Thiamethoxan nanoformulations: studies of controlled released, soil leaching and determination of pesticide residue in orange leaves.

Abstract

Huanglongbing (HLB) is probably the most serious disease of citrus, nowadays. The severity of disease is mainly the rapid and efficient dissemination of the bacteria associated with HLB by psyllids Diaphorina citri (D. citri) and the absence of genetic resistance in citrus.Chemical control is the main way to control the psyllids, and there are different insecticides registered for this purpose. Thiamethoxam (neonicotinoid insecticide) is one of the active ingredients used in the control of HLB. This pesticide is highly water soluble, shows leaching potential, and it is rapidly degraded by photolysis. Due to the large losses that occur, whether due to application techniques used, environmental conditions, leaching and degradation by photolysis, concentrations below the effective concentration for disease control are observed, new applications are required. These repeated and indiscriminate applications result in use of the pesticide in amounts greater than those needed to control of the disease and results in several problems, such as increase of treatment costs, contamination of surface and underground water bodies, populations of D. Citri resistant to insecticide, and risks to human health, aquatic invertebrates and bees. Pesticide formulations nanocapsules allow a controlled release of active as well as protection against their premature degradation, allowing the use of conventional insecticide in a more sustainable way. Thus, studies of the effectiveness of encapsulated pesticide formulations are extremely important for enabling its use in agriculture. In this project, the insecticide thiamethoxam will be encapsulated in polymeric particles prepared from poly-µ-caprolactona (PCL) a biodegradable polymer by nanoprecipitation method. These particles will be characterized by size and morphology. The loading capacity of the nanoencapsulated insecticide and for the controlled release efficiency will be developed an analytical method for the quantification of thiamethoxam, by liquid chromatography-mass spectrometry (LC-MSMS). Methods for the quantification of thiamethoxam in orange leaves, as well as the identification of possible metabolites will be developed and also validated by LC-ESI -QToF / MSStudies related to toxicity of the nanoformulation will be held against Artemia salina microcrustacean. (AU)