Climate Change’s Impacts on Weeds and Herbicide Efficacy: A Review

Abstract

Climate change is a natural and continuous process. But recent relatively rapid change in climate occurs due to anthropogenic activities which makes alarming attention because it contributes largely to global warming by affecting the greenhouse gases (GHGs) and aerosols. GHGs mainly CO 2 , methane, nitrous oxide CFC11, CFC12, HCFC22and HFC23 with different global warming potential accumulate in atmosphere and increase in concentration over time creating the so called "greenhouse effect". This effect can alters balance by transmitting incoming solar radiation but absorbing outgoing thermal radiation from surface. Atmospheric CO 2 rose from 280 to 387 μmolmol -1 from 1750 to 2007 and expected to reach 600 μmolmol -1 by 2050 and global earth surface temperature is likely to rise in a range of 1.1 to 6.4°C during the 21st century due to the rising CO 2 concentration. Weeds are complex in nature and have significant negative effect on agriculture. Chemical weed control becomes major choice/tool because of its economic, easy to use, greater efficacy, due to scarcity of labour and time saving. Climate component viz., light, CO 2 , temperature, precipitation, humidity, wind, environmental stress etc. affect crop-weed competition and efficacy of applied herbicides. Light stimulates weed seed development and leaf shape. Light is the source of energy for photosynthesis and the rate of photosynthesis determines the rate of phloem translocation of assimilates and subsequent phloem translocation will increase the movement of foliar-applied systemic herbicides. Most crops are C 3 and most weeds are C 4 , and hence weed competition will consequently decrease as CO 2 increases, should not be viewed as universal axiom as there are four major C 4 crops of economic importance (corn, pearlmillet, sorghum, and sugarcane), and their many important C 3 weeds. Increasing CO 2 concentration increases the starch concentration in tissue and reduces the protein content leads to less demand of amino acids synthesis which alters the efficacy of ALS inhibitors herbicides. High temperature shortens the growth phases, stimulate stomata conductance and lowers the viscosity of cuticular lipids leads to increase permeability and diffusion of herbicides through the cuticle. Warmer temperature also reduce uptake of herbicides due to rapid drying of droplets. Increasing temperatures may mean an expansion of weeds into higher latitudes or higher altitudes.. Increased cuticle thickness and leaf pubescence in response to drought, will also reduce herbicide entry into leaves. At higher humidity leaf retention time of herbicides mainly hydrophilic increases. Blowing wind may cause spray drift or dry up the spray droplet. So there is need to pay special attention and to study the impact of climate factors on weed life, crop-weed competition and herbicide efficacy so that adaptation and mitigation strategies can be developed for changing climate. K e y w o r d sClimate changes, Natural process, Greenhouse effect, Environment.

Effect of Multifunctional Adjuvants on Physical and Chemical Features of Spray Liquid and Efficacy in Sugar Beet

“…The optimum temperature for herbicide action is between 10-20 and 25 • C, because under these conditions the physiological processes of both the crop and the weeds are at their optimum level [9]. The action of herbicides is favored not only by moderate temperature but also high humidity (at least 60-70%) [16], because of better wetting of plants [17], increased retention [18], and reduced evaporation of droplets [19]. The uptake and high efficacy of herbicides are more dependent on the humidity of the air after application than during.…”

“…The temperatures at REC Złotniki during herbicide application in each year of the study were favorable for herbicide activity, as the temperature did not fall below 15 • C during the treatments, with the exception of the second treatment in 2019-12.0 • C. It was also not higher than 20 • C, with an air humidity of 58%, but most often between 60 and 80%. However, assuming that favorable conditions for herbicide activity are temperatures between 10 and 20 • C [16] and air humidity over 60%, it can be assumed that thermal conditions were not the worst in this case either, as were the average daily air temperatures in the following several days after treatment.…”

Ten Ways That Weed Evolution Defies Human Management Efforts Amidst a Changing Climate

“…Drier conditions predicted under climate change, including more frequent droughts may decrease herbicide efficacy in at least two distinct ways: by reducing absorption of herbicides in weed roots or by reducing herbicide absorption in weed leaves that develop thicker cuticles to resist drought conditions [114][115][116]. Taken together, these lines of evidence collectively point to a serious loss in the expected effectiveness of herbicides, given future predicted climate regimes.…”

Sugarcane Production under Changing Climate: Effects of Environmental Vulnerabilities on Sugarcane Diseases, Insects and Weeds

“…Concentration of CO 2 has risen to 387 μmol mol −1 till 2007 and expected to reach 600 μmol mol −1 till 2050 [27]. Modern agriculture techniques is main driving force which contribute in 30% of greenhouse gas emissions [82]. Weeds have negative effects on agriculture and public health.…”