evaluations. At the third evaluation, ratings were generally below 80%. Exceptions were the combination of the highest application rates and pressures. Racer control of carpetweed was high with several treatments providing 90%+ control of this weed on 9/19/07 and control generally remained as great at the 9/22 rating. Rating at 9/25 was not possible due to grass present in some plots. Goosegrass control was as high as 80% on 9/19/07. Significant decreases in control were found for the intermediate rate compared to the high rate. On 9/25/07 control was no greater than 50%. There were no significant changes in number of live weeds for any of the evaluation dates. Racer provided partial to substantial control of three of the weed species evaluated. Only minimal control of cutleaf evening primrose was observed. There were general tendencies of increased control with increased herbicide rate. Based upon the results, the authors recommend further study to determine if similar results would be observed during a different season with different conditions, but would recommend examining rates of 11.2 and 14.4 lbs ai/acre and possibly greater rates.

Technical Abstract: Racer (ammonium nonanoate) is labeled for non-food use and efforts are currently underway to label it as a bio-herbicide for organically grown food crops. The main component of Racer is ammonium nonanoate which occurs in nature and is primarily formed from biodegradation of higher fatty acids. The objective of this study was to investigate different nozzles, rates of active ingredients, and overall rates of spray material for control of endemic weed populations. The study was conducted at the Lane Agriculture Center at Lane, Oklahoma. Treatments included two nozzle types (TeeJet XR8003 and TeeJet XR8005) operated at recommended nozzle pressures, three application concentrations of Racer (8.0, 11.2, and 14.4 lbs ai/a), and two application volumes (35 and 70 gpa) for a total of 12 treatments. Plots were rated on 9/19/07, 9/22/07, and 9/25/07 for percent control of tumble pigweed (Amaranthus albus L.) and goosegrass (Eleusine indica L. Gaertn.). Carpetweed (Mollugo verticillat L.) was evaluated at the first two evaluation dates and cutleaf evening primrose was evaluated at the final evaluation date. In general, herbicidal activity on weed populations present in the study was observed as burning and necrosis of plant tissues present at application. This is typical for contact herbicides that function as "burn-down" materials. Depending on weed species, plants not completely killed began to recover during the seven day period that plots were rated. In general, weed control increased with increased herbicide rate. This was true for all weed species in the study except for cutleaf evening primrose, where control was never greater than 25%. More treatments with 8005 nozzle had higher levels of control than with the 8003 nozzle treatments. Tumble pigweed control from Racer was up to 90%, and generally no lower than 80% with the highest rates at the earliest two evaluations. At the third evaluation, ratings were generally below 80%. Exceptions were the combination of the highest application rates and pressures. Racer control of carpetweed was high with several treatments providing 90%+ control of this weed on 9/19/07 and control generally remained as great at the 9/22 rating. Rating at 9/25 was not possible due to grass present in some plots. Goosegrass control was as high as 80% on 9/19/07. Significant decreases in control were found for the intermediate rate compared to the high rate. On 9/25/07 control was no greater than 50%. There were no significant changes in number of live weeds for any of the evaluation dates. Racer provided partial to substantial control of three of the weed species evaluated. Only minimal control of cutleaf evening primrose was observed. There were general tendencies of increased control with increased herbicide rate. Based upon the results, the authors recommend further study to determine if similar results would be observed during a different season with different conditions, but would recommend examining rates of 11.2 and 14.4 lbs ai/acre and possibly greater rates.