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Infection pathways in cucumber downy mildew

Project Code: PRR16-050

Project Lead

Dr. Katerina Jordan - University of Guelph


Assessment of propagative material, alternative downy mildew host plants, and plant residue as inoculum sources for the disease in cucumber production

Cucumber downy mildew, caused by the pathogen Pseudoperonospora cubensis, is a threat to the industry and was identified as a priority pest issue by Pesticide Risk Reduction. Under ideal conditions for disease development, foliage of infected crop may become completely blighted, leading to significant yield losses. Current pest management measures involve a preventative spray program where fungicide applications may be required on a weekly interval over a prolonged period. As the pathogen spreads through airborne spores, disease risk forecasts are based on weather patterns across large geographic regions. The role of local sources of inoculum in spreading the disease is unknown, and the Reduced-risk Strategy for Downy Mildew Management in Cucumber identified this knowledge gap as a priority for action.

This 3-year project starting in summer 2016 focuses on P. cubensis infection pathways as inoculum sources in commercial cucumber production in Canada. Tests to identify potential pathways will include commercial cucurbit seeds, cucurbits grown in nearby fields, greenhouse cucumbers, wild cucurbits, and crop residue of cultivated cucurbits from previous growing seasons. Material collected in fields, greenhouses, uncultivated areas, and from seed suppliers, will be tested in the lab for presence and identification of the pathogen. The results will allow for a better understanding of the spread of the disease and the role of local sources of inoculum which may need to be taken into consideration as components in future disease forecasting.

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