Cucumber Cucurbits

Cucurbit Downy Mildew Update – June 14, 2023

by Katie Goldenhar and Elaine Roddy

To date, the 2023 cucurbit downy mildew situation is looking remarkably similar to what we experienced in 2022.

Cucurbit downy mildew has not been identified in Ontario or the Great Lakes region but has been identified in New Jersey on June 13 (in 2022 it was identified by Rutgers on June 11).

Michigan State University annually conducts spore trapping and reports their findings here. Dr. Hausbeck’s lab is reporting the clade associated with each spore detection. Clade 1 infects pumpkins, squash and watermelons and is not a concern most years in Ontario. Clade 2 infects cucumbers and cantaloupe and is seen annually in the region. Clade 2 spores have been identified in Michigan on June 5, 2023 (in 2022, spores were detected on June 2nd).

Ontario growers should be on high alert and scouting often for this disease. Cucumber and muskmelon crops are the most susceptible, especially if there is rainfall, extended dew or heavy overhead irrigation.

For more information about this disease and its control measures, see the article Cucurbit downy mildew – get out and scout!

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