Measurement of reflectance has been shown an efficient, pratical and quick method to evaluate the efficiency of fungicides, in disease control. The objective of the work was to compare the use of reflectance measurement with visual disease assessment method to evaluate the efficiency of fungicides for the controlling Asian soybean rust relating the assessment data with yield. The assay was carried out in the Farm School of UEL, with the soybean cv. BRS 133, in randomized block design with seven fungicide treatments and control without fungicide, four replicates. Two sprayings were applied at the R2 (3% of severity) and R5.1, growth stages. Soybean rust severity was evaluated visually based on a rate scale and the percentage of solar radiation at 810 nm (R810), assessed with a multispecter radiometer. These data were use for stimating the area under of the disease progress curve (AACPD), and the area under of the curve of progress of the radiation (AACPR), respectively. The coefficient of determination (R2) for regression between variables AACPD x productivity was 0,79 between AACPR x productivity was 0,90 and AACPD x AACPR was 0,89. The data had demonstrated that the measurement of reflectance use (R810) allowed the separation of the fungicide treatments in three distinct groups, being epoxiconazol with lesser efficiency, metconazol, tebuconazol and piraclostrobina + epoxiconazol classified as intermediate and azoxistrobina + ciproconazol and picoxistrobina + ciproconazol as the most efficient treatments.
Phytopathometry; remote sensing; multispectral radiometer; Phakopsora pachyrhizi
