Diplocarpon mespili

Diplocarpon mespili is a pathogenic fungus within the Ascomycota phylum that causes leaf spot disease, commonly known as Entomosporium leaf spot, affecting a wide range of plants in the Rosaceae family. Systematically, it belongs to the Kingdom Fungi, Class Leotiomycetes, and Order Helotiales. It acts as a specialized plant pathogen that attacks the tissues of leaves, petioles, and fruits.

The primary host plants for this pathogen include hawthorn, quince, medlar, pear, and serviceberry. The disease manifests as numerous small, circular, reddish-brown or black spots on the leaves. Over time, these spots may coalesce, leading to severe chlorosis, leaf curl, and premature defoliation of the affected host plants.

The biology of the pathogen is closely tied to overwintering plant debris. The fungus survives in fallen leaves as mycelium and apothecia. In the spring, when warm and humid conditions arrive, ascospore discharge occurs, and these spores are dispersed by wind and rain splashes onto young, susceptible foliage. Secondary infections throughout the growing season are caused by conidia, which spread rapidly in high-humidity environments.

Infection development is optimal at temperatures ranging from +15°C to +25°C, provided there is free water on the plant surface. Persistent rain, fog, and dense canopy planting facilitate the rapid spread of the disease in orchards and nurseries, which can lead to severe epidemics during years favorable to the fungus.

The damage caused by Diplocarpon mespili stems from the severe weakening of trees due to premature leaf drop. This reduces winter hardiness, slows shoot growth, degrades fruit quality, and causes premature fruit drop. Without appropriate control measures, the fungus can jeopardize the survival of young saplings and significantly reduce the yield of established fruit-bearing trees.

• Sanitation by removing and destroying fallen leaves in autumn.
• Pruning to improve air circulation within the canopy.
• Application of copper-based fungicides during the dormant period.
• Use of systemic fungicides (triazoles, strobilurins) at the first sign of symptoms.
• Maintaining proper spacing during plantation establishment.