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Title: Preemergence carfentrazone injury to vegetable and root crops

item Boydston, Rick

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2006
Publication Date: 8/1/2007
Citation: Boydston, R. A. Preemergence carfentrazone injury to vegetable and root crops. Proceedings of the Western Society of Weed Science 60:58. 2007.

Interpretive Summary:

Technical Abstract: Soil activity and persistence of carfentrazone-ethyl are generally believed to be limited. Several commercial onion fields in Washington and Oregon were damaged in 2005 where carfentrazone-ethyl was applied prior to onion emergence. Carfentrazone-ethyl applied preemergence at 0.032 lb ai/A damaged onion, sugar beet, carrot, broccoli, cabbage, and lettuce planted in sandy soil in greenhouse trials. Subsequent field studies were conducted in 2006 to measure the response of onion, carrot, sugar beets, peas, and snap beans to carfentrazone-ethyl applied at 0, 0.004, 0.008, 0.016, and 0.032 lb ai/A 5 to 7 days prior to planting, 1 day after planting, and 6 to 8 days after planting on a Warden sandy loam soil near Prosser, Washington. Carfentrazone-ethyl applied at all rates and timings did not reduce stand counts or yield of peas or snap beans compared to nontreated checks. Carrot stand was reduced by 25 and 53% and final yield was reduced 23 and 45% by carfentrazone-ethyl at 0.016 and 0.032 lb ai/A, respectively. Carrots were injured more by later preemergence applications than by treatments applied 5 days prior to planting. Onion and sugar beet stand counts were reduced by 28 and 42%, respectively, and final yields were reduced by 22 and 19%, respectively, by carfentrazone-ethyl at 0.032 lb ai/A. The timing of carfentrazone-ethyl application in relation to planting date had no effect on any onion or sugar beet parameters measured. In a trial conducted on a Quincy sand soil near Paterson, Washington, sugar beet stand and final yield were reduced by 50 and 47%, respectively by carfentrazone-ethyl at 0.016 lb ai/A when applied 1 day after planting. Based on these results, rates of carfentrazone-ethyl applied near the time of planting should not exceed 0.008 lb ai/A to carrots and should not exceed 0.016 lb ai/A to onion and sugar beets on sandy loam soils to avoid injury. Carfentrazone-ethyl should not exceed 0.008 lb ai/A to avoid injury to sugar beets on sandy soils.