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.

Spornado was discussed in this 2017 CPMA Podcast, Produce Talks.

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Spore traps alert growers to late blight pressure.

Determining late blight presence and the resulting pressure on potato crops is an ongoing challenge. Usually, potato growers start a preventive fungicide program with broad spectrum fungicides before row closure, which ensures stems and leaves at the base of plants are protected from both early and late blight. If late blight is identified in the field, growers switch to fungicides that specifically target it for enhanced crop protection.

But what if it could be determined in advance if late blight will be a problem? Time and money could be saved.