Don’t let Pythium sneak into production

Protecting plants from root and stem rots can always be a challenge, particularly during late fall and winter, when there tends to be more cloudy days and the greenhouse temperatures are cooler. Under these conditions, the growing media tends to stay wet longer, presenting an opportunity for oospores of Pythium spp. to germinate and invade wounds and tender plant tissue. While unrooted cuttings and young seedlings in propagation areas are at risk due to the frequent misting and highly humid environment, established plants are also at risk for losing healthy roots under these conditions. 

Symptoms to watch for include:
  • Collapse of young seedlings at the soil line
  • Lower stems with water-soaked tissue
  • Stunted plants
  • Plants with light green or yellow foliage
  • Damaged roots that are brown and soft 

Preventive Measures

Using proper cultural practices in combination with an effective fungicide rotation program is the most reliable strategy for protecting plants against Pythium spp. Cultural tips include:
  • Clean the benches and growing area of debris and sanitize between crops 
  • Provide appropriate plant spacing to allow for good air movement 
  • Elevate pots in low areas where water may pool 
  • Keeping the humidity low by heating or venting 
  • Immediately remove any diseased plants from the area to limit spread

It is important fungicide programs include a rotation of products with modes of action in different FRAC groups. Some effective options include: 

Subdue Maxx® fungicide, powered by an active ingredient in FRAC Group 4, protects roots and stems against Pythium and Phytophthora spp.. It translocates up into the plant canopy where it controls downy mildew diseases as well.

Mural® fungicide, powered by two active ingredients in FRAC Groups 7+11, is another excellent solution to protect ornamental crops against Pythium spp., as well as other soilborne pathogens such as Rhizoctonia solani. Mural also provides plant health benefits, such as enhanced root development.

Learn more about these products at and

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

©2020 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. Heritage®, Mural®, Subdue Maxx® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective owners.

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