Cooperative Extension at Highmoor Farm

Cucurbit downy mildew (CDM) confirmed in Franklin County, MA

Cucurbit downy mildew (CDM) symptoms were confirmed on Friday, July 25th in Franklin County, MA.

All cucurbits are susceptible to this disease, with cucumbers and melons most at risk. So far this season there are no nearby outbreaks affecting pumpkins or squash. If you have not added DM-targeted fungicides to your spray program already you should do so now for cucumbers and melons. These include:

• Elumin + chlorothalonil or mancozeb
  (FRAC 22): 12-hour REI and 2-day PHI
• Omega (Orbus) + chlorothalonil or mancozeb
  (FRAC 29): 12-hour REI and 30-day PHI for melons and 7-day REI for cucumbers and squash.
• *Orondis Opti (chlorothalonil is part of the premix, additional chlorothalonil is suggested; see label for maximum chlorothalonil rates).
  (FRAC 49 + M05): 12-hour REI and 0-day PHI
• Previcur Flex + chlorothalonil or mancozeb
  (FRAC 28): 12-hour REI and 2-day PHI. Can be applied foliar or via drip chemigation.
• *Ranman + chlorothalonil or mancozeb
  (FRAC 21): 12-hour REI and 0-day PHI in the field and 1-day PHI in the greenhouse.
• Zampro + chlorothalonil or mancozeb.
  (FRAC 40 + 45): 12-hour REI and 0-day PHI

*Products considered to be especially effective in Michigan based on yearly, season-long field trials.*

Tank mix targeted fungicides with protectants and rotate FRAC groups to prevent resistance development. The following fungicides are no longer recommended because of known resistance: Presidio (43), Revus and Forum (40).

For more details see this recent Veg Notes article on cucurbit downy mildew from the UMass Extension Vegetable Program.

University of Massachusetts: Fact Sheet on Cucurbit Downy Mildew

New England Vegetable Management Guide: Cucurbit Downy Mildew chemical management