Causes of Velvet Spot Disease

Velvet blotch is caused by the fungus Cladosporium fulvum. This fungus thrives particularly well in warm and humid environments, making it a common threat in greenhouses and during the humid summer months. The spores of the fungus spread through wind, water and also through direct contact with infected plants.

The fungus enters the leaves through the stomata and begins to multiply there. High humidity and dense planting promote the spread of the disease because they encourage the formation of water droplets on the leaves, which in turn promote the germination of the fungal spores.

Symptoms of Velvet Spot Disease

The first signs of infection are pale green to yellowish spots on the upper surface of the leaves. These spots may grow larger over time and turn into brown or olive green velvet spots, which give the disease its name. This velvety appearance is caused by the spore masses of the fungus on the underside of the leaves.

In advanced stages of the disease, leaf necrosis (dying processes of plant tissue) can occur, in which the affected leaves die and fall off. This leaf loss weakens the plant considerably, as photosynthesis performance is reduced, which leads to a lower fruit yield. The fruits themselves can also show spots in severe cases.

control strategies

Controlling velvet blotch requires a comprehensive approach that includes both preventive measures and direct control methods:

1. variety selection
   Growing resistant tomato varieties is one of the most effective methods of prevention. There are now many varieties that have been specifically bred to combat Cladosporium fulvum.

2. Optimal climate
   Reducing the humidity in greenhouses through regular ventilation and the use of fans can inhibit the spread of the fungus. Care should also be taken to ensure that the plants are sufficiently spaced apart to ensure good air circulation.

3. garden hygiene
   Removing and destroying infected leaves and plant debris is crucial to preventing the spread of the disease. Regularly cleaning gardening tools can also help prevent transmission of spores.

4. fungicides
   The targeted use of fungicides can help control the spread of the disease. It is important to alternate fungicide use to prevent the fungus from developing resistance. However, before using chemical agents, an accurate diagnosis should always be made to ensure that it is actually velvet spot disease.

5. crop rotation and site selection
   A frequent change of cultivation area and a diverse crop rotation can help to reduce the spore load in the soil. Tomatoes should not be grown in the same location for several years in a row.