Defeating Impatiens Downy Mildew

Downy mildew is one of the most common, and costly, diseases to affect impatiens walleriana in greenhouse operations. The pathogen is sometimes mistaken for other issues, including foliar spray injury or nutritional imbalance, so it is important to know which symptoms to watch for when scouting. Signs of impatiens downy mildew infection include:

  • Leaf discoloration or spotting, often within the veins
  • Distorted, wilting or downward curling of the leaves
  • Stunting of plant growth/malformation of leaves and flower buds
  • White or light gray/purple fuzz on the undersides of leaves

A close up of a flowerDescription automatically generated with low confidence

Downy mildew on impatiens
Nancy Rechcigl, Syngenta photo.

Once you have properly identified the disease, remove affected plants immediately to limit spore production and spread. Establishing a rotation program that features products with different modes of action will help prevent future infections and delay resistance development.  

Follow a rotation program that uses a “systemic sandwich” approach. Apply systemic fungicides as a drench at transplant or at the beginning of production and again prior to shipping. Other fungicides with translaminar activity should be applied as sprays in between. The use of systemic products provides extended protection through shipping, and the sprays between the drenches are part of a resistance management strategy to take the pressure off the control provided by the drench.

Segovis® fungicide is a trusted solution for impatiens downy mildew. Featuring a unique active ingredient in FRAC Group 49, Segovis makes an excellent rotation partner for a diversified program. Plus, with low use rates and long-lasting protection, it can help reduce labor costs with fewer hours spent re-applying. A final drench application of Segovis before impatiens leave the greenhouse helps to maintain high-quality crops in the landscape due to its long residual activity.


Control of Downy Mildew (Plasmopara obducens) on Impatiens

Chart, histogramDescription automatically generated

2014 – Vero Beach Research Center, FL

Impatiens treated

Untreated Impatiens

 Impatiens treated

Impatiens treated with 1 fl. oz. drench Segovis

2018 – Krasnow, Vero Beach Research Station, Syngenta


Learn how Segovis can help you defeat impatiens downy mildew and download the impatiens agronomic program today.


Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations. Trials reflect treatment rates commonly recommended in the marketplace.

All photos are the property of Syngenta or are used with permission.

© 2022 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. Micora®, Segovis® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective owners.

Want to receive articles like this in your inbox each month?

Sign-up now to get tips and new product information to stay ahead of the game with Syngenta.

* Indicates required field

Email Subscriptions