Shot hole Disease
Shot hole is caused by the fungal pathogen Wilsonmyces carpophilu (Coryneum blight).
Most severe on apricots, but occurrs on all stone fruit. The fungus infects the leaves, twigs and fruits.
Infected leaves show small brown spots with reddish margins (about 1 mm diameter), these spots expand to larger circular lesions (about 3mm diameter). These spots dry and fall out of the leaf, giving a shothole appearance. The infected twigs show clear- cut brown margins with a negrotic center, which does not drop out, but ooze large amounts of gum. Further on lignification of infected twings is hindered and the lesions will grow into cankers. In severe cases premature defoliation of the tree may result.
Fruits show firstly small circular, deep purple spots. As the disease progresses, the symptoms differ according to fruit type. On apricots the spots become brown, raised and rough, giving the fruit a scabby surface. On peaches and nectarines the scabs develop into deep indentations.
Infected fruit have spots of gum and in severe cases cracks in the skin.
The shothole fungus survives in infected buds. It is able to infect leaves, stems and fruits during cold, rainy weather periodes in spring and autumn. Rain periodes to infect healthy plant organs are needed.
The fungus is able to persist several years in the cankers or buds of infected twigs. Whenever conditions are favourable it may continue to grow, even during winter time. In spring time the conidia are splashed by raind to flowers and young leaves and infect them. In unfavourable periodes (dry conditions) the conidia are still viable for several months. Rain is necessary for dispersal and humid conditions are needed for germination. The fungus is able to grow above 2°C.
Adaskaveg JE, Ogawa JM, Butler EE (1990) Morphology and ontogeny of conidia in Wilsonomyces carpophilus, gen. nov., and comb. nov., causal
pathogen of shot hole disease of Prunusspecies. Mycotaxon 37, 275–290.
Ashkan M, Asadi P (1971) Shot hole of stone fruits in Iran. Iranian Journal of Plant Pathology 7, 39–63.Esfandiari E (1947) Les maladies des plantes cultivées et des arbres
fruitiers des régions subtropicales du nord de l’Iran. Entomologie et Phytopathologie Appliquées 5, 2.
Grove GG (2002) Influence of temperature and wetness period on infection of cherry and peach foliage by Wilsonomyces carpophilus. Canadian
Journal of Plant Pathology 24, 40–45.
Ogawa JM, Zehr EI, Bird GW, Ritchie DF, Uriu K, Uyemoto JK (1995) Compendium of stone fruit diseases. (The American Phytopathological
Society Press: St Paul, MN)