Strategies to Stay Ahead of Spring Diseases

While spring is one of the busiest times of year, it is also an essential time to watch for disease pressure that can build with increasing temperatures.

As production continues, consider the following strategies:

  • Employ proven cultural practices, like maintaining a clean growing environment and properly managing irrigation timing
  • Recognize the initial signs of disease by scouting early and often to quickly identify problems and remove infected plants
  • Develop a disease management program that rotates effective fungicide products, including unique combination products like Postiva fungicide

Common diseases encountered during spring production include:


Botrytis, or gray mold, is the most common disease that affects ornamental plants and thrives in cool, humid environments. It is especially threatening during spring production and when plants are being prepared for storage and shipping. Initial signs of Botrytis include small, water-soaked spots on foliage and flowers. When scouting for Botrytis, look for symptoms such as small, light brown spots or tiny flecks on flowers and V-shaped, tan-brown lesions on foliage. Gray, fuzzy sporulation on infected tissue is a sign of an active infection.

Leaf Spots

Look for leaf spot diseases in later spring months as warmer temperatures, coupled with rainfall and nightly dew, provide the perfect conditions for fungal spore germination. Leaf spots can be caused by many different fungal pathogens including Alternaria spp., Cercospora spp. and Colletotrichum spp., as well as bacterial pathogens such as Xanthomonas spp. and Pseudomonas spp. Inspect the lower and interior canopy of plants for spots as they may initially develop there because of wet foliage, reduced air movement and higher relative humidity. Fungal leaf spots tend to be more rounded in appearance, with distinct margins and a colored border. Bacterial leaf spots initially appear as water-soaked spots that are more angular in appearance.

Powdery Mildew

Many bedding plants and perennials are susceptible to powdery mildew pathogens. This disease first appears as white, talcum-like spots called “colonies” on leaves, stems and flowers. The colonies grow to cover the plant’s surface and can cause leaves to turn yellow, brown and then drop if uncontrolled. Sometimes, such as in Calibrachoa, sporulation is sparse and infections occur in the lower canopy causing leaf collapse.

Preparing for potential diseases can help you avoid crop damage and ensure high plant quality through the end of the season. Cultural practices and scouting alone are sometimes not enough to control diseases so preventive applications are necessary for the best protection.

Long-lasting Protection with Postiva

Postiva, the latest addition to the Syngenta fungicide portfolio, provides broad-spectrum, long-lasting control of various diseases that are common in the spring like Botrytis, powdery mildew and leaf spots, including bacterial disease suppression.

Powdery mildew on Calibrachoa. Rechcigl, Syngenta

Postiva is powered by ADEPIDYN® technology, a succinate dehydrogenase inhibitor (SDHI), in FRAC group 7 and difenoconazole, a DMI (demethylation inhibitor) fungicide in FRAC group 3, which is a combination unique to the ornamental market. With two modes of action, Postiva offers a strong defense against multiple pathogens, while helping delay the development of resistance when used in rotation with other trusted products, such as Mural®, Palladium® or Daconil® brand fungicides. Once applied, Postiva quickly moves from the leaf surface into the waxy layer which creates a reliable, rainfast barrier of protection.

A final spray application of 14-16 fl. oz./100 gal. of Postiva in the second to last week of production helps you protect plants against Botrytis and finish strong. 

Learn more about Postiva here, or download any of our proven agronomic programs to learn how to best incorporate Postiva into your management program.

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

© 2023 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. ADEPIDYN®, Daconil®, Mural®, Palladium®, Postiva, and the Syngenta logo are trademarks of a Syngenta Group Company.

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