Assessment of the toxicity of a 2,4-D herbicide to the earthworm Eudrilus eugeniae Kinberg, 1867 (Oligochaeta, Eudrilidae)

2,4-D is commonly used in the world to control undesirable plant species in monocotyledonous fields. The massive use of this herbicide requires knowledge of its ecotoxicological spectrum for better regulation of its use. This study aimed to characterize acute toxicity and to determine the long-term effects of a 2,4-D herbicide on Eudrilus eugeniae. The tests were carried out in Azaguié (Côte d’Ivoire), on natural soil enriched with rabbit droppings. The lethal concentration (LC50) was 175.6±12.3 mg/kg. The exposure of earthworms to 20 mg/l of 2,4-D (9.2 mg/kg) reduced significantly cocoon production, hatching rate and juvenile’s number per cocoon. With regard to these results, we concluded that 2,4-D based herbicides are potential threat to earthworms because CL 50 was largely below concentrations of 1920 mg/l and 2880 mg/l of 2,4-D recommended by the manufacturer.

Keywords: 2,4-D, Eudrilus eugeniae, formulation, acute toxicity, long-term effect.