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Síntese, atratividade e eficácia de encapsulados sobre Atta sexdens (Hymenoptera: Formicidae)
(Universidade Federal de São Carlos, 2019-06-06) Gustani, Flávia Maria; Janegitz, Bruno Campos; https://lattes.cnpq.br/7746094938977989; Fujihara, Ricardo Toshio; https://lattes.cnpq.br/1863735094370774; https://lattes.cnpq.br/3515076570138144
Leaf-cutting ants (Hymenoptera, Formicidae, Attini) are defoliation pests of great agronomic importance The most effective control method is chemical, by using granulated baits containing sulfluramide as standard active ingredient. Therefore, the objective of this work was to develop an encapsulated based on chitosan and tapioca, compatible with the attractive ingredient (citrus pulp) and with the active ingredient (sulfluramide). For the synthesis of the encapsulates 30 mL of the chitosan solution, 6 mL of tapioca solution, 6 mL of acetone solution with sulfluramide and finally 3 g of citrus pulp were gradually added under constant stirring. The final solution was dripped in NaOH (1 mol) and after the precipitation process the encapsulates were subjected to Petri dish drying at 24°C for 2 days. In order to confirm the presence of sulfluramide in the encapsulated, Fourier Transform Infrared Spectrometer (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were performed. According to the characterizations made by FTIR, XRD and SEM, the presence of sulfluramide was confirmed in the synthesized encapsulated. To evaluate the attractiveness and the incorporation, the behavioral acts were observed regarding the foliar and encapsulated disks: to hold them on the fungus; lick its surface; puncture them into smaller fragments; pleating or gripping its edges; deposition of fecal fluid; incorporation in the fungus garden and deposition of hyphae on the newly incorporated fragments. There was rejection in the loading and the incorporation of encapsulated based on chitosan and tapioca in comparison to leaf discs. The most frequent behavioral acts in the processing of the encapsulated were: licking (21.53%), holding the encapsulated (21.41%) and loading the encapsulated (18.57%). The caste that most acted in the processing of encapsulated were the gardeners (50.59%). To evaluate the accumulated mortality of Atta sexdens workers were supply encapsulated without sulfluramide (ESA); encapsulated with 2% (m/v) sulfluramide (E2%); commercial bait Mirex™ (IGC). For that, evaluations were done at 1, 2, 3, 5, 7, 9, 11, 14, 17 and 21 days after treatment application, and the mortality was accounted per day. Mortality averages were corrected for the Abbott formula. The symptoms of intoxication corresponded to: t = tremors; l = slow movements; f = difficulty in moving legs; d = paralyzed front legs; p = paralyzed hind legs; i = all legs paralyzed, but antennas and gaster with normal movements; g = general paralysis. The non-parametric test Kruskal-Wallis was used for the analysis of the data at significance level (p<0.05), followed by test Student-Newman-Keuls. It was observed that in ESA the symptoms increased until the eleventh day, where the registered mortality rates were 64%. The E2% treatment presented symptoms from the first day and the 14th day all the workers were in dead. The treatment IGC, as in E2%, presented marked symptoms from the first day. On the ninth day of evaluation, it already had 100% of workers dead. Comparing the treatments between each other the mortality of E2% and IGC were significantly higher than in ESA. The encapsulated proved to have allowed the intoxication of workers causing mortality in the same proportion as the granulated baits.
Adsorção de tiametoxam em caldo de cana-de-açúcar (Saccharum spp) por carvão ativado nanomodificado e determinação por Cromatografia Líquida de Alta Eficiência (CLAE-DAD)
(Universidade Federal de São Carlos, 2019-06-06) Freitas, Driélle Aparecida de; Carrilho, Elma Neide Vasconcelos Martins; https://lattes.cnpq.br/5147872007117167; Nocelli, Roberta Cornélio Ferreira; https://lattes.cnpq.br/8934724759636382; https://lattes.cnpq.br/8723366953235952
The cultivation of sugarcane is one of the oldest in human civilization. In Brazil the species Saccharum officinarum is of greater importance for the sugar-alcohol sector due to its high levels of sucrose. Over time, several factors and conditions allowed Brazil to be one of the largest producers of this cultivar. However, in order to guarantee high productivity, high levels of pesticides are applied in this crop, among which the neonicotinoid and systemic insecticide thiamethoxam (TMX) stands out. Systemic insecticides applied in crops are of great concern due to the possibility of the consumption of their derivatives by humans and animals. Therefore, considering the sugarcane juice a food matrix and the risks that TMX residues can offer, the objective of this work was to develop and validate a chromatographic method for quantification of this pesticide, as well as to evaluate its removal from aqueous and sugarcane juice media by a magnetic activated charcoal nanocomposite (AC-NP). The synthesis of ACNP was performed by the coprecipitation method, and the composite was characterized by XDR, FTIR, and SEM. After TMX adsorption assays, the pesticide was quantified by High Performance Liquid Chromatography coupled with a diode array detector (HPLCDAD) at 254 nm. The chromatographic operating conditions were: mobile phase acetonitrile:water (30:70) at 1.0 mL min-1 flow rate; C18 column; sample injection volume 20 μL; and analysis time of 6 min. The main parameters of the validation presented satisfactory results, and the selectivity of the method for TMX was observed in both water and sugarcane media, with limits of detection and quantification of 0.057 and 0.17 mg L1, respectively, and 4.6 min retention time. The matrix effect was not observed and r2 ranged from 0.9958 to 0.9985. Recovery tests presented results between 91 and 103%, and the coefficient of variation range was 1.9 – 4.3%. The nanomodification process was satisfactory and the characterization of AC-NP allowed to observe the effective impregnation of the magnetite. The TMX adsorption kinetics in sugarcane juice by ACNP was a pseudo-second order type, with r2 of 0.9999, indicating a chemical adsorption process. The experimental sorption capacity (SC) for both TMX (standard) and TMX-FP (formulated product) were 13.3 and 65.7 mg g-1, respectively, and Freundlich and SIPS isothermal models best fit the TMX data (r2 = 0.9740 and 0.9716), while TMX-FP data were adjusted to Langmuir and SIPS (r2 0.9941 and 0.9943). Therefore, it was possible to conclude that the chromatographic method proposed for the quantification of TMX and TMX-FP in aqueous and sugarcane juice media was highly satisfactory, and validated for its main parameters. The efficiency of AC-NP in the sorption of this analyte was confirmed by the excellent values of SC and kinetics, indicating its favorable use in the removal of TMX from complex matrices.