Late blight is a never-ending potato disease challenge for growers. A preventative fungicide program that includes broad-spectrum fungicides combined with timely sprays of late blight-specific products greatly reduces the chances of late blight epidemics.                                               

A two-year research project (2016-17) was conducted in Ontario to determine if passive spore traps would provide an early warning of late blight to better time late blight-specific fungicides.

The results indicated that passive spore traps placed in commercial potato fields proved to be a reliable method for detecting spores of the late blight pathogen (Phytophthora infestans) at least 15 days before lesions were detected in the field. The traps do not need a source of energy; they are activated by the wind. Filters held in the spore traps retain spores blowing in the air. The filters are changed twice a week and sent to a laboratory where a PCR-based test is used to detect P. infestans DNA. A positive PCR test indicates the presence of spores in the area. This information alerts growers of the increased risk of late blight and the need to tank-mix late blight-specific fungicides with broad-spectrum fungicides.

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