Rust and leaf spot diseases can drastically affect the appearance of plants, leaving unsightly specks on the anatomy. It’s important for growers to be aware of any early signs of these common ornamental diseases to prevent damage and treat infections. 

Identifying Rust

Rusts are pore-producing fungal pathogens that can damage leaves, stems, flowers and fruits of a wide range of ornamental crops. The most susceptible plants include aster, chrysanthemum, vinca and other perennial crops. Rust diseases are more likely to establish in cool, mild temperatures and moist conditions. While most pathogens causing rust do not typically lead to plant mortality, rust can negatively impact the appearance and marketability of the plants.

Growers should monitor for the following symptoms:

• Pale white chlorotic spots that appear on the upper surface of the leaves
• Raised, blister-like pustules that typically form on the undersides of leaves directly under these spots or on the stems
• Pustules that vary in color from red, orange, brown or creamy white, depending on the pathogen
• Spores that are often the same color as the pustule
  • Confirmation of rust can be made by rubbing the infected leaf across white paper
• Severe infestations resulting in leaf drop

Leaf Spot Signs

Although less common in the cooler months, leaf spots are another sign of disease, especially for ornamental crops in warmer climates. Depending on the causal pathogen, leaf spots can vary in shape and size, but tend to be more rounded in appearance and typically have distinct margins with a colored border.

Prevention Methods

Syngenta offers the following solutions for excellent control of rust and leaf spots:

• Heritage^® fungicide
• Mural^® fungicide
• Postiva^™ fungicide

Heritage, featuring the active ingredient azoxystrobin, is formulated with xylem mobility to evenly transport the active ingredient throughout leaves, stems and roots. This provides long-lasting protection against a wide range of foliar, crown and root-infecting fungi on ornamentals.

Mural offers one versatile solution powered by an advanced generation succinate dehydrogenase inhibitor to control key foliar, stem and root diseases, making it an excellent choice for nursery and greenhouse operations.

Postiva is formulated with two modes of action, offering strong, complete protection and reliable control against fungal and bacterial pathogens.

Learn more about preventing rust and leaf spots at GreenCastOnline.com/Ornamentals.

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© 2024 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. Greencast^®, Heritage^®, Mural^®, Postiva™ and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective third-party owners.