As of Wednesday, September 1st, cucurbit downy mildew has been found in Annapolis, Kings, and Hants Counties. While all Cucurbits are susceptible to downy mildew, there are different Clades which affect different subsets of the Cucurbit Family. Clade I predominantly infects watermelon, pumpkin, squash, and zucchini. Clade II predominantly infects cucumbers and cantaloupes. So far, we have only found downy mildew in cucumber fields, suggesting that we have Clade II.
Downy mildew spores blow in on storm systems from the United States, so it is possible that Thursday's storm will bring in Clade I, so growers should be aware. Downy mildew cannot overwinter in Nova Scotia unless the infection spreads to greenhouses. Please reach out to Rosalie Gillis-Madden, Perennia’s Vegetable Specialist by email or cell (902-670-9655) if you want support around managing this disease. This late in the season, growers of squash and pumpkins might choose not to put on a protectant spray.
- Growers who do not yet have downy in their fields and are hoping to continue picking their cucumbers and cantaloupes are advised to put on a protectant spray (i.e. Zampro or Torrent for conventional growers, Serenade Opti or copper for organic growers).
- If you have downy mildew in your cucumber or melon field, and you wish to keep picking, an application of Orondis Ultra is advised (copper for organic growers). Conventional growers should rotate to a different FRAC group and spray again 7 days after the first spray as advised by the pesticide label (suggested Torrent as a second application for conventional growers, and another copper spray for organic growers.) Please also call Rosalie so we can document the spread of this disease.
- If you are hoping to keep picking zucchini and watermelons for a few more weeks, a protectant spray is advised as downy mildew spores from Clade I might blow in on Thursday’s storm (i.e. Zampro or Torrent for conventional growers, Serenade Opti or copper for organic growers). You should rotate to a different FRAC group and spray again 7 days after the first spray as advised by the pesticide label.
- If you find downy in your squash, pumpkins, watermelons, or zucchini, please contact Rosalie right away.
Please note that powdery mildew sprays ARE NOT effective against downy mildew. Downy mildew can very quickly breed fungicide resistance so rotating FRAC groups and following the label closely is key to management.
If you are currently picking crop, please pay close attention to the PHI listed on the fungicide label.
If you are not currently subscribed to the Nova Scotia Vegetable Blog, please click here to subscribe to receive an email every time there is a post.
