Steddom K, Bredehoeft M W, Khan M, Rush C M
Texas Agricultural Experiment Station, Amarillo, TX 79106.
Southern Minnesota Beet Sugar Cooperative, Renville, MN 56284.
Plant Dis. 2005 Feb;89(2):153-158. doi: 10.1094/PD-89-0153.
Visual assessments of disease severity are currently the industry standard for quantification of the necrosis caused by Cercospora beticola on sugar beet (Beta vulgaris) leaves. We compared the precision, reproducibility, and sensitivity of a multispectral radiometer to visual disease assessments. Individual wavebands from the radiometer, as well as vegetative indices calculated from the individual wavebands, were compared with visual disease estimates from two raters at each of two research sites. Visual assessments and radiometric measurements were partially repeated immediately after the first assessment at each site. Precision, as measured by reduced coefficients of variation, was improved for all vegetative indices and individual waveband radiometric measures compared with visual assessments. Visual assessments, near-infrared singlewaveband reflectance values, and four of the six vegetative indices had high treatment F values, suggesting greater sensitivity at discriminating disease severity levels. Reproducibility, as measured by a test-retest method, was high for visual assessments, single-waveband reflectance at 810 nm, and several of the vegetative indices. The use of radiometric methods has the potential to increase the precision of assessments of Cercospora leaf spot foliar symptoms of sugar beet while eliminating potential bias. We recommend this method be used in conjunction with visual disease assessments to improve precision of assessments and guard against potential bias in evaluations.
目前，对甜菜（Beta vulgaris）叶片上由甜菜尾孢菌引起的坏死进行量化的行业标准是疾病严重程度的视觉评估。我们比较了多光谱辐射计与视觉疾病评估的精度、可重复性和灵敏度。将辐射计的各个波段以及根据各个波段计算的植被指数，与两个研究地点的两名评估人员的视觉疾病估计值进行了比较。在每个地点进行首次评估后，立即部分重复进行视觉评估和辐射测量。与视觉评估相比，所有植被指数和各个波段辐射测量的精度（以降低的变异系数衡量）都有所提高。视觉评估、近红外单波段反射率值以及六个植被指数中的四个具有较高的处理F值，表明在区分疾病严重程度水平方面具有更高的灵敏度。通过重测法测量的可重复性，对于视觉评估、810 nm处的单波段反射率以及几个植被指数来说都很高。使用辐射测量方法有可能提高甜菜尾孢叶斑病叶部症状评估的精度，同时消除潜在偏差。我们建议将这种方法与视觉疾病评估结合使用，以提高评估精度并防范评估中的潜在偏差。
