Refletância e avaliação visual como indicadores de severidade da ferrugem asiática, comparados à produtividade em soja

AUTOR(ES)

Alexandre José da Silva

DATA DE PUBLICAÇÃO

2009

RESUMO

The objectives of this study were to compare measurements of reflectance with methods of visual assessments in the patossistem Asian soybean rust aiming to quantify damage at different times and its correlation with yields and evaluate fungicides efficacy. The experiments were conducted in the Londrina, PR country, in the 2006/07 season. The test was repeated in two sowing dates in order to obtain variable intensity of the disease in different phenological stages of soybean. The experimental design was randomized blocks with 07 and 11 treatments and four repetitions, and each experimental plot was composed of five rows of six meters in length. To have gradient of disease, the treatments were applied in different seasons for applications of fungicide in the BRS 133. The severity of the disease was estimated at weekly intervals, beginning with appearance of first symptoms. The evaluations were made a reflectance radiometer with multiple-spectrum at eight a wavelength (460 to 810 nm). Visual assessments were performed weekly with the help of scale and diagrammatic scale. It was calculated the area under the disease progress (AUDPC) and the full measures of reflectance at 810 nm (AAR810). Measures of reflectance (R810) showed correlation with the yield (R2 = 76.7%) and defoliation (R2 = 90%). Compared to measures of visual assessment of Asian rust, the remote sensing method proved to be a quick, convenient and accurate, showing low levels of variation (CV = 4 and 5,2) while the traditional method of visual assessment showed higher values (CV = 17,59 and 23,1). The late sowing presented higher development of Asian soybean rust damage in Yield and higher (78.8%). Reflectances measure showed correlation with yield (89%) and provide better performance for damage assessment and fungicide test. Remote sensing showed potential for use in the quantification of damage caused by the Asian soybean rust.

ASSUNTO(S)

ferrugem asiática soja - doenças e pragas fungicidas - avaliação sensoriamento remoto phakopsora pachyrhizi soy-bean diseases and injuries fungicides evaluation remote sensing

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