Impact of applying imazapyr on the control of Spartina alterniflora and its eco-environments in the Yellow River Delta, China

The invasion of Spartina alterniflora has threatened and damaged coastal wetlands in China, therefore, control and removal of this severe invasive plant are urgently needed. Green chemical control is an effective and low-cost method that can be used for large-scale removal of invasive specie. To study the control effect of imazapyr on S. alterniflora and evaluate its impact on other species and the wetland environment, a control experiment was set up in the Yellow River Delta Reserve in Shandong Province in May 2021. A total of 9 treatments were set up in the experiment: 25 % (W) imazapyr water (main agent), three treatments with dose gradients of 3.0, 6.0, and 9.0 L/acre, and the main agent at a dose of 6.0 L/acre with six treatments of AGE 809 (adjuvant A) and AGE 852 (adjuvant B) with dose gradients of 1.3, 2.6, and 5.2 L/acre, respectively. The results showed that after 60 days of application, the control efficiency of Spartina alterniflora was over 90 %, and the residual amount was small in the plots with the main agent additive < 6.0 L/acre. Among them, the residues on leaves were 0.499 ∼ 2.822 mg/kg, the residues in soil ranged from 0.0012 to 0.0714 mg/kg, and were from not detected in water to 8.8E-4 mg/kg. During the experiment, there were significant differences in soil physicochemical properties among different treatments, and imazapyr significantly affected on the availability of soil C, N, and P at the stage of large chemical residues (P < 0.05). In addition, imazapyr was not toxic to the benthic community and increased from 168.72/m³ to 633.75/m³ in 60 days after spraying. This study provides a theoretical basis, data support, and technical support for applying herbicides to control S. alterniflora in coastal wetlands of China.