Sites and Structures for the Survival of Colletotrichum spp., the Causal Agent of Bitter Rot of Apple

Abstract

The bitter fruit rot caused by species of Colletotrichum is one of the most destructive diseases affecting apple fruit in humid climates. In Uruguay, when hot and rainy summers occur, they cause important fruit losses. After harvest, Colletotrichum spp. have to survive to guarantee their presence in the next production season. Knowing exactly how this pathogen survives, will allow designing management strategies to reduce the amount of initial inoculum. The aim of this study was to elucidate the sites and structures of survival of Colletotrichum spp. in the field. For this, in a commercial apple orchard with history of bitter rot, different organs from the plant (branches, fruit buds and mummified fruits) and from the ground (garden waste and mummified fruits) were collected at different times during two consecutive years. The samples were processed to detect the presence of vegetative and reproductive structures of this pathogen. Colletotrichum spp. was found in apple trees, mainly on the wood of the branches. It was not possible to detect the pathogen on mummified fruit nor on prunings collected from the ground. The structures found were masses of mycelium and conidia cirrus, and in no cases perithecia with asci and ascospores were found.