The last few years, cucurbit downy mildew has appeared earlier and earlier in some regions. Downy mildew has already been detected in Ontario and the neighbouring US states.

With the transplants recovering from shock and starting to push out new leaves, let’s get a head start on downy mildew.

New fungicide option for 2022

Allegro^® fungicide is now registered on the entire cucurbit crop group for downy mildew suppression at the low rate and control at the high rate.

• Include Allegro early in the crop to incorporate a different FRAC group into the rotation.
• Allegro contains a Group 29 fungicide, fluazinam. No other downy mildew fungicide is a Group 29.
• Fluazinam is a contact fungicide, which means proper, thorough coverage is key.

What to do now?

OMAFRA has published guidelines for when to spray and what to spray for downy mildew in cucumbers. Remember: Preventive applications always work best and reduce the risk for developing resistance.

There are a handful of effective tools for downy mildew in cucurbits:

Crop	Product	L/acre	Resistance risk	No. of applications	REI (hours)	PHI (days)
Cucurbit vegetables		0.35 to 0.7	low	3	24	30
		1.94	low	2	12	2
		0.16 to 0.24	high	See below	12	0

Re-entry interval (REI), Pre-harvest interval (PHI)

Use Orondis^® Ultra fungicide in no more than 33 percent of the applications, or a maximum of four applications, whichever is fewer.

Always read and follow label directions. Bravo^®, Orondis^® and the Syngenta logo are trademarks of a Syngenta Group Company. Allegro^® is a trademark of ISK Biosciences.