New pathogens causing grapevine esca and decline
Esca disease of grapevine is characterized by foliage deterioration and sudden decline of the vine. It has long been recognized as a disease, but its etiology has never been fully elucidated. The most probable cause has long been considered to be trunk infection by fungi such as Stereum hirsutum and Phellinus igniarius (APS Compendium of Grape Diseases). The true causes of the disease have now been discovered to be quite different fungi (RS 2000/125). Infection of rooted cuttings, rootstocks and grafted plants by Phaeoacremonium chlamydosporum (now renamed Phaeomoniella chlamydospora Crous ; Gams), Phaeoacremonium aleophilum and related species causes brown wood streaking, which mlay lead to a decline of young grapevines now known as "Petri grapevine decline". If these fungi infect actively growing vines (up to 8-10 years old), they cause brown wood streaking and vascular gummosis deep inside the trunk and branches, with or without foliar symptoms. This is known as "young esca", and can develop into "esca proper" if the plants are simultaneously affected by Fomitiporia punctata causing white rot. F. punctata alone does not cause esca. It should be noted that F. punctata was previously known as Phellinus punctatus, and that this fungus was frequently misidentified as P. igniarius. Further research is needed to show whether the fungi interact with each other to cause a disease complex, or whether there are simply two distinct diseases which have been confused.
The Phaeoacremonium spp. have been isolated from diseased grapevines in several European countries, Argentina, Australia, South Africa and USA (at least). It seems that they occur wherever grapevine is grown. F. punctata is also widespread. So these fungi do not present a risk of introduction into new countries. Their discovery simply resolves a old pathological problem.
Graniti et al. (2000) Phytopathologia Mediterranea 39, 16-20.