Resumo

KULCZYCKI, C et al. Cinética de degradación y persistencia de clorpirifós en mandarinas y naranjas del Noreste argentino (NEA). RIA. Rev. investig. agropecu. [online]. 2012, vol.38, n.3, pp.282-288. ISSN 1669-2314.

Legal normatives for pesticides residues are becoming more restrictive. Frequently, significant reductions are applied to the Maximum Residue Levels (MRL), including in some cases, prohibition of their use. Modern phytosanitary strategies must consider insecticide residue levels as well as dissipation rates in fruits in order to overcome increasing pesticide restrictions and reducing both toxicological and commercial risks. Argentine legislation for chlorpyrifos, a widely used insecticide for controlling different citrus pests, establishes MRL of 0.3 mg/kg for whole fruits including a Pre-Harvest Interval (PHI) of 21 days. These values coincide with those established by the European Union (EU), except for mandarins, and also with those of the Russian Federation. In this paper, degradation rates and persistence of chlorpyrifos were studied on two orange and three mandarin varieties. Assays were performed using chlorpyrifos 48 (emulsifiable concentrate), suspending 120 cm³ in 100 L of water using an air blast sprayer and volumes of 2000 to 2500 l/ha. Pesticide degradation in fruit was studied for a 120-day period since insecticide application and fruit samples were taken a different time intervals. Experimental data were used to perform a mathematical model where degradation was considered as a function of time. In all cases, initial residue levels were found above MRL established for the national legislation, while dissipation followed a logarithmic model. Dissipation of chlorpyrifos followed a fast rate till PHI was reached, with 69 to 82% of insecticide residues being eliminated. Since then, dissipation rates were slower than initially, reaching at the end of the experiment levels of 0.03-0.01 mg/kg. Residue levels of chlorpyrifos were below the MRL of Argentina´s and export countries legislation at the moment PHI was reached. However, presence of residues at the end of the assay showed great persistence of chlorpyrifos in citrus fruit.

Palavras-chave : Pesticide residues; Dissipation curve; Legislation.

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