2,4-D丁酯水剂防除水葫芦的效果及其在水中的残留动态

Control Effect of 2,4-D Butyl Ester on Water Hyacinth and Its Degradation Dynamics in Water

采用枯叶指数、枯柄指数、新根抑制、鲜重防效等指标,评价2,4-D丁酯对水葫芦的防除作用,并测定其在水中的残留动态。盆栽毒力测定结果表明,2,4-D丁酯对水葫芦根、叶柄、叶片毒力较强,LC50分别为20.45、573.8、781.82mg·L-1;而对鲜重的毒力较弱,LC50为2880.29mg·L-1。水域测定结果表明,1.80g·L-1剂量药后40d,对叶片的防除效果及新根抑制率均达100%,2.40g·L-12,4-D丁酯对各防治指标的防除效果均达100%。2,4-D丁酯控制叶片及新根的速效性较好,2.40g·L-1处理10d后对叶片、新根的控制效果分别达到83.76%、82.61%。采用气谱法测定水中水葫芦不同覆盖度和不同施用量条件下2,4-D丁酯的残留量,0h残留量为0.1193～0.4320mg·L-1,均超过0.07mg·L-1残留标准;24h残留量为0.0017～0.1766mg·L-1,除无水葫芦覆盖的水体施用量为3.60和2.40g·L-1的72%2,4-D丁酯残留量超过或略超标准外,其他处理均未超标准。48h残留量为0.0014～0.052153mg·L-1,均未超标准。

The control of Eichhornia crassipes Sloms by 2,4-D butyl ester were evaluated by withering leaf index, withering petiole index, the inhibition of new roots and fresh weight, and the dynamics of 2,4-D butyl ester residues in water was also analyzed. The 2,4-D butyl ester showed high toxicity to root, lamina and petiole of E. crassipes in the pot experiment, and the LC50 to root, lamina and leafstalk of E. crassipes reached 20.45, 573.8 and 781.82 mg·L^-1, respectively. Relative low toxicity of 2,4-D butyl ester to fresh weight and petiole length of E. crassipes were also found, with the LCs0 to fresh weight being 2 880.29 mg·L^-1. The control of E. crassipes with 2,4-D butyl ester was also conducted in the field. 1.80 g·L^-1 of 2,4-D butyl ester may get rid of all leaves and inhibit all new roots. 2.40 g·L^-1 of 2,4-D butyl ester showed 100% control efficiency to all tested tissues after 40 d treatments, and could quickly control the lamina and new roots with the control rates 83.76% and 82.61% after 10 d treatments, respectively. The residues of 2,4-D butyl ester in water covered with 0%, 60% and 90% density of E. crassipes were analyzed. The residues of 2,4-D butyl ester with immediate test after the use of 0.119 3～0.432 0 mg·L^-1 ranged from 0.119 3 to 0.432 0 mg·L^-1, which exceeded 0.07 mg·L^-1, the residue limits. After 24 h, the 2,4-D butyl ester residues in water without E. crassipes exceeded 0.07 mg·L^-1 under the treatments with 3.60 g·L^-1 and 2.40 g·L^-1 2,4-D butyl ester, but those under the other treatments were lower than the residue limits. After 48 h, the 2,4-D butyl ester residues were 0.001 4～0.052 153 mg·L^-1, not beyond the standard.