Spring-applied saflufenacil and imazapic provided longer lasting Euphorbia esula L. control than fall applications

• Published in: Crop protection 2013-05, Vol.47, p.30-34
• Main Authors: Datta, Avishek, Rapp, Ryan E., Scott, Jon E., Charvat, Leo D., Zawierucha, Joseph, Knezevic, Stevan Z.
• Format: Article
• Language: English
• Subjects: broadleaf weeds; Dormancy; Dose–response curve; Euphorbia esula; Fall weed control; field crops; field experimentation; grasses; imazapic; Invasive weed control; Noxious weed; Pasture and rangeland weed; pastures; Perennial weed control; plant density; rangelands; spring; Spring weed control; weed control
• ISSN: 0261-2194; 1873-6904
• DOI: 10.1016/j.cropro.2012.12.006

Euphorbia esula is a serious weed problem in North American rangeland and pasture. Saflufenacil is a new herbicide being primarily developed for pre-plant and pre-emergence broadleaf weed control in several field crops. Imazapic is commonly used for E. esula control as a fall treatment, because spring applications do not provide satisfactory control and may cause grass injury. Field experiments were conducted during the spring and fall of 2007 and 2008 at O'Neill, Nebraska, USA with the objective to describe dose–response curves of saflufenacil and imazapic applied alone and tank-mixed in order to determine the best ratios of the two herbicides for E. esula control. The response of E. esula to saflufenacil for each imazapic treatment was evaluated in terms of plant density reduction over time, based upon DR90 (effective dose that provides 90% density reduction). In general, saflufenacil or imazapic applied alone did not provide satisfactory long-term E. esula control, regardless of application timings. Overall, E. esula control increased when saflufenacil was applied with imazapic, especially as the doses of both herbicides increased. In the spring study, a 90% density reduction of E. esula for 24 months after treatment (MAT) was achieved with saflufenacil at 127 g ha−1 tank-mixed with 105 g ha−1 of imazapic. When applied in the fall, a significantly higher saflufenacil dose (418 g ha−1) was needed in a tank-mix with 105 g ha−1 of imazapic to obtain 90% density reduction for up to 23 MAT. This result indicates that spring applications of imazapic plus saflufenacil provided better E. esula control than fall treatments. ► Saflufenacil-SAF or imazapic-IMI alone did not provide long-term Euphorbia esula control. ► E. esula control increased when SAF was applied with IMI. ► A 90% DR of E. esula in spring was achieved with 127 g ha−1 SAF and 105 g ha−1 IMI. ► A 90% DR of E. esula in fall was obtained with 418 g ha−1 SAF and 105 g ha−1 IMI. ► Spring applications of IMI plus SAF provided better E. esula control than fall.