ARS | Publication request: Postemergence Herbicide Treatment Effectiveness for Lesquerella

Submitted to: Proceedings Assoc for Advancement of Industrial Crops (AAIC) Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: August 15, 2005
Publication Date: September 21, 2005
Citation: Foster, M.A., Dierig, D.A., Wintermeyer, M. 2005. Postemergence herbicide treatment effectiveness for lesquerella. pp 699-700. In M.J. Pascual-Villalobos, F.S. Nakayama, C.A, Bailey, E. Correal and W.W. Schloman, Jr. (ed.) Industrial Crops and Rural Development. Proceedings Assoc for Advancement of Industrial Crops (AAIC) Annual Meeting, Murcia, Spain, 17-21 September 2005.

Technical Abstract: Weed control is critical for establishing lesquerella. Lesquerella seedlings grow slowly after emergence, and offer little competition with broadleaf weeds. Several herbicides are registered under Special Local Needs (24c) in Arizona and Texas for control of annual broadleaf weeds: trifluralin provides adequate preemergence weed control, fluazifop controls grasses postemergence, and oxyfluorfen is used for postemergence control of annual broadleaf weeds. Alternative postemergence treatments for broadleaf weed control that have a broader spectrum of control, and are more cost effective than oxyfluorfen must be investigated. The objective of this research was to examine the tolerance of lesquerella to six herbicides labeled for use in other field crops. Our study was initiated October 13, 2004 at The University of Arizona Maricopa Agricultural Center. Advanced generation lesquerella seed was planted on level basins with a Brillion Seeder at 11 kg/ha, and flood irrigated. Herbicide treatments consisted of plots (8 m long and 2.5 m wide) arranged in a randomized complete block design with four replications. The following postemergence herbicides were applied November 23, 2004 when the lesquerella seedlings were in the 8-10 true leaf stage: clopyralid (0.3, 0.6, 1.1 kg ai/ha), ethametsulfuron (15, 20, 30 g ai/ha), imazamox (35, 45,56 g ai/ha), oxyfluorfen ( 0.3, 0.6, 1.1 kg ai/ha), thifensulfuron (15, 20, 30 g ai/ha), and thifensulfuron+tribenuron (15, 20, 30 g ai/ha). Treatments were applied using a CO2-powered backpack sprayer with a three-nozzle boom (Teejet 8003 flat fan nozzles) delivering 225 L/ha at 187 kPa. Lesquerella stand density was determined in each plot by counting the seedlings in a 0.25 m2 quadrat. Ten lesquerella seedlings in the 2 to 4 leaf stage were marked in each plot to monitor the effect of the herbicides on this growth stage. Overall lesquerella injury and weed control were estimated visually from 0 to 100% with 0 = no visible effect and 100 = complete crop death or weed control. Ratings were made weekly for 60 days by comparing each treatment to the untreated control within the same replication. Plant biomass and seed production were determined in June 2005 by harvesting an 8 m by 2 m strip in each treatment with a Hege 180 combine. Seed oil production and oil content was determined at the USDA-ARS U.S. Water Conservation Lab in Phoenix, AZ. Results from this study will identify postemergence herbicides that may be safe for use in lesquerella production.