Department of Entomology, University of California, Riverside 92521 and Department of Environmental Science, Policy and Management, University of California, Berkeley 94720.
Phytopathology. 2019 Feb;109(2):277-285. doi: 10.1094/PHYTO-07-18-0217-FI. Epub 2019 Jan 7.
For vector-borne plant pathogens, disease epidemics may be attributable to multiple mechanisms, including introduction of a novel vector whose epidemiological role differs from that of native vectors. In such cases, understanding an exotic vector's ability to drive an epidemic is central to mitigating its impact. We studied how the invasive glassy-winged sharpshooter (Homalodisca vitripennis Germar) can drive Pierce's disease outbreaks in vineyards, focusing on its potential to promote vine-to-vine (i.e., secondary) spread of Xylella fastidiosa relative to potential constraints stemming from seasonality in the pathosystem. First, we developed a general vector-borne disease model to understand the consequences for disease dynamics of (i) seasonal acquisition efficiency and (ii) seasonal host recovery from infection. Results of the modeling indicate that these two sources of seasonality could constrain disease incidence, particularly when working in concert. Next, we established a field cage experiment to determine whether H. vitripennis promotes vine-to-vine spread, and looked for evidence of seasonality in spread. Broadly, results from the experiment supported assumptions of the model; there was modest to significant increase in the frequency of pathogen spread over the first season, and those new infections that occurred later in the season were more likely to recover during winter. Ultimately, by the end of the second season, there was not evidence of significant secondary spread, likely due to a combination of seasonal constraints and low transmission efficiency by H. vitripennis. Collectively, these results suggest that, although H. vitripennis may be able to promote vine-to-vine spread in certain contexts, it may not be the key factor explaining its impact. Rather, the ability of H. vitripennis to drive epidemics is likely to be more directly related to its potential to reach higher population densities than native vectors.
对于以媒介传播的植物病原体而言，疾病的爆发可能归因于多种机制，包括引入一种新型媒介，其流行病学作用与本地媒介不同。在这种情况下，了解外来媒介传播疾病的能力对于减轻其影响至关重要。我们研究了入侵性的玻璃叶蝉（Homalodisca vitripennis Germar）如何在葡萄园引发皮尔斯氏病的爆发，重点研究了它相对于该病原体系统季节性限制，促进韧皮部杆菌（Xylella fastidiosa）在葡萄藤之间（即二次）传播的潜力。首先，我们开发了一个通用的媒介传播疾病模型，以了解（i）季节性获取效率和（ii）感染后季节性宿主恢复对疾病动态的影响。模型结果表明，这两个季节性来源可能会限制疾病的发病率，特别是当它们协同作用时。接下来，我们建立了一个野外笼实验来确定玻璃叶蝉是否促进了葡萄藤之间的传播，并寻找传播季节性的证据。总的来说，实验结果支持了模型的假设；在第一个季节中，病原体传播的频率有适度到显著的增加，而且在季节后期发生的新感染在冬季更有可能恢复。最终，到第二个季节结束时，没有证据表明有显著的二次传播，这可能是由于季节性限制和玻璃叶蝉低传播效率的综合作用。总之，这些结果表明，尽管玻璃叶蝉在某些情况下可能能够促进葡萄藤之间的传播，但它可能不是解释其影响的关键因素。相反，玻璃叶蝉传播疾病的能力可能更直接与其达到比本地媒介更高种群密度的潜力有关。
