How may Climate Change affect the activity of Glyphosate on Weeds? Some reflections

Khawar Jabran, Nimal Chandrasena, Taseer Ahmad and Ali Ijaz

Keywords:

Climate change, eCO2, global warming, weeds, crops, glyphosate, herbicidal activity

Abstract:

The evidence of changes in the global climate being felt by all of the bio-physical environments on the Earth is undisputed. Well-established literature, some of which is summarized herein, shows that the climate change effects will modify agro-ecosystems, including the multiple interactions between crops and weeds. From the perspective of weed management, there is compelling evidence that climate change effects will alter the growth of both C3 and C4 weeds and C3 and C4 crops in their interactions in cropping environments. Such responses will not just modify the outcomes of weed-crop competition, but also affect the efficacy of weed management methods, including the performance of herbicides. Glyphosate [N-(phospho-methyl) glycine] is unquestionably the world’s most used and successful herbicide. Published research, over at least three recent decades, indicates that glyphosate’s efficacy and activity on specific weeds may increase or decrease in the wake of elevated atmospheric carbon dioxide (eCO2) concentrations, global warming and associated climate change effects (such as increased or decreased rainfall and droughts). Changed glyphosate activity under climate change has been attributed to several factors. These include modified plant morphology and physiology (e.g., lower number of stomata, increased leaf thickness and modified cuticle permeability, etc.), which affects plant uptake and also changes in translocation of the herbicide to metabolically-active target sites. However, there is also evidence that, under some conditions, glyphosate activity on specific weedy taxa or groups of weeds may not be adversely affected by the dominant climate-modifying factors. In this article, we appraise some of the published evidence on glyphosate and reflect upon those factors and how the growth and vigour of weedy taxa might affect the efficacy of glyphosate, under eCO2 and a warmer global climate. In our view, aside from the broad generalizations, the effects of eCO2 and warming on glyphosate efficacy on major weeds cannot yet be discerned without more directed research.