Nothophoma leaf spot

Nothophoma leaf spot is a fungal disease caused by the pathogen Nothophoma anigozanthi. This specific fungus primarily affects plants belonging to the Anigozanthos genus, commonly known as Kangaroo Paw. As a plant pathogen, it targets the aerial parts of the host, leading to significant physiological stress and aesthetic degradation.

The host range is predominantly limited to Anigozanthos species. The fungus infects leaves, stems, and inflorescences. Because these plants are primarily grown for their unique floral display, the impact of Nothophoma anigozanthi is severe in commercial ornamental horticulture, often rendering the crop unsalable due to extensive necrotic lesions.

Symptoms initially appear as small, chlorotic spots that rapidly expand into larger, dark brown or grey necrotic lesions. Often, these spots are surrounded by a yellowish chlorotic halo. As the infection progresses, the lesions may coalesce, leading to premature leaf senescence, tissue blight, and in severe cases, the collapse of the flower stalk.

The development of the disease is heavily favored by cool to moderate temperatures and high humidity levels. The presence of free moisture on the foliage is essential for spore germination and infection. In greenhouse environments, poor airflow and overhead irrigation are the primary drivers for the rapid spread of the fungus throughout a plant block.

Management of the disease requires an integrated approach. Essential strategies include:

• Maintaining optimal ventilation to reduce humidity levels.
• Avoiding overhead watering to keep foliage dry.
• Strict sanitation protocols, including the removal of infected debris.
• Applying systemic or contact fungicides labeled for leaf spot control.
• Ensuring healthy plant stock through careful scouting and quarantine.