Herbicide Strategies for Managing Glyphosate- and Dicamba-Resistant Kochia in Roundup Ready 2 Xtend Soybean

Authors

V. Kumar, Kansas State UniversityFollow
R. Liu, Kansas State UniversityFollow
T. Lambert, Kansas State UniversityFollow
P. W. Stahlman, Kansas State Univ. Agric. Research Center–HaysFollow

Keywords

glyphosate, dicamba, multiple resistant kochia, dicamba-tolerant soybean

Abstract

Kochia populations with multiple resistance to glyphosate and dicamba are an increasing concern for growers in the High Plains region, including Kansas. A field study was conducted at the Kansas State University Agricultural Research Center near Hays, KS, to evaluate and develop herbicide options for controlling glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybean. The study site was uniformly infested with a glyphosate- and dicamba-resistant kochia population prior to soybean planting. Fifteen herbicide treatments (programs), including PRE alone and PRE followed by (fb) POST-applied herbicides, were investigated in a randomized complete block design with four replications. All PRE treatments included Roundup PowerMax for control of other weed species. Results indicated that a single PRE application of Spartan alone or with Engenia, Panther PRO, and Zidua plus Valor SX provided season-long control of glyphosate- and dicamba-resistant kochia. A single PRE application of Engenia or Zidua alone only provided 70 to 78% kochia control at 6 weeks after POST (WAPOST) application. However, PRE-applied Zidua alone or with Engenia, Engenia alone, Spartan + Zidua, and Spartan + Sencor followed by a sequential POST application of a tank-mixture containing Engenia and Roundup PowerMax provided ≥ 95% kochia control at 6 WAPOST. Kochia biomass reduc­tion was > 92% with a majority of the treatments; exceptions were Zidua PRE alone (59% reduction), Engenia alone (76% reduction), and Zidua + Engenia (88% reduc­tion) treatments. Soybean grain yield for a majority of the tested treatments did not differ, and ranged from 23 to 25 bu/a. These results suggest that effective PRE herbi­cide options are available for managing glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybean.

Recommended Citation

Kumar, V.; Liu, R.; Lambert, T.; and Stahlman, P. W. (2019) "Herbicide Strategies for Managing Glyphosate- and Dicamba-Resistant Kochia in Roundup Ready 2 Xtend Soybean," Kansas Agricultural Experiment Station Research Reports: Vol. 5: Iss. 6. https://doi.org/10.4148/2378-5977.7791