Early diagnostics of Erysiphe corylacearum causing emerging powdery mildew on hazelnut

Abstract

Erysiphe corylacearum has recently emerged as the causal agent of a new and dangerous powdery mildew affecting hazelnut in northern Italy and other European regions. After shifting to hazelnut as a new host in Asia, the fungus rapidly spread to several European countries within a few years. Compared to the common hazelnut powdery mildew caused by Phyllactinia guttata, this pathogen poses a greater threat due to its substantial impact on yield and hazelnut quality. The disease’s emergence in Italy revealed distinct E. corylacearum subgroupings, population expansion, and high genetic similarity with recently identified isolates from other regions. Effective containment requires early and reliable detection, ideally before symptom onset. In this study, we evaluated innovative, field-deployable diagnostic methods, including isothermal amplification, NIRS / Raman spectroscopic analyses, and foliar pH measurement. These techniques, integrated with portable devices capable of cloud data storage and mobile phone-based remote monitoring, enabled rapid, non-destructive detection of the disease within 30 minutes directly in the field. Both isothermal amplification and spectroscopy-based approaches showed high accuracy in distinguishing between asymptomatic and symptomatic plants before visible symptoms appeared. Our findings suggest that these methods, through measurements of amplification curves or spectral patterns, offer a promising basis for non-destructive diagnosis of emerging hazelnut powdery mildew and potentially other plant diseases. The portability and ease of use of these systems allow their application directly by farmers, without the need for laboratory expertise, making them highly useful in supporting timely disease control.