Summary. Esca and Petri disease, two of the most important fungal trunk diseases of grapevine, are responsible for significant losses by causing premature decline and dieback in vineyards worldwide. The Portuguese Dão wine region is no exception. Local winegrowers’ knowledge on Grapevine Trunk Diseases (GTD) in general and of esca and Petri disease in particular is incomplete. The real scope of those problems has been based largely on individual perceptions rather than on a methodical evaluation of the situation. In order to get a full picture of the diseases impact, a leaflet with color pictures was produced and issued to winegrowers, accompanied by a simple questionnaire. The results of this survey represent a first indication of the extent of grapevine trunk diseases in the Dão wine region, specifically its economic impact and relevance to the local wine industry. In conjunction with the survey, several samples of wood collected from esca and Petri disease symptomatic vines, identified during the survey throughout the entire region, were processed and a collection of isolates of Phaeomoniella chlamydospora obtained. To determine the intra-specific variability among these isolates, morphological, cultural and molecular characteristics were evaluated. A protocol to study the pathogenicity with P. chlamydospora was conducted, consisting on the inoculation of cv. Touriga Nacional’s spurs with a previously studied P. chlamydospora isolate
