Cucurbit Downy Mildew Alert


Downy mildew symptoms were reported earlier this week on cucumber crops by growers in Orange and Ulster Counties, NY, and Fairfield County, CT.  This disease also appeared earlier than usual in eastern NY in 2021 which also followed early appearance in NJ.  This early onset was predicted - there were 2 high risk forecasts posted at the Cucurbit Downy Mildew Forecast website for pathogen spread from known occurrences of downy mildew in NJ and PA to these locations. 

 The rain that came through last night has resulted in a high risk forecast for CDM pathogen spread for southeast and east-central NY , northwest CT, western MA, and southern VT. Moderate Risk for Long Island, southeast CT, RI, central and eastern MA. Low Risk for cucurbits in central VT, central and southern NH, southwest ME.  If infection results, expect symptoms to start to appear in 5 days.

 Only cucumber and cantaloupe crops are at risk now.  Producers of these crops should have protectant fungicides for CDM prior to any future storms. These are listed in the New England Vegetable Management Guide - go to the crops tab and select the appropriate cucurbit crop(s). Chlorothalonil or copper products (organic options) are protectant fungicides that most growers probably already have on-hand.

Any conventional grower who was not able to get a protectant spray down prior to last night’s rain and who hasn’t sprayed within past week, and is feeling concerned because they did receive rain – Meg McGrath from Cornell suggests applying a locally systemic fungicide such as Curzate (cymoxanil) today.

Monitor your crops after this system moves through. If you suspect you have CDM infections, please take photos and send them to your local extension specialist. Once CDM occurs in our area it will be important to switch from protectant fungicides to fungicides with specific activity against CDM.

The Extension Fruit & Vegetable team.

Author(s)

Rebecca Sideman
Sustainable Horticulture State Specialist
Full Extension State Spec/Prof
Phone: (603) 862-3203
Office: Cooperative Extension, Kendall Hall, Durham, NH 03824