CSIRO Land & Water, Clayton, Victoria, Australia.
CSIRO Health & Biosecurity, Dutton Park, Queensland, Australia.
Pest Manag Sci. 2018 Jan;74(1):246-255. doi: 10.1002/ps.4718. Epub 2017 Oct 24.
This study examines whether leaf spectra can be used to measure damage to cassava plants from whitefly (Bemisia tabaci), and the potential to translate measurements from leaf to landscape scale in eastern Africa. Symptoms of the cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) viruses, and sooty mould (SM) blackening of lower leaves from whiteflies feeding on the upper leaves, were measured at the leaf scale with a high-resolution spectroradiometer and a single photon avalanche diode (SPAD) meter, which retrieves relative chlorophyll concentration. Spectral measurements were compared to the five-level visual scores used to assess the severity of each of the three damaging agents in the field, and also to leaf chemistry data.
Leaves exhibiting severe CBSD and CMD were spectrally indistinguishable from leaves without any symptoms. Severe SM was spectrally distinctive but is likely to be difficult to map because of its occurrence in the lower crown. SPAD measurements were highly correlated with most foliar chemistry measurements and field scores of disease severity. Regression models between simulated Sentinel 2 bands, field scores and SPAD measurements were strongest using wavelengths with high importance weightings in random forest models.
SPAD measurements are highly correlated to many foliar chemistry parameters, and should be considered for use in mapping disease severity over larger areas. Remaining challenges for mapping relate to the subtle expression of symptoms, the spatial distribution of disease severity within fields, and the small size and complex structure of the cassava fields themselves. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
本研究旨在探讨叶光谱是否可用于测量白蝇（Bemisia tabaci）对木薯植株的损害，并探讨在东非将叶片测量值转化为景观尺度的可能性。采用高分辨率光谱辐射计和单光子雪崩二极管（SPAD）计（可获取相对叶绿素浓度）在叶片尺度上测量了木薯褐斑病（CBSD）和木薯花叶病（CMD）病毒的症状，以及白蝇在上部叶片取食导致下部叶片出现煤污病（SM）黑斑的情况。光谱测量结果与用于评估田间三种有害生物每一种严重程度的五级视觉评分进行了比较，同时也与叶片化学数据进行了比较。
严重感染 CBSD 和 CMD 的叶片与没有任何症状的叶片在光谱上无法区分。严重的 SM 在光谱上具有独特性，但由于其发生在下部树冠中，因此可能难以进行映射。SPAD 测量值与大多数叶片化学测量值和田间疾病严重程度的评分高度相关。模拟 Sentinel-2 波段、田间评分和 SPAD 测量值之间的回归模型在随机森林模型中使用具有高重要权重的波长时最强。
SPAD 测量值与许多叶片化学参数高度相关，应考虑用于更大面积的疾病严重程度映射。映射仍面临的挑战与症状的微妙表达、田间疾病严重程度的空间分布以及木薯田本身的小尺寸和复杂结构有关。© 2017 作者。Pest Management Science 由 John Wiley & Sons Ltd 代表化学工业协会出版。
