Climate Change Influence on Herbicide Efficacy and Weed Management

Climate change refers to a change in the climate system that persists for long periods of time, irrespective of the cause. Since the industrial revolution, climate change has been more often associated with a rise in the concentration of greenhouse gases such as carbon dioxide (CO2), methane, nitrous oxide, and halocarbons. The concentration of atmospheric CO2 is steadily rising and is expected to reach ∼1000 μmolmol−1 by the year 2100 with a simultaneous increase of 2–4∘C in the earth’s annual surface temperature (IPCC, 2013). Human activities such as the burning of fossil fuels and deforestation have contributed to a large extent to the emission of greenhouse gases (IPCC 2013, MacCracken et al., 1990). Continued emission of these gases may lead to unprecedented climate changes involving high global temperatures, erratic precipitation and wind patterns, and weather extremities such as droughts, floods, and severe storms (Tubiello et al., 2007; Robinson and Gross, 2010; Gillett et al., 2011; Coumou and Rahmstorf, 2012). Such extreme weather events and rapid climatic changes will have major impacts on the stability of ecosystems; consequently influencing plant life and agriculture (Dukes and Mooney, 1999). Crop production and agronomic practices involving weed management and pest control may be severely affected by these altered abiotic conditions primarily caused by changes in climate and climate variability (Dukes et al., 2009, Singer et al., 2013). Warmer and wetter climates not only affect weed growth but also change chemical properties of certain herbicides; thereby altering their performance on weeds and their control (Poorter and Navas, 2003; Dukes et al., 2009). Determining the response of weeds and herbicides to increased CO2 levels and associated changes in other climate variables is critical to optimize weed management strategies in the context of climate change. This chapter provides an overview of the impacts of climate change factors on weed growth and herbicide efficacy, particularly focusing on the impacts of climate factors on the underlying physiological mechanisms that determine herbicide performance.