Individual and combined effects of herbicide tribenuron-methyl and fungicide tebuconazole on soil earthworm Eisenia fetida

Jiqiang Chen,Caixia Wang,Qingming Zhang,Wenxing Liang,Muhammad Saleem

doi:10.1038/s41598-018-21288-y

Jiqiang Chen, Caixia Wang + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-21288-y

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Abstract

Earthworms are soil engineers that alter the soil bio-physical properties to favor plant growth whereas pesticides represent a significant threat to their abundance and soil health. Thus, we investigated the toxic effects of tribenuron-methyl (TBM) and tebuconazole (TEB) on the soil earthworm, Eisenia fetida. The TBM demonstrated low toxicity to E. fetida in the contact filter paper and artificial soil tests, with median lethal concentrations (LC50) of 135.6 μg cm−2 at 48 h and 511 mg kg−1 on day 14, respectively. Similarly, TEB also showed low toxicity to E. fetida in the artificial soil test with LC50 of 287 mg kg−1 on day 14. However, TEB was highly toxic to earthworm in the contact filter paper test with LC50 of 5.7 μg cm−2 at 48 h. The mixture of two pesticides had an antagonistic effect on the earthworm. Under 0.1 LC50 of TBM and TEB, either single or combined application of pesticides induced oxidative stress and inhibited cellulase activity in early days of the earthworm exposure. However, both pesticides did not damage the earthworm DNA. Our results suggest that pesticides can negatively affect soil earthworms and provide valuable information regarding the responses of soil biological engineers to the lethal agrochemicals.

Highlights

The tribenuron methyl (TBM) demonstrated low toxicity to E. fetida in the contact filter paper and artificial soil tests, with median lethal concentrations (LC50) of 135.6 μg cm−2 at 48 h and 511 mg kg−1 on day 14, respectively
Pesticides used, alone or as mixture, did not cause significant damage to the earthworm DNA than that of control. Both acute and chronic toxicity tests play an important role in the risk evaluation of pesticides to earthworms and are considered valuable for predicting the responses of soil organisms to pesticides[5,28,29]
Artificial soil test represents to some extent the natural conditions, and it is recommended as a standard method by researchers and several research organizatios[29,31,32,33]

Summary

Introduction

The TBM demonstrated low toxicity to E. fetida in the contact filter paper and artificial soil tests, with median lethal concentrations (LC50) of 135.6 μg cm−2 at 48 h and 511 mg kg−1 on day 14, respectively. Under 0.1 LC50 of TBM and TEB, either single or combined application of pesticides induced oxidative stress and inhibited cellulase activity in early days of the earthworm exposure. The use of pesticides in agriculture is a common practice to protect crops all over the world Despite their impacts on target species, pesticides potentially affect soil macro- and microorganisms[1,2]. Pesticides in the agricultural soils rarely occur as single individual compounds, but rather, exist as mixtures with other chemicals including pesticides[9,10] Their occurrence with the other pesticides in soil may change and/or amplify their toxicity[4], the results from single pesticide exposures studies may not reflect real toxicological responses of earthworms when exposed to multiple pesticides in the field. Despite the individual effects of TBM and TEB on soil health indicators are studied, their combined effects on soil earthworms remain unknown

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