Pestalotiopsis disseminata

The life cycle involves the formation of pycnidia or acervuli within the host tissue, which serve as the primary source of inoculum. This pathogen is known for its opportunistic nature, often surviving as an endophyte or saprophyte before becoming pathogenic when the host plant is stressed by environmental factors or mechanical injury.

This fungus exhibits a wide host range, infecting various ornamental plants, palm trees, conifers, and horticultural crops. It is particularly problematic in nursery settings and landscapes where high humidity persists. The pathogen colonizes various parts of the host, including leaves, stems, twigs, and fruits, leading to significant degradation of plant tissue.

Damage is characterized by the breakdown of cellular structures, which interferes with nutrient transport and photosynthesis. In nurseries, it can cause rapid decline in the health of young seedlings, leading to high mortality rates if not managed promptly. It is considered an economically significant pathogen in both nursery and agricultural production.

The primary symptom of infection is the development of necrotic lesions or leaf spots. These spots may be circular or irregular in shape and often vary in color from pale grey to dark brown or black. A distinct border often separates the diseased tissue from the healthy green parts of the leaf or stem.

As the disease progresses, small, raised black structures, which are the fruiting bodies of the fungus, appear on the surface of the lesions. Under moist conditions, these structures release spores that can be spread by splashing water or air currents. In severe cases, the infected foliage drops prematurely, and twigs may die back, leading to permanent damage.

Management of P. disseminata requires an integrated approach focusing on cultural practices and chemical intervention. Proper sanitation is essential; infected plant debris must be removed and destroyed to reduce the primary inoculum load. Improving air circulation around plants and avoiding overhead irrigation can significantly lower the humidity levels required for spore germination.

Chemical control involves the application of fungicides, specifically those containing active ingredients such as copper, mancozeb, or triazoles. Treatments should be applied preventively, especially during periods of warm, wet weather. It is important to rotate fungicide classes to mitigate the risk of the pathogen developing resistance to specific chemical agents.