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This article was published in 2022 and updated in 2024 with new information.

In 2021, Syngenta conducted a monitoring program in onions to understand the prevalence of fungicide resistance in Eastern Canada.

Over 100 samples were sent in from Ontario, Quebec and Nova Scotia, and all fields came back resistant to the QoI (or Group 11) fungicides.

What does this mean?

Quadris Top^® fungicide may no longer be as effective against Stemphylium in your onion fields. Quadris Top can still be included in onion spray program to manage other diseases, like purple blotch.

Which products are left for Stemphylium in onions?

At this point, the only registered alternatives to the Group 11 fungicides are Group 7 fungicides, such as Aprovia^® Top and Miravis^® Duo. Alternatives to the Group 11 fungicides include Group 7 fungicides, such as Miravis^® Duo, Aprovia^® Top, Aprovia^®, and the Group 29 fungicide Allegro^®.

So, what can you do to protect your onions?

• Start your fungicide sprays early (ie. 3-leaf). Most fungicides work best when applied preventively, and this is also best practice for resistance management.
• Use Allegro^® as your first spray if your seed has been treated with a Group 7 fungicide that contains penflufen (Group 7) as best practice for resistance management.
• Follow Allegro with Miravis^® Duo as your first foliar Group 7, and then either Miravis^® Duo, Aprovia^® Top or Aprovia^® as your second Group 7.
• Tank mix single site fungicides with a low-risk fungicide like mancozeb.
• At 0.47 L/acre, Allegro suppresses purple blotch, Botrytis leaf blight, and Stemphylium.
• At 0.4 L/acre, Miravis^® Duo controls purple blotch and suppresses Stemphylium and Botrytis leaf blight.
• At 0.39 L/acre (Aprovia^® Top) or 0.30 L/acre (Aprovia) control purple blotch and suppress Stemphylium.

How does Allegro perform in the Great Lakes Region?

Onion foliage treated in Michigan with Allegro had 47% foliar blight from Stemphylium compared to 86% in the untreated control. N = 2


Source: External data (PDMR 13:V135 MI 2018, PDMR 14:V165 MI 2019). Disease severity (% leaf blight) after six or eight applications is shown, with applications made one a 7 to 10-day interval beginning in late June or early July each year. Trials conducted using Allegro^® formulation branded as Omega^® in the United States.

Manage resistance with the 7 step program

It’s become increasingly difficult to build a spray program and still adhere to the Fungicide Resistance Action Committee (FRAC) guidelines. Here are seven tips to remember when managing foliar disease in onions.

1. Participate in resistance monitoring.
2. Keep the number of sprays from each FRAC group to a minimum.
3. Alternate high-risk fungicides.
4. Know your groups! Find the FRAC code on the product label.
5. Mix it up. Include low-risk fungicides in the tank, like mancozeb.
6. Use alternative disease control methods (integrated disease management).
7. Only apply fungicides when needed.

For more information, visit Syngenta.ca, contact our Customer Interaction Centre at 1-87-SYNGENTA (1-877-964-3682) or follow @SyngentaCanada on social media.
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Performance evaluations are based on internal trials, field observations and/or public information. Data from multiple locations and years should be consulted whenever possible. Individual results may vary depending on local growing, soil and weather conditions. 

Always read and follow label directions. Aprovia^®, Miravis^®, Quadris Top^® and the Syngenta logo are trademarks of a Syngenta Group Company. Allegro^® is a trademark of ISK Biosciences Corporation. Other trademarks are the property of their respective owners.