Shot-hole disease on Prunus persica – the morphology and biology of Stigmina carpophila

Abstract

Shot-hole disease caused by Stigmina carpophila (Deuteromycetes) is a major limiting factor in peach production, causing foliage shot hole in spring and early summer; fruit-spotting and cankers on limbs and twigs during autumn rains. The fungus overwinters, for at least two seasons, in cankers and killed buds. During spring and summer of 2009–2010, there occurred optimal conditions for manifestation of these symptoms on peach leaves and for the fungus activation. In such humid conditions is activated germination of brown, smooth walled, fusiform conidia with truncate base and rounded apex 16 to 20 μm by 8–10 μm in size, which accounts for the winter infection of buds. The fungus Stigmina carpophila isolated from damaged leaves of Prunus persica formed
in culture sub-hyaline, septate and smooth walled mycelium, and dark brown stromata, partly superficial and partly immersed. The evaluation of mycelium growth suggested a significant effect of cultivation media on the assessed mycelium size on each of the eight days of the experiment. Since the third cultivation day, the size of mycelium on CzD was significantly smaller than the mycelium size on PDA and V-8. The variability of mycelium size on all media decreased with the time of cultivation. There was observed formation of terminal, intercalary, often chained chlamydospores on PDA in the dark. The most serious aspect of shot hole disease on peach is leaf
infection leading to defoliation, as severe defoliation during the early fruit development can cause falling young fruits, and repeated defoliation weakens the trees and reduces their yield.