Ecotoxicidade do óleo essencial de canela e do inseticida imidacloprido: efeitos individuais e em mistura

Abstract

The increasing use of chemicals in agriculture, especially pesticides, has raised concerns about their environmental impacts, despite their productive benefits. Among these compounds, the insecticide imidacloprid (IMI) stands out, widely used to control sucking insects. In contrast, essential oils extracted from plants, such as cinnamon, have been investigated as potential natural alternatives to synthetic pesticides. However, the ecotoxicological effects of these natural compounds are still poorly understood, especially when used in mixtures with synthetic pesticides. Therefore, the present study aimed to evaluate the individual and combined ecotoxicological effects of cinnamon essential oil and imidacloprid on springtails of the species Folsomia candida, in tropical artificial soil (TAS). Chronic toxicity tests were performed based on ISO 11267, under a temperature regime of 20 ± 2 °C and a photoperiod of 12:12 h (light:dark). The tested concentrations were established based on the commercial doses (CD) for each substance. For IMI, the concentrations corresponding to 0.25CD; 0.50CD; 1CD; 2CD and 4DC were evaluated. In the case of cinnamon essential oil, the dose of 1 liter per hectare was adopted as a reference, testing concentrations equivalent to 1x; 2x; 4x; 8x; 16x; 32x and 64x this dose. To evaluate the mixtures, a factorial combination between two concentrations of cinnamon essential oil (1CD and 2CD) and the five concentrations of IMI was used. The results showed that imidacloprid was approximately 70 times more toxic than cinnamon essential oil when evaluated separately [EC₅₀ of 1.69 (87.17 - 149.61) μL kg-1 and 118.39 (1.25 - 2.14) μL kg-1 respectively]. Furthermore, when the pesticide was tested in mixture with cinnamon oil, the tested mixtures showed greater toxicity than the isolated insecticide, with EC₅₀ of 1.43 (1.18 - 1.68) μL kg-1 and 1.09 (0.92 - 1.25) μL kg-1 (mixture with 1CD and 2CD of the oil). Although the isolated essential oil is less toxic, its combination with imidacloprid intensified the adverse effects.