Using earthworm avoidance behaviour to assess the toxicity of formulated herbicides and their active ingredients on natural soils

Abstract

Background, aim, and scope Soil quality has been threatened by intensive agricultural practises, namely those relying on the application of pesticides, such as herbicides. Among the non-target terrestrial organisms exposed to such scenarios, earthworms are key ecological receptors widely used in ecotoxicological studies. As such, this work aims to assess the effects of two herbicide active ingredients (a.i.)-sulcotrione and penoxsulam-and their respective commercial formulations-MIKADO® and VIPER® (referred as Mikado and Viper)-on the avoidance behaviour of Eisenia andrei. In an attempt to enhance the ecological relevance of the generated toxicity data, the avoidance tests were run with standard (LUFA 2.2; L) and natural soils (from corn and rice fields), as long as their habitat function did not constrain the earthworm behaviour. Methodology Earthworms were bred in the lab before test conductance. The natural soils used as substrates were collected before the cropping season on corn (C) and rice (R) fields, which are integrated in a wide area exploited for agriculture. Their physico-chemical characterization evolved the determination of pH (H 2 O, KCl), conductivity, organic matter (OM) and clay/silt contents, and water-holding capacity (WHC). The avoidance tests intended to ascertain (1) the random distribution of earthworms in the natural soils C and R (dual-control tests), (2) the habitat function of natural soils against each other and against L soil, (3) the effect of active ingredients and formulated herbicides on E.andrei behaviour. Avoidance tests with the a.i.s were only performed in L soil. Data evaluation followed ISO (2005) guidelines.Results C and R soils presented higher OM (5.1% and 4.5%, respectively) and clay/silt (53.3 and 43.1, respectively) contents and WHC (107.2 and 109.9%, respectively) than L soil (4.1, 21.4 and 48.0%, correspondingly). Earthworms distributed randomly in dual-control tests, but preferred R soil significantly, relative to L or C soils. The LOEC and EC 50 values calculated for sulcotrione (>1,000.0 and 1,263.3 mg a.i. kg -1 , respectively) and Mikado (1,012.8 and 1,301.3 mg a.i. kg -1 , respectively) were much higher than those calculated for penoxsulam (100 and 80.6 mg a.i. kg -1 , respectively) or Viper (52.7 and 51.5 mg a.i. kg -1 , respectively), when L soil was used as substrate. Moreover, the habitat function of L soil contaminated with the formulated herbicide Viper was more constrained relative to that of the a.i. penoxsulam. Viper induced higher % avoidance on E. andrei exposed to the contaminated L soil compared to that under the R soil. Discussion The response of earthworms to R (attraction) and C (avoidance) soils could be related, not only to the quantity of OM content, but also to the quality of organic and inorganic fractions of soil, beyond other intrinsic properties of soils. Both Mikado and sulcotrione impacted the behaviour of E. andrei only slightly. This endpoint was more affected under penoxsulam or Viper exposures on L soil, being the latterformulated...

Effect of Triazophos and Pendimethalin on Avoidance Behavior of Eisenia fetida in Natural Soil of Kota (Rajasthan)

“…Li et al (2015) reported that at concentration of 0.1 mg/kg of Enrofloxacin, E. fetida showed attraction behavior. Marques et al (2009) found that E. Andrei showed attraction behavior at concentration of 31.7 mg/kg of formulated herbicide Mikado (a.i. is sulcotrione).…”

Integrated ecological risk assessment of pesticides in tropical ecosystems: A case study with carbofuran in Brazil

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Ecotoxicological effects of rice field waters on selected planktonic species: comparison between conventional and organic farming

“…The presence of toxic adjuvants in commercial pesticide formulations may also increase toxicity. Marques et al (2009) found that the behaviour of the earthworm Esenia andrei was affected under VIPER Ò exposures in soils, the formulated product being even more repulsive for E. andrei than the active ingredients benzofenap and clomazone. In our study, predicted TU, conductivity and suspended solids were at the upper tolerance range of the studied species (Barata et al 2006(Barata et al , 2009 and other unmeasured pesticides could also be present (Kuster et al 2008).…”