Antagonistic Effect On The Lethality of Earthworm (Eisenia Fetida L.) Being Exposed To Binary Mixtures of Herbicides

Abstract Frequent use of herbicides might impose a risk for non-target species. The objective was to test the combined toxic effect of binary herbicide mixtures: metribuzin:halosulfuron and metribuzin:flumioxazin on non-target earthworms in two test systems, a filter paper, and a soil toxicity test system. The joint action experiments were independently run twice to substantiate the findings. The most potent individual herbicide was metribuzin with a 50% lethal concentration (LC50) of 17.17 µg ai. cm− 2 at 48 h in filter paper test. The toxicity of the individual herbicides on filter paper test was ranked as metribuzin > halosulfuron > flumioxazin. In a soil test, metribuzin and halosulfuron had high toxicity with the LC50 8.48 and 10.08 mg ai. kg− 1 on day 14. Thus, the individual herbicide ranking did not change between the filter paper and artificial soil tests. The herbicides' mixed effect showed in both test systems consistent antagonistic effect relative to a Concentration Addition reference model. It means that the mixtures retracted the herbicides' action in the earthworms.