Comparative Analyses of Glyphosate Alternative Weed Management Strategies on Plant Coverage, Soil and Soil Biota

Lee Hudek,Lambert Bräu,Aydin Enez

doi:10.3390/su132011454

Abstract

Glyphosate-based foliar spray herbicides are the most common method for urban weed control due to their broad-spectrum and efficacy for burndown applications. As interest in glyphosate alternatives has increased in recent years, this project assessed the efficacy of the following non-glyphosate-based alternative weed management strategies: glufosinate, imazapyr, MCPA + dicamba, prodiamine, pine oil, clove oil, nonanoic acid, acetic acid + hydrochloric acid and steam against untreated (negative) controls and glyphosate-treated sites. Across all four seasonal treatments (winter, spring, summer and autumn), glyphosate and glufosinate reduced weed coverage (>65% after 4 and 12 weeks); imazapyr reduced weed coverage by >80% after 12 weeks; and steam reduced weed coverage by >80% after 4 weeks, and after 12 weeks showed to reduce weed coverage by >20% after the second application. The MCPA + dicamba, prodiamine, pine oil, clove oil, nonanoic acid and acetic acid + hydrochloric acid treatments had mixed impacts on weed coverage. Minimal alterations to soil physicochemical properties were observed across the two sites for all treatments. Assessment of impacts the different weed management strategies had on arthropod and microbial relative abundance showed minimal alterations; with only steam observed to reduce relative microbial abundance. Glufosinate, imazapyr and steam may be considered alternatives to glyphosate for reducing weed coverage but may not be as effective or have undesirable off-target effects. Overall, glyphosate provided the most consistent weed reduction at both sites over 12 weeks, without any recorded negative off-target or soil biota impacts.

Highlights

Introduced invasive plant species are controlled to maintain and preserve native flora and fauna in urbanised areas and revegetated habitat zones, prevent damage to infrastructure and to maintain aesthetically pleasing streetscapes and parklands [1]
Stock forms of glyphosate, pine oil, glufosinate, methyl-4-chlorophenoxyacetic acid (MCPA) + dicamba, acetic acid + hydrochloric acid, prodiamine and imazapyr were diluted in water to recommended working concentrations (Table 1) as specified by manufacturers
Site 1 has a heavy clay soil type

Summary

Introduction

Introduced invasive plant species (weeds) are controlled to maintain and preserve native flora and fauna in urbanised areas and revegetated habitat zones, prevent damage to infrastructure and to maintain aesthetically pleasing streetscapes and parklands [1]. There are many forms of weed control and, globally, the use of glyphosate-based herbicides is one of the most common approaches [8]. Glyphosate is a broad-spectrum and non-selective herbicide that was initially developed as an alternative to other herbicides that would cause uncontrollable crop damage, had lower efficacy, were subject to the development of resistance, or posed health risks to humans [9]. Glyphosate-based herbicides are the most popular choice for weed control based on their low cost, ease of application, target specificity and high efficacy for killing a broad range of weeds. Glyphosate was originally perceived as having low toxicity towards animals, recently, it has been suggested that glyphosate may lead to carcinogenesis in humans [10]. In 2017, the International Agency for Sustainability 2021, 13, 11454.

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