Leandro Nascimento Marques

Equipamentos de pulverização aérea e taxas de aplicação de fungicida na cultura do arroz irrigado

O controle eficiente de doencas na cultura do arroz irrigado depende da selecao correta do equipamento, da taxa de aplicacao e da indicacao certa do produto quimico. O objetivo deste trabalho foi verificar a deposicao de gotas na cultura do arroz comparando-se bicos hidraulicos no sistema convencional, eletrostatico e atomizador rotativo de disco, em diferentes taxas de aplicacao por via aerea; para tanto, foram estudadas a densidade e a penetracao de gotas nos estratos medio e inferior, produtividade e rendimento de engenho do arroz. Os tratamentos avaliados foram: bico hidraulico 20 e 30 L ha-1, eletrostatico 5 e 10 L ha-1 e atomizador rotativo de disco 6, 10 e 15 L ha-1. Nao foram verificadas diferencas de produtividade e os equipamentos bico hidraulico 20 L ha-1 e atomizador rotativo de disco 15 L ha-1 proporcionaram maior rendimento de engenho. Maiores taxas de aplicacao usando-se bicos hidraulicos e atomizador rotativo proporcionaram maior penetracao e, consequentemente, tambem maior densidade de gotas nos dois estratos avaliados.

Elaboração e validação de escala diagramática para quantificação da mancha de isariopsis da videira

The lack of a standardized visual method may lead to inaccurate severity estimative and wrong conclusions. The objective of this research was to develop a diagrammatic scale to assess the severity of grape isariopsis leaf spot on grape, caused by Isariopsis clavispora. A diagrammatic scale with six levels of disease severity (1.60; 3.20; 6.60; 13.00; 24.10 e 40.24%) was developed and validated to assess grape isariopsis leaf spot. For validation, the severity of 30 leaves presenting different intensities of the disease was estimated by eight raters. Accuracy and precision were determined by linear regression and by the actual severity scale. This one provided good levels of accuracy and accuracy of visual estimation. The coefficient determination average was higher than 0.89, and absolute errors were lower than acceptable limits. The levels of accuracy, precision and reproducibility measurements of isariopsis leaf spot severity on grape significantly improved with the use of diagrammatic scale. The proposed diagrammatic scale proved to be adequate for severity assessments of grape isariopsis leaf spot.

Occurrence of mycotoxins in wheat grains exposed to fungicides on fusarium head blight control in southern Brazil

ABSTRACT Mycotoxins occurrence in wheat grains impose risks to human and animal health. The southern Brazil has favorable weather conditions for Fusarium graminearum infections and consequently for mycotoxins accumulation on grains. The goal of this study was to evaluate the behavior of new wheat commercial genotypes to Fusarium Head Blight (FHB), to control performance of new fungicide formulations and their relationship with mycotoxins concentration in grains. The manly mycotoxin occurrence on wheat grains in southern Brazil was deoxynivalenol (DON). Two cultivars showed high DON concentration above the tolerance limits (>3000 μg kg−1). Many other mycotoxins monitored presented concentrations below method detection limit. Satisfactory levels of fungicide effectiveness were achieved against F. graminearum. Some fungicides promoted a satisfactory decrease on DON accumulation in grains. The best results were obtained when prothioconazole was present. SDHI (Succinate dehydrogenase inhibitors) + QoI (Quinone outside inhibitors) fungicides showed benefic effects at FHB control at field, but it did not promote satisfactory reduction on DON contamination. Fungicides can be used satisfactory for FHB control and reduce DON contamination in grains in southern Brazil. The presence of prothioconazole should be recommended. Some genotypes showed high DON concentration and it was not directly related with FHB severity at field.

Tilletia barclayana: biologia e manejo em arroz irrigado

The rice kernel smut (Tilletia barclayana), which is considered as a secondary disease, lately has been growing in importance due to its high infestation levels and effects in seed yield. This disease is favored by elevated air temperatures and humidity; high nitrogen fertilizer rates a late sowing. In order to control it, the use or resistant varieties, appropriate sowing dates and balanced fertilization of the soil, are recommended practices.