Efeitos do uso de triciclazol, propiconazol e tebuconazol em diferentes doses sobre o residual de fungicidas e a qualidade industrial do arroz irrigado

Abstract

Tricyclazole, tebuconazole and propiconazole are systemic fungicides, with a broad spectrum of action, and used to control diseases in rice. Depending on the management used in the application, the residues can persist until the moment of the harvest, resulting in the occurrence of residues above the tolerated limits. Regarding the quality of grains, studies are necessary to evaluate the effects of the application of fungicides in the field on the productivity and quality of freshly harvested and stored rice.In the present study, rice grains of the cultivar IRGA 424 RI were submitted to the application of tricyclazole, tebuconazole and propiconazole in phenological stages R2 and R4, with an interval of 14 days between applications. The recommended dose and twice the recommended dose for each active ingredient were tested. A control treatment without fungicide application was prepared. A randomized block design with three replications was used. In an investigation related to the conservation of grains according to the presence or not of residual fungicide, grains treated with the recommended dose for the three active ingredients and grains obtained from the treatment without application were dried up to 20% and 16% moisture and stored for up to 100 days at 32 °C. The analysis of liquid chromatography (LC) with mass spectrometry (MS) detection of residual fungicides in brown rice revealed no difference between the recommended dosage and twice the recommended dose for the active ingredients tricyclazole (0.01-0, 01 mg / kg) and tebuconazole (0.14-0.16 mg / kg). Propiconazole exhibited a higher residue level (0.20 mg / kg) with twice the recommended dose compared to that observed for grains treated with the recommended dose (0.11 mg / kg). Parboiled brown rice had 0.40 mg / kg of propiconazole and 0.21 mg / kg of tebuconazole. After polishing, the residue levels of these active ingredients were reduced to 0.18 mg / kg and 0.13 mg / kg, respectively. The grain yield of the plots treated with fungicides was higher than the control treatment, but no statistical difference was observed between the active ingredients. The weight of a thousand grains of fungicide-treated rice was greater than the control, mainly for treatments with propiconazole and tebuconazole. Head rice yield (67-68%) and rice whiteness (43.2-44.8 GBZ) were not impacted by the fungicide use, type of active ingredient or dosage. Further studies may consider other cultivars, field location, as well as a more adverse crop season for disease incidence than observed for this study. As for post-harvest conservation, grains that had propiconazole and tebuconazole residues had a lower incidence of Fusarium after a prolonged period of storage with higher grain moisture (20%). Tebuconazole also had an effect on Penicillium. In general, grains from application with propiconazole and tebuconazole showed less yellowing and maintained higher yield of whole grains after storage.