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Downy mildew identified on hemp in southwestern Ontario

September 22, 2020  By Top Crop Manager

Southwestern Ontario’s hemp fields might have a pest problem.

Downy mildew, caused by Pseudoperonospora cannabina, has been identified in several hemp fields in southwestern Ontario. The disease first appeared in early September.

While powdery mildew is a common pest of hemp, downy mildew is not. There have been no reported cases of downy mildew of hemp in Canada before, but cases have been reported in the U.S. in the past.


Spores of downy mildew can travel hundreds of kilometres in the wind. They are produced on the lower leaf surface and appear mostly in the early morning before they are released into the wind.

All hemp growers in the region should watch out for this disease. |READ MORE


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