Apple lenticel rots: state of knowledge on the epidemiology of Neofabraea vagabunda

Lenticel rots are one of the primary postharvest diseases affecting apples in long-term storage, and include Bull's-eye Rot (BER) and Colletotrichum, that cause economic losses and are controlled by preharvest treatments. Neofabraea vagabunda is the major causal agent of BER in France, Italy, and in many other countries of Western Europe. Infection occurs on fruits through lenticels prior to harvest where the fungus remains dormant (latent infection) until symptoms develop after several months of cold storage. Information on the epidemiology of N. vagabunda, however, is lacking. The source of inoculum has been recently assessed and found in both the orchard and the general environment. In contrast to N. perennans, N. vagabunda usually does not induce canker formation in bark tissues. Utilizing artificial inoculation, however, we have found that the fungus can survive and produce conidia in cracks of the bark. The incidence and the effect of environmental conditions on the infection level in orchards has been investigated in the past several years by picking fruits on different dates. The role of rain has been demonstrated and the minimal wetness required for fruit infection has been shown to be related to temperature. It is possible to determine the potential of infection by N. vagabunda for each rain event and analyze the most correlated parameters with the level of infection. This could serve as a starting point for modeling this disease.