Cucurbits Disease Downy Mildew Fungicides

Cucurbit Downy Mildew Update – June 18, 2014

Over the past week there has been increasing downy mildew activity in the Southern US. There are active infections present in Florida, Georgia, Louisiana, Texas and the Carolinas. Late June is typically when infections start occurring in the Great Lakes basin.

Scout all cucumber fields regularly for signs of downy mildew. Begin a preventative fungicide spray program no later than vine development. Start the spray program earlier if cool wet weather conditions, or strong storm activity persists.

You can follow cucurbit downy mildew activity across North America on the ipmPIPE website:

Broad spectrum preventative fungicides include:

  • mancozeb (Dithane Rainshield, Penncozeb 75DF and Manzate Pro-Stick)
  • chlorothalonil (Bravo 500)

As soon as downy mildew is identified in the Great Lakes region, switch to a targeted downy mildew fungicide. These include:

  • cyazofamid (Ranman 400SC or Torrent 400SC)
  • propamocarb/chlorothalonil (Tattoo C)
  • ametoctradin/dimethomorph (Zampro)
  • Fluopicolide (Presidio)

The new Ontario Vegetable Crop Protection Guide (Publication 838) has a full list of cucurbit fungicides. It is available at the regional OMAF/MRA offices and online at ServiceOntario Publications website at

To order by phone: Contact the ServiceOntario Publications Contact Centre at 1-800-668-9938 or 416-326-5300 or TTY 1-800-268-7095 from 8:30 am to 5:00 pm, Monday to Friday.

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