Herbicidal control of deathcamas (Zigadenus paniculatus)

Authors: Stonecipher, Clinton - Clint; RANSOM, COREY - Utah State University; THACKER, ERIC - Utah State University; Welch, Kevin; Gardner, Dale; PALMER, MATT - Utah State University

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: 9/14/2020
Citation: Stonecipher, C.A., Ransom, C., Thacker, E., Welch, K.D., Gardner, D.R., Palmer, M. 2020. Herbicidal control of deathcamas (Zigadenus paniculatus). Weed Technology. 35(3):380-384. https://doi.org/10.1017/wet.2020.102 .
DOI: https://doi.org/10.1017/wet.2020.102

Interpretive Summary: Foothill death camas is a bulbous perennial native forb found throughout the western U.S. Death camas begins growth early in the spring, typically prior to other forages emerging. The lack of alternative forages at this time results in livestock consuming death camas and becoming poisoned. Research on herbicide control of death camas is limited to previous work from the 1950’s and 1960’s identifying 2,4-D as the only control agent. The objective of this study was to evaluate newer chemical control options for efficacy in controlling death camas and to determine if herbicide application alters the toxic alkaloid content of treated plants. Plots were established at two locations in Utah. Alkaloid concentrations did not change in herbicide treated death camas plants. The data from this study shows that 2,4-D, Crossbow®, and Plateau® are effective at controlling death camas on rangelands.

Technical Abstract: Foothill death camas is a bulbous perennial native forb found throughout the western U.S. Death camas begins growth early in the spring. The lack of alternative forages at this time can result in livestock becoming poisoned from the consumption of death camas. Research on herbicides for death camas control is limited to work from the 1950’s and 1960’s that identified 2,4-D as a control agent. The objective of this study was to evaluate alternative herbicide options for death camas control that include 2,4-D, 2,4-D + triclopyr, quinclorac, aminopyralid, imazapic, and chlorsulfuron. We also investigated the impact of plant growth stage on death camas control by making herbicide applications at two growth stages. One set of plots was treated with herbicides when death camas was in early vegetative and the second set treated at flowering. There is some evidence that stress might impact alkaloid content; therefore, we monitored alkaloid content of treated and non-treated death camas. Plots were established at Mt. Sterling, UT and Mt. Pleasant, UT. Death camas density was reduced in 2,4-D, 2,4-D + triclopyr, and imazapic treatments one- and two-years following herbicide application (P < 0.0001). Compared to the pre-treatment densities, death camas densities two years following herbicide application were reduced 96 ± 1.4%, 100 ± 0%, and 98 ± 0.9% for 2,4-D, 2,4-D + triclopyr, and imazapic at the Mt. Sterling site, respectively. At the Mt. Pleasant site, death camas density was reduced by 84 ± 2.8% with 2,4-D alone, while 2,4-D + triclopyr and imazapic provided similar density reductions as observed at the Mt. Sterling site. Steroidal alkaloid concentrations did not change in herbicide treated death camas plants at either stage of plant growth. These data indicate that 2,4-D, 2,4-D + triclopyr, and imazapic can effectively control death camas at both vegetative and flowering growth stages.