Protect onions from downy mildew

Downy mildew is called a water mould for a reason – it likes long dew periods, leaf wetness, rainfall and cool temperatures (< 22°C). Remember to check the temperature in the canopy as irrigation can create a micro-climate in your field.

In a normal year, August – with its cool nights and low dews – is when we tend to see more downy mildew alerts.

But it seems we don’t even know what’s normal anymore; this year, downy mildew season started in July for some parts of Canada. In the Holland Marsh, for example, we are well into several sporulation-infection periods.

So, what’s the right tool to protect your onions?

There are several options, and the choice depends on what you need.

• Ridomil Gold^® MZ is a systemic and contact fungicide. Research at the Muck Station in Ontario consistently ranks Ridomil Gold MZ among the most effective products for downy mildew control.
• Revus^® is a translaminar fungicide. This means it protects all parts of the treated leaf, for five to seven days.
• Orondis^® Ultra is a systemic fungicide. Orondis Ultra moves into new growth and provides long-lasting control. It’s also highly ranked in the Muck Station research trials.

Which products require a surfactant?

Onions stand upright and are waxy. They offer both a tricky target to hit and a tricky surface to stick to. As a result, surfactants are sometimes – but not always – recommended.

Always read and follow label directions. Orondis^®, Ridomil Gold^®, Revus^® and the Syngenta logo are trademarks of a Syngenta Group Company © 2022 Syngenta.