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United States Department of Agriculture

Agricultural Research Service

Title: Transplanted onion weed control Calvin, Oklahoma 2002

Authors
item Shrefler, J.W. - OSU - LANE, OK
item Webber, Charles

Submitted to: Oklahoma Agriculture Experiment Station Departmental Publication
Publication Type: Experiment Station
Publication Acceptance Date: January 22, 2004
Publication Date: February 2, 2004
Citation: Shrefler, J., Webber III, C.L. 2004. Transplanted onion weed control Calvin, Oklahoma 2002. In: Brandenberger, L., Wells, L., editors. 2003 Vegetable Weed Control Studies. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture and Landscape Architecture. Stillwater, OK. MP-162. p. 11-13.

Interpretive Summary: Fresh market onion production is increasing in Arkansas, Oklahoma, and north Texas. Although mechanical weed control can successfully control weeds between rows, producers need reliable methods for controlling the weeds within the crop row between the onions. Field research was conducted in southeast Oklahoma (Calvin, OK) to determine the influence of eighteen weed control treatments on onion yield, crop safety, and weed control efficacy. Commercial produced onion transplants, cv. 'Candy,' were established in the field on March 29 in single rows on 20 inch wide raised beds on 30 inch centers with 6 inches between onion transplants. Treatments included herbicides applied preemergence to weeds on April 5, postemergence to weeds on May 20, or applied on both dates. Herbicides applied included three synthetic herbicides (pendimethalin, oxyfluorfen, and dimethenamid), and an organic herbicide (corn gluten meal). Total onion yields ranged from 10,382 lb/a (weedy-check) to 14,095 lb/a (oxyfluorfen, 0.25 lb/a, and pendimethalin, 0.4125 lb/a, applied on April 5). Whenever dimethenamid was applied at 0.75 lb/a or 1.5 lb/a with either pendimethalin or oxyfluorfen, yellow nutsedge (Cypertus esculentus L.) control increased, resulting in 71 to 97% control. Toothed spurge (Euphorbia dentate Michx.) was bested controlled by either dimethenamid at 1.5 lb/a applied on April 5 with oxyfluorfen at 0.5 lb/ac applied on May 20 (87% toothed spurge control) or pendimethalin at 0.4125 lb/a and dimethenamid at 0.75 lb/a applied on April 5 with oxyfluorfen 0.5 lb/a on May 20 (80% toothed spurge control). Good to excellent Palmer amaranth (Amaranthus palmer S.), 86 to 99% control, and annual grasses, 89 to 99% control, was achieved with herbicides treatments that contained either rate of dimethenamid (0.75 lb/a or 1.5 lb/a) with either oxyfluorfen (0.5 lb/a) or pendimethalin (0.4125 lb/a). Single applications of the individual herbicides of either oxyfluorfen at 0.5 lb/a or pendimethalin at 0.825 lb/a at the first application date, April 5, also provide good to excellent control (89 to 99% control of Palmer amaranthus or annual grasses). Corn gluten meal applications at 2670 lb/a provide some weed control yellow nutsedge (45%), toothed spurge (47%), Palmer amaranth (67%), and annual grasses (67%). The research determined the weed control and yield advantages of various herbicides used individually, in split applications, or in combination with other herbicides. In addition, dimethenamid (0.75 lb/a or 1.5 lb/a) applied in combination with oxyfluorfen at 0.5 lb/a increase yellow nutsedge above the level of oxyfluorfen and pendimethalin applied individually or in combination.

Technical Abstract: Interest in fresh market onion production is increasing in Arkansas, Oklahoma, and north Texas. Effective weed control is essential in sweet onion production because even a small amount of weed competition can result in large reductions in onion yields and quality. Field research was conducted in southeast Oklahoma (Calvin, OK) to determine the influence of eighteen weed control treatments on onion yield, crop safety, and weed control efficacy. Commercial produced onion transplants, cv. 'Candy,' were established in the field on March 29 in single rows on 20 inch wide raised beds on 30 inch centers with 6 inches between onion transplants. Treatments included herbicides applied preemergence to weeds on April 5, postemergence to weeds on May 20, or applied on both dates. Herbicides applied included three synthetic herbicides (pendimethalin, oxyfluorfen, and dimethenamid), and an organic herbicide (corn gluten meal). Total onion yields ranged from 10,382 lb/a (weedy-check) to 14,095 lb/a (oxyfluorfen, 0.25 lb/a, and pendimethalin, 0.4125 lb/a, applied on April 5). Whenever dimethenamid was applied at 0.75 lb/a or 1.5 lb/a with either pendimethalin or oxyfluorfen, yellow nutsedge (Cypertus esculentus L.) control increased, resulting in 71 to 97% control. Toothed spurge (Euphorbia dentate Michx.) was bested controlled by either dimethenamid at 1.5 lb/a applied on April 5 with oxyfluorfen at 0.5 lb/ac applied on May 20 (87% toothed spurge control) or pendimethalin at 0.4125 lb/a and dimethenamid at 0.75 lb/a applied on April 5 with oxyfluorfen 0.5 lb/a on May 20 (80% toothed spurge control). Good to excellent Palmer amaranth (Amaranthus palmer S.), 86 to 99% control, and annual grasses, 89 to 99% control, was achieved with herbicides treatments that contained either rate of dimethenamid (0.75 lb/a or 1.5 lb/a) with either oxyfluorfen (0.5 lb/a) or pendimethalin (0.4125 lb/a). Single applications of the individual herbicides of either oxyfluorfen at 0.5 lb/a or pendimethalin at 0.825 lb/a at the first application date, April 5, also provide good to excellent control (89 to 99% control of Palmer amaranthus or annual grasses). Corn gluten meal applications at 2670 lb/a provide some weed control yellow nutsedge (45%), toothed spurge (47%), Palmer amaranth (67%), and annual grasses (67%). The research determined the weed control and yield advantages of various herbicides used individually, in split applications, or in combination with other herbicides. In addition, dimethenamid (0.75 lb/a or 1.5 lb/a) applied in combination with oxyfluorfen at 0.5 lb/a increase yellow nutsedge above the level of oxyfluorfen and pendimethalin applied individually or in combination.

Last Modified: 4/20/2014
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