From Meg McGrath, Long Island Horticultural Research & Extension Center, mtm3@cornell.edu:
On July 14 new-appearing symptoms were found in a commercial planting of cucumber on the North Fork of Long Island. This is the earliest this disease has been found on Long Island since monitoring started in 2007, but it is not surprising because symptoms were observed early this season in the mid-Atlantic region (the most likely source of the pathogen for Long Island), and 6 days beforehand was the first high risk forecast for Long Island at the CDM.ipmpipe.org website. Previous first observations on Long Island ranged from July 16 to September 7.
Presently cucumber crops are most at risk for becoming infected. Cantaloupe typically are affected next. The cucurbit downy mildew occurrence map has a new filter feature to view confirmed cases for a select cucurbit crop type as well as all occurrences.
See cucurbit downy mildew webpage for information about management in conventional and organic crops.
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.