From Meg McGrath, Long Island Horticultural Research & Extension Center, mtm3@cornell.edu:
Cantaloupe as well as cucumber are now being affected by downy mildew in the Northeast. Symptoms recently were found on cantaloupe on Long Island and in Rhode Island and Massachusetts.
Downy mildew typically starts to develop on cantaloupe at least a week later, often longer, than cucumber in an area. The same pathogen type ‘clade’ affects these two cucurbit types (Clade 2). A different clade affects squashes, pumpkin, and watermelon (Clade 1). It occurs in the northeast more sporadically and moves through the eastern U.S. later in the growing season than Clade 2. Downy mildew has been seen on pumpkin and squash only as far north as Kentucky and North Carolina so far this season.
To determine when fungicide application is warranted:
- use the filter for the cucurbit downy mildew occurrence map to know where downy mildew has been seen on the crops you are growing.
- monitor forecasts for risks of successful pathogen spread to your crop from affected crops. Past as well as current forecasts are available.
- at least once a week look for symptoms.
See previous updates and the cucurbit downy mildew webpage for additional information and photographs of symptoms on all cucurbits.
Please report when seen to your extension specialist or at the forecast website. Knowledge of where downy mildew is occurring is critical to the success of forecasting.