Diagnostic Guide for Cucurbit Downy Mildew

Abstract

Cucurbit downy mildew caused by the oomycete Pseudoperonospora cubensis is the most devastating foliar disease on cultivated cucurbitaceous crops. Failure of host resistance in cucumber and previously effective fungicides has occurred in the last few years in the United States and Europe, making accurate and early diagnosis critical for timely disease management. The objective of this diagnostic guide is to describe the current taxonomy, host, geographic range, symptoms, and signs as well as effective techniques for pathogen identification, evaluation, isolation, and storage for P. cubensis.