Laboratory tests were conducted to compare the effects of various concentrations of glyphosate and 2,4-D on earthworms (Eisenia foetida) cultured in Argissol during 56 days of incubation. The effects on earthworm growth, survival, and reproduction rates were verified for different exposure times. Earthworms kept in glyphosate-treated soil were classified as alive in all evaluations, but showed gradual and significant reduction in mean weight (50%) at all test concentrations. For 2,4-D, 100% mortality was observed in soil treated with 500 and 1,000 mg/kg. At 14 days, 30%-40% mortality levels were observed in all other concentrations. No cocoons or juveniles were found in soil treated with either herbicide. Glyphosate and 2,4-D demonstrated severe effects on the development and reproduction of Eisenia foetida in laboratory tests in the range of test concentrations.
Pesticides’ sublethal effects are not regularly taken into account when assessing agrochemical’s toxicity. With the objective of detecting chronic, sublethal effects of the widely used herbicide glyphosate, an experiment was performed using the earthworm Eisenia fetida as model organism. Earthworm adults were randomly assigned to three glyphosate treatments: control (no glyphosate), regular dose for perennial weeds, and double dose. Six E. fetida individuals were placed in each pot. Two random pots were taken weekly from each treatment and the number of adults, individual weight, number of cocoons, and presence and number of young earthworms were recorded. A matrix analysis was performed with the data. The matrix population model built showed that while the control population had a positive growth rate, both glyphosate treatments showed negative growth rates. The results suggest that under these sublethal effects, non-target populations are at risk of local extinction, underscoring the importance of this type of studies in agrochemical environmental risk assessment.
Non-target organisms can be at risk of local extinction due to agrochemicals chronic sublethal effects, which are not consistently taken into account in toxicity and risk assessment studies.
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