Tips to protect leafy greens
August 11, 2022
We are in the middle of the summer crop of brassica vegetables and lettuces. Whether you are experiencing heat, thunderstorms, cool nights or “normal” weather, check out the sections below to find out what to look for and what to try.
Brassica vegetables
What conditions? What disease?
| Typical host | Disease/pest | Ideal temperature | Humidity | Dew or leaf wetness? | Rainfall? |
|---|
Cabbage, broccoli, brussels sprouts & cauliflower | Alternaria | 15 to 25°C | High | Loves it | Loves it |
Leafy brassica & broccoli | Downy mildew | 10 to 15°C | High | Loves it | Loves it |
What to try when?
| Crop stage | Targets | What to try?* | L/acre |
|---|
Vegetative growth | Alternaria | 
| 0.29 to 0.4 |
Downy mildew | 
| 0.16 to 0.24 |
Head or bud initiation | Alternaria | 
| 0.29 to 0.4 |
Downy mildew | 
| 0.24 |
Head fill | Alternaria, downy mildew | 
| 1 to 1.94 |
Maturity | Alternaria |
| 0.29 to 0.4 |
*Not all products are registered on all Brassica species. Always consult the product label to confirm the application rate and targets by crop.
Emergency use for Switch®
The PMRA recently granted an emergency use for Switch 62.5WG fungicide in brussels sprouts, broccoli and cauliflower to suppress Alternaria leaf blight.
The emergency use is permitted in Ontario, Quebec, Nova Scotia, Prince Edward Island and Newfoundland and Labrador from July 8, 2022 to July 7, 2023.
Applied at 313 to 395 g/acre, include Switch in your spray program to help protect the buds, curds and heads from Alternaria.
What about the bugs?
Flea beetle feeding is killer for leafy brassica whereas caterpillars will take down your cole crops. What is the right tool to choose?
- Matador® insecticide is for knockdown of swede midge, caterpillars and flea beetles in cole crops, gai lon, napa cabbage and gai choy.
- Voliam Xpress® insecticide is for when you want both knockdown and residual activity for caterpillars in cole crops, gai lon, napa cabbage and gai choy.
Leafy vegetables
What conditions? What disease?
During August, watch out for misty mornings, long dew periods and cool morning temperatures. These conditions are ideal for downy mildew.
What to try?
Several tools are available, and prevention is typically best when it comes to downy mildew. The choice depends on what you need:
| Crop | Product | Product/acre | PHI | What does it do? |
|---|
Head lettuce | 
| 1 kg | 14 days | Long-lasting control |
Spinach | 
| 0.46 L | 7 days | Preserves quality |
Leafy vegetables |
| 0.16 to 0.24 L | 1 day | Protects both sides of the leaf |
Leafy greens |
| 0.24 L | 1 day | Protects new growth |
When planning your downy mildew program, keep in mind that as a result of the PMRA re-evaluation of mancozeb, 2022 is the last season allowing use of Ridomil® Gold MZ in lettuce.
Always read and follow label directions. Bravo®, Matador®, Miravis®, Orondis®, Quadris®, Quadris Top®, Revus®, Ridomil Gold®, Switch®, Voliam Xpress® and the Syngenta logo are trademarks of a Syngenta Group Company. © 2022 Syngenta.
