Identifying alternative weed management strategies with regards to glyphosate usage

Currently, the most common method for weed control is to apply a glyphosate based-herbicide. Glyphosate has been the subject of much interest due to advances in understanding its off target toxicity, particularly, in humans where it potentially may lead to carcinogenesis. The manufacturer of the glyphosate-based herbicide “Round-up”, Bayer agreed to pay over US$ 10 billion to settle tens of thousands of claims surrounding deleterious health effects such as Non-Hodgkin’s lymphoma, due to repeated exposure and no adequate warning of potential effects from exposure included on the products safety label. Here a comprehensive desktop study was performed to identify all possible weed management alternatives that could replace glyphosate use in urban parklands. A short list of nine strategies was reached based on selection criteria of cost, availability, solubility, ease of use, any known off target toxic effects and known hazards for use, storage and the environment. The alternatives selected for testing against the control glyphosate were: glufosinate, imazapyr, nonanoic acid, acetic acid, clove oil, MCPA + dicamba, pine oil, steam and prodiamine. At two sites, one with a heavy clay profile and the other a sandy loam profile, the products were tested on ability to reduce plant coverage and effect on microbial abundance and diversity. At both sites steam showed to be a costly and time intensive, short-term chemical free option for reducing weeds, whereas, glufosinate was found to be as effective as glyphosate, and imazapyr even more effective than all other treatments – even after 16 weeks post application. Based on plate counts of bacteria grown from serially diluted soil samples, no treatments were found to significantly alter bacterial abundance or diversity in soil, however, more conclusive methods are being used to further assess this. Based on the evidence from the results here, glufosinate, imazapyr and steam offer feasible alternatives to glyphosate.