Sphaeropsis sapinea: The Cultural Characteristics of Isolates in Relation to Various Impacts on Pines in Croatia

Since 1992 outbreaks of Sphaeropsis sapinea have been reported in pine plantations in several localities. Differences in the presence of the fungus and its injurious impact on pine trees in Croatia have been recorded. In some localities, S. sapinea was found on needles in the litter, or on fallen branches and cones, while in other localities the dieback of shoots, branches and crown were associated with the presence of the fungus. In order to reveal the possible reason(s) for these differences in the occurrence of S. sapinea, 17 isolates were collected from all over the country and compared in several aspects. Isolates from the Netherlands were used as references. The study revealed no differences in the morphological characteristics of the cultures or in sporulation. Significant differences in the growth rate of the isolates were found, but these could not be correlated with the symptoms observed in the field. The hypothesis that the presence of different strains of S. sapinea causes outbreaks of fungus on pines in Croatia was rejected. Other possible reasons for fungus outbreaks in several localities are discussed