A general health evaluation of pine plantations, namely Austrian and Aleppo pine, two of the commonest Istrian plantation species, has revealed that the Aleppo pine is mainly in good condition on all research localities. On some of them the Austrian pine exhibits general good health, while in others significant dieback of the crown parts and of whole trees in various age classes was recorded. On the pine plantations in Prklog, Marina and Kanegra, a mortality rate of 30% was registered.Laboratory analyses of the collected samples from the chosen Aleppo and Austrian pine trees enabled a complete view of the existing mycoses in the investigated plantations. The analysis of the attacked needled twigs, shed needles, dead branches and cones showed that the moust numerous pathogenic fungi on the needles were Sphaeropsis sapinea (Fr.) Dyko et Sutton and Cyclaneusma niveum (Fr.) DiCosmo, Peredo et Minter; the ones that mostly occurred on the twigs, branches and cones was S. sapinea. Along with the aforementioned fungi, Lophodermium pinastri (Schrad. ex Hook.) Chev., Lophodermium seditiosum Minter, Staley & Millar and Truncatella hartigii (Tub.) Stay. develop on pine needles, while Cenangium ferruginosum Fr. and T. hartigii attack twigs and branches.
The Aleppo pine crown needle analysis showed that 99.2% of the needles contained no fungal carpophores. However, the analysis of the shed needles (those collected on ground) were different. There were 42.6% needles with no fungi on them. The infected needles were mainly attacked by two fungi, S. sapinea and (15.4%) and C. niveum (23.3%).
A few exceptions from the general appearance of the mycoses attack on the Aleppo crown needles were recorded. There was a case with distal twig needles in a few smaller groups of the young Aleppo pines where the analysis showed 29.0% uninfected and 65.0% needles infected only by S. sapinea. The second example were the needles from the lower branches in Marina, where L. pinastri greatly outnumbered other fungi with 91.0% of the infected needles. However, these branches were under normal process of physiological dieback with their vital functions fading away, so on significant injurious impact could be assigned to the found fungi. The third example were the needles from a few Aleppo pine trees in Vozilići where Coleosporium sp. was found but with no significant impact on the surveyed pines.
A twig analysis of the Aleppo pine from several localities showed that S. sapinea was commonest fungus. Nevertheless, such records of infected twigs are rare.
On the Premantura and Luterija localities the carpophores of Phellinus pini (Th. and Fr.) Pil. were recorded on a few tree trunks. The attacked trees still showed green, though thinned crowns.
The analysis of the Austrian pine needles established 50.7% of uninfected needles. On the infected needles the most numerous fungi were S. sapinea and C. niveum (34.6% and 15.0% resp.). The crown needle analysis of the two most endangered Austrian pine plantations in Prklog and Marina revealed that there were 33.6% of uninfected needles. The attacked needles were infected by S. sapinea and C. niveum (57.3% and 15.3% resp.). The needles collected on the ground were attacked as follows: 26.5% uninfected; 5.8% by S. sapinea and 60.0% by C. niveum.
On Austrian pine twigs and branches S. sapinea largely outnumbered other fungi. On some dead twigs and branches it was accompained by C. ferruginosum. Strong presence of S. sapinea on the infected cones was also recorded.
With the intensive appearance of S. sapinea on the research areas, especially in the Prklog, Marina and Kanegra plantations, additional detailed research was done on the infected needles, twigs, branches and cones. On the Austrian pine crown needles 1-75 S. sapinea carpophores were recorded (x = 17.0) (Fig. 16), 7-179 carpophores (x = 78.4) on 1 cm twig length, and 112-279 (x = 188.7) carpophores of S. sapinea on cone scales (Fig. 17). Analyses of the ripness degree of S. sapinea carpophores collected in April, May, June, July and October in the Prklog and Marina plantations showed that they were ripe in all these months. Accordingly, fungi infection is possible throughout the year.
According to the available references and the results of this research, the S. sapinea mycosis is taken as a crucial agent of the Austrian pine dieback in the Prklog, Marina and Kanegra plantations, with slightly smaller influence on the Puntera locality. The obtained climatological data and soil productivity survey for the given research area, along with the literature references, propound that the arid period of 1991 together with poor site conditions influenced the predisposition of the Austrian pine to the S. sapinea attack on the aforementioned localities.