AbstractManyPhytophthoraspecies are pathogens on fruit trees and may cause destructive diseases. In the current study, we examined sixPhytophthoraisolates recovered from rivers in Bulgaria, representatives of the following three species:Phytophthora chlamydospora,P. pseudocryptogeaandP. syringae. Morphological traits, cardinal temperatures and growth rates of the isolates were described. We found considerable variation in the size of sporangia and significant difference in the mycelial growth rates of the twoP. pseudocryptogeaisolates, along with multiple polymorphic sites in the ITS region of one of them. In the cases of the other twoPhytophthoraspecies, no such differences were found between the isolates. BothP. chlamydosporaisolates had a lower optimum growth temperature compared with the reported in the literature for this species. In pathogenicity tests against leaves and fruits of apple, pear, cherry, apricot and plum, the isolates proved to be capable of causing infections with varying severity.P. chlamydosporashowed to be the most aggressive towards the leaves, whileP. pseudocryptogeaisolates induced the highest percentage of decay on the fruits of all tested tree species, which may suggest partial organ or tissue specificity. The demonstrated infection capacity of the described isolates points out the investigatedPhytophthoraspecies as a potential threat for the orchards in Bulgaria, if favourable conditions are available.