Soil Toxicity Assessment of Fungicide Containing Thiram 80% WP Using Eisenia fetida and Allium cepa as Indicator Species

Abstract

Abstract Agrochemicals are used extensively in fields to kill pests and weeds which can exert toxic effects on other non-target species including Earthworms and Common Onion. This research was conducted to evaluate toxic effects of a commercial fungicide containing Thiram 80% WP (Wetting Powder) which is dimethyldithiocarbamate on Eisenia fetida (Earthworms) and Allium cepa (Common Onion). Earthworms are better indicators of the health of soil because 60% − 80% of soil biomass represents Earthworms. Allium cepa is considered as an efficient bio-indicator in toxicity testing, because of the rapid root growth rate and cost effectiveness. Acute toxicity of fungicide Thiram 80% WP was evaluated. Eisenia fetida was exposed to five different concentration solutions directly (6 mg/L, 8 mg/L, 10mg/L, 12mg/L, and 14 mg/L) for 48 hours, and in artificial soil (45, 90, 135, 180 and 225 mg/kg) for 14 days and as a control distilled water was used. After the exposure to Thiram 80%, WP mortality of Eisenia fetida increased along the concentration gradient. Overall results indicate LC50 value of 12.636 mg/L and 140.138 mg/kg respectively in solution and artificial soil. In both solution and artificial soil exposure, abnormal behaviour like high movement rates could be observed. Acute toxicity was evaluated to Allium cepa, by 72 h experiment of root growth with a range of fungicide concentrations (40 mg/L, 80 mg/L, 120 mg/L, 160 mg/L, and 200 mg/L) and as control tap water was used. Overall results indicate EC50 value of 22.548 mg/L. According to overall data, tested fungicide Thiram 80% WP can be toxic to non-target organisms when exposed in concentrations below LC50 and EC50 but further chronic and genotoxic evaluations must be conducted.