Growth of weeds and their chemical control under climate change conditions

Climate change has a great influence on weed growth and susceptibility of weeds to her­bicides. This study determined the effect of six herbicides on three weed species under different CO2 concentrations and temperature levels. The weeds in the study were: (i) wild oat (Avena fatua), (ii) lambsquarter (Chenopodium album), and (iii) wild mustard (Sinapis arvensis). The herbicides used in this study were: (i) 240 g ꞏ l–1 clodinafop-propargyl, (ii) 3% mesosulfuron-methyl + 0.6% iodosulfuron-methyl sodium + 9% mefenpyr-diethyl, (iii) 40 g ꞏ l–1 nicosulfuron, (iv) 480 g ꞏ l–1 glyphosate isopropylamine salt, (v) 75% tribenu­ron methyl and (vi) 3% mesosulfuron-methyl + 0.6% iodosulfuron-methyl sodium + 9% mefenpyr-diethyl + 300 g ꞏ l–1 bromoxynil + 300 g ꞏ l–1 MCPA. The study was carried out in a fully automated greenhouse which could be adjusted with desired CO2 concentra­tion and temperature. The weeds were exposed to three different temperatures (day/night 26/16 ± 1, 29/19 ± 1 and 32/22 ± 1°C) and CO2 (400 ± 50, 600 ± 50 and 800 ± 50 ppm) levels. A temperature of 26/16 ± 1°C plus a CO2 level of 400 ± 50 ppm was considered as the control. Results showed that 26/16°C × 800 ppm CO2 produced the highest plant length (65.05 cm), plant fresh weight (7.42 g) and plant dry weight (1.31 g) for A. fatua. Similarly, for S. arvensis, the same treatment showed the highest plant length (31.63 cm), plant fresh weight (23.99 g) and plant dry weight (1.82 g) while for C. album, different climatic condi­tions did not show a significant effect on the growth of this weed. The ED50 values of herbi­cides for controlling A. fatua, C. album and S. arvensis increased (112.8, 0.6 and 199.4) with an increase in temperature and CO2 levels, respectively. It is predicted that the control of some weeds will be difficult in the climate change that includes an increase in temperature and carbon dioxide in the future.