Understanding and Combating Sclerotinia Stem Rot in Tomatoes

Have you ever heard of timber rot, white mold, or sclerotinia stem rot? These are all names for a destructive disease that can wreak havoc on tomato plants, particularly in cold, wet climates. Identified as Sclerotinia sclerotiorum, this fungal pathogen can persist in the soil for up to 10 years and infect over 400 plant species, including important crops like potatoes and peppers.

In this article, we will delve into the world of sclerotinia stem rot, exploring its symptoms, favorable weather conditions for infection, disease cycle, and methods to manage and prevent its spread in your garden. By the end of this comprehensive guide, you will be equipped with the knowledge needed to identify, treat, and protect your tomato plants from this insidious disease.

What You’ll Learn

Let’s begin by outlining the key information you will gain from this article:

• Sclerotinia Stem Rot Symptoms
• Favorable Weather for Infection
• The Disease Cycle
• How Your Garden Can Become Infested with Timber Rot
• How to Manage Sclerotinia of Tomato

Sclerotinia Stem Rot Symptoms

A distinguishing characteristic of sclerotinia stem rot is the formation of structures known as sclerotia, resembling small, black, hard, cylindrical objects resembling rat droppings. These survival structures can be found inside tomato tissue that has turned white and dry due to the disease, giving it the alternate name of timber rot.

The initial signs of infection typically appear at the base of the main stem or on lower branches as watery soft rots and bleached areas on leaf axils and stems. A white fuzzy mold then grows both inside and outside the plant, spreading to flowers, petioles, leaves, and stems. Infected fruit may turn gray and rot as the disease progresses, ultimately causing the plant to wilt.

Favorable Weather for Infection

White mold thrives in cool, wet conditions with temperatures between 59 to 70°F, particularly favoring night temperatures around 60°F. Spores are most likely to infect tomato plants after prolonged wetness with a relative humidity above 90 percent, making blooming plants particularly susceptible to infection.

The Disease Cycle

In warm, dry environments, sclerotia can remain dormant in the soil for extended periods until conditions are conducive for germination. Once activated, the fungus produces fruiting bodies that release sticky spores capable of infecting susceptible plant tissue. After completing its disease cycle, the pathogen remains dormant until favorable conditions recur, although sclerotia persist in the soil, posing a threat to future plants.

How Your Garden Can Become Infested with Timber Rot

Sclerotinia stem rot spreads through airborne spores, contaminated soil, or infected debris blown into your garden. Weeds can also serve as hosts for the pathogen, contributing to its persistence and spread. Proper sanitation practices and weed management are essential to prevent the disease from infiltrating your garden.

How to Manage Sclerotinia of Tomato

Here are some effective strategies to minimize infection and combat timber rot in your tomato plants:

Cultural Controls

• Rotate crops and avoid planting in contaminated soil.
• Inspect plants regularly and remove infected ones.
• Eliminate weeds to reduce pathogen reservoirs.
• Maintain good drainage and avoid overwatering.
• Prune plants for improved air circulation.
• Avoid overhead watering to prevent foliage moisture.

Biofungicides

• Consider using biofungicides containing fungi that parasitize the sclerotia.
• Integrate biofungicides into an overall pest management system.

Fungicides

• Utilize synthetic fungicides labeled for S. sclerotiorum control.
• Options include Endura, Fontelis, and Botran.

By implementing these cultural, biological, and chemical controls, you can effectively manage and prevent the spread of sclerotinia stem rot in your tomato garden.

The Combination of Spores and Sclerotia Is Deadly

White mold poses a significant threat to tomato plants through airborne spores and soil-borne sclerotia. Early recognition of symptoms and proactive management practices are vital to combating this disease effectively.

Engaging in preventive measures, such as sanitation, cultural controls, and the use of biofungicides and fungicides, can help you protect your tomato plants from the devastating effects of timber rot.

If you have encountered timber rot in your garden, share your experiences in the comments to help others learn from your challenges and successes.

For more guidance on identifying and treating common tomato diseases, explore our additional articles on blossom-end rot, early blight, septoria leaf spot, and southern blight.

With this comprehensive understanding of sclerotinia stem rot and its management strategies, you are now ready to safeguard your tomato plants from this formidable foe and ensure a thriving harvest in your garden.