Shot hole disease

Stigmina carpophila is a significant fungal pathogen, best known as the cause of shot hole disease, also referred to as coryneum blight. It belongs to the phylum Ascomycota and specifically targets stone fruit species. This pathogen is globally distributed and causes substantial economic losses in both commercial orchards and home gardens.

The disease affects all aerial parts of the host plant, including leaves, buds, flowers, fruits, and young twigs. The most characteristic symptom is the formation of small, circular, reddish-brown spots on leaves. As the tissue dies, it detaches from the leaf blade, creating the characteristic "shot hole" appearance. On fruits, the fungus causes small, sunken, purple-rimmed lesions that can lead to fruit deformation.

The biology of the fungus allows it to overwinter as mycelium or conidia within infected twigs, buds, and mummified fruits. Dissemination of the pathogen primarily occurs via splashing rain and wind currents, which transport conidia to susceptible tissues. The development of the disease is highly dependent on environmental conditions, particularly high humidity and moderate temperatures ranging from 15°C to 25°C.

Economic impact is significant due to both direct and indirect damage. Direct damage includes fruit lesions that make them unmarketable. Indirect damage is caused by extensive defoliation, which reduces the plant's photosynthetic capacity, and twig blight, which causes dieback and weakening of the tree. Long-term infection can result in severe tree decline and reduced productivity over successive seasons.

Control of Stigmina carpophila requires an integrated management strategy. Cultural practices, such as removing and destroying infected branches and leaf litter, are essential to reduce the inoculum level. Chemical control is usually achieved through the application of copper-based fungicides during the dormant season and protective or systemic fungicides during the growing season when environmental conditions favor infection.