Updates on Cucurbit downy mildew

Tuesday, August 31, 2021

Monday, August 30th, 2021 downy mildew was found in King's County.  Please read the original blog post here.  Downy mildew that infects Cucurbits is specific to Cucurbits - it won't infect onions, grapes, hops, lettuce, spinach, basil, etc.

There is a great Cucurbit Downy Mildew Diagnostic Key, which might help you determine if you have downy in your field.  Please do not hesitate to reach out if you need support in identification and you are a registered farm in Nova Scotia.

So far, downy mildew has only been confirmed here on cucumbers.  The Nova Scotia Vegetable Blog will be updated if that changes.  There are two different host-specific clades of downy mildew.  Clade I mostly infects watermelon, pumpkin, squash, and zucchini.  Clade II mostly infects cucumbers and cantaloupe.  It is possible that we currently only have Clade I in Nova Scotia.  However, there is a storm system blowing in on Thursday/Friday that will certainly bring downy conducive conditions (i.e. prolonged leaf wetness), and perhaps more infections spores of either Clade I or Clade II.  

Cucumber and melon growers should apply protective fungicides as outlined in yesterday's blog post.  Pumpkin, squash, zucchini, and watermelon growers can take a gamble - either apply a protectant as previously mentioned; do nothing and hope there isn't downy that will infect the pumpkin/squash subset; or harvest early.  For growers that do not have established drive rows in their winter squash and pumpkins - especially if they are close to harvest - it may be worth the risk to wait see and thereby avoiding driving over crop to make a fungicide application.  Harvesting early is a good option if the crop is mature and you have curing facilities, especially in light of the forecasted precipitation coming our way on Thursday/Friday.  Downy mildew does not affect fruit, however in the case of cantaloupes, the fruit will be less sweet.