Control of invasive plants at high latitudes with persistent herbicides: understanding persistence, to manage pesticide residues and achieve effective control

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Author
Graziano, Gino
Chair
Zhang, Mingchu
Committee
Mulder, Christa P. H.
Seefeldt, Steven
Tomco, Patrick
Keyword
Soils
Herbicides
Invasive plants
Aminopyralid
Clopyralid
Prunus padus
Metadata
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URI
http://hdl.handle.net/11122/15968
Abstract
Invasive plants are considered a problem in management of natural resources and maintenance of ecosystem services in Alaska. Persistent herbicides are often used to control invasive plants because of increased duration and efficacy of control; however, applicators must understand that persistence impacts rotations to sensitive crops or restoration to sensitive desirable species. The purpose of this study was to define and document the impacts of aminopyralid and clopyralid degradation and movement in boreal ecosystems when used in agricultural settings or applied to Prunus padus, a problematic invasive tree in the boreal ecosystem. In laboratory microcosms clopyralid did not adsorb to soil particles under any conditions. Aminopyralid adsorbed to soil particles with increased adsorption at lower pH due to protonation of the amine group. Amnopyralid and clopyralid were compared in agricultural field treatments of fallow ground, followed by two years of small grain production before rotation to field peas, a sensitive species in the third year. Herbicide was detected one year after treatment with both herbicides, but by two years after treatment only aminopyralid was detectable in soil. Bioassays performed with these same soils had a similar pattern with smaller plants 1 and 2 years after treatment, but no indication of herbicide 3 years after treatment. Despite the lack of detection in soils, herbicide sensitive field peas were unable to grow in aminopyralid treated plots 3 years after treatment, indicating the presence of biologically significant concentrations of herbicide. Aminopyralid applied to stems of invasive Prunus padus saplings was exuded from the roots of treated trees, with herbicide detected in soils and resulting in damage to some susceptible species. Applications of triclopyr resulted in the detections of herbicide and observations of non-target damage without significant change in defoliation of the target trees. Reduced rates were equally effective for aminopyralid.
Description
Dissertation (Ph.D.) University of Alaska Fairbanks, 2025
Table of Contents
Chapter 1: Introduction - non-native plant invasion in Alaska and their control with herbicides -- 1.1 Non-native plant invasions in Alaska -- 1.2 Need for control of invasive plants and cost and benefit of herbicides -- 1.3 Persistent herbicides used to control invasive plants in Alaska -- 1.4 Fate of pesticide residues in subarctic Alaska and impact to non-target vegetation -- 1.5 Isotherms of soil contaminant attenuation help understand persistence -- 1.6 Literature cited. Chapter 2: Persistence of aminopyralid and clopyralid in Alaska soils, and the role of pH on sorption and desorption in liboratory microcosms -- 2.1 Abstract -- 2.2 Introduction -- 2.3 Materials and methods -- 2.3.1 Soils and research sites -- 2.3.2 Field treatments -- 2.3.3 Crepis tectorum bioassays for herbicide detection -- 2.3.4 1H/31P NMR titrations for the determination of pKa -- 2.3.5 Computational determination of pKa -- 2.3.6 Soil-water partitioning of herbicide -- 2.3.7 Soil-water partitioning coefficients and freundlich isotherms -- 2.3.8 Herbicide extraction from aqueous phase of soil: water isotherms and field treated soils -- 2.3.9 HPLC-QQQ analysis -- 2.3.10 Statistics -- 2.4 Results and discussion -- 2.4.1 Field soil herbicide concentration, peas yield, and bioassays -- 2.4.2 Zwitterionic character of picolinic acid herbicide derivatives -- 2.4.3 soil sorption and desorption -- 2.5 Literature cited. Chapter 3: Herbicides in unexpected places: non-target impacts from tree root exudation of aminopyralid and triclopyr following basal bark treatments of invasive chokecherry (Prunus padus) in Alaska -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Materials and methods -- 3.3.1 Study sites -- 3.3.2 Efficacy of control and non-target impacts -- 3.3.3 Soil sampling -- 3.3.4 Aminopyralid root exudation isolation of drip-off effect -- 3.3.5 Bioassays -- 3.3.6 Herbicide soil quantification -- 3.3.7 statistical analysis -- 3.4 Results and discussion -- 3.4.1 Field experiments -- 3.4.2 Basal bark treatments -- 3.4.3 Non-target impacts to vegetation -- 3.4.4 Aminopyralid root exudation isolation of drip-off effect -- 3.5 Literature cited. Chapter 4: Reduced rates of aminopyralid for basal bark treatments of Prunus padus in Alaska decrease non-target impacts without changing efficacy of control or recovery of desirable vegetation -- 4.1 Abstract -- 4.2 Introduction -- 4.3 Materials and methods -- 4.3.1 Study sites -- 4.3.2 Study design and plot set up -- 4.3.3 Soil sampling -- 4.3.4 Control and non-target impact evaluation -- 4.3.5 Analytical herbicide detection -- 4.3.6 Statistics -- 4.4 Results and discussion -- 4.4.1 Herbicide treatment and impact to target species -- 4.4.2 Rates and herbicide detection -- 4.4.3 Rates impact to frequency of non-target impact -- 4.5 Literature cited. Chapter 5: Conclusion - understanding herbicide residues impact to beneficial vegetation after invasive Prunus padus control in forests and weed control in grain production -- 5.1 Synthesis of research -- 5.2 Further directions -- 5.3 Literature cited.
Date
2025-05
Type
Dissertation
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