During a survey in three declining and three healthy poplar plantations in Serbia, six different Phytophthora species were obtained. Phytophthora plurivora was the most common, followed by P. pini, P. polonica, P. lacustris, P. cactorum, and P. gonapodyides. Pathogenicity of all isolated species to four-month and one-year-old cuttings of Populus hybrid clones I-214 and Pánnonia, respectively, was tested using both a soil infestation and stem inoculation test. Isolates of P. polonica, P. × cambivora, P. cryptogea, and P. × serendipita from other host plants were included as a comparison. In the soil infestation test, the most aggressive species to clone I-214 were P. plurivora, P. × serendipita, and P. pini. On clone Pánnonia, P. gonapodyides and P. pini were the most aggressive, both causing 100% mortality, followed by P. cactorum, P. × cambivora, and P. polonica. In the underbark inoculation test, the susceptibility of both poplar clones to the different Phytophthora species was largely similar, as in the soil infestation test, with the exception of P. polonica, which proved to be only weakly pathogenic to poplar bark. The most aggressive species to clone I-214 was P. pini, while on clone Pánnonia, the longest lesions and highest disease incidence were caused by P. gonapodyides. Phytophthora cactorum and P. plurivora were pathogenic to both clones, whereas P. × cambivora showed only weak pathogenicity. The implications of these findings and possible pathways of dispersion of the pathogens are discussed.

The role of Ophiostoma quercus in oak decline, a significant threat to European oak ecosystems, has been debated for nearly a century. This long-term field experiment assessed the aggressiveness of O. quercus on Quercus petraea and monitored both fungal spread and tree defense responses, combining pathology, microscopy, X-ray tomography, FTIR, HPLC and proteome analyses. Fifty-nine months post-inoculation, 30 % of trees exhibited decline symptoms, while 70 % displayed extensive cankers and lesions, 28.3 times larger than those on controls. Infected trees responded by forming tyloses, blocking water transport around the inoculation site. Following infection, increased deposition of polyphenolic compounds was observed in both barrier and reaction zones. Histopathological observations and FTIR measurements revealed enhanced local deposition of suberin, lignin, lignin-related compounds, and tannins within the lumens of ray parenchyma cells, and the cell walls of both libriform fibers and vessels. Proteomic analyses suggest that host trees are employing a salicylic acid-based defense strategy. At the tissue level, these analyses indicate a shift in metabolic pathways, with downregulation of lignin biosynthesis and upregulation of flavonoid and stilbenoid biosynthesis, as evidenced by increased chalcone synthase abundance. Our groundbreaking use of submicron-computed X-ray tomography on woody tissues could pave the way for the widespread adoption of non-destructive 3D scanning technology in plant-fungal interaction research. The findings of this study demonstrated the aggressiveness of O. quercus towards adult Q. petraea and its contribution to the widespread syndrome of oak decline.

Within the Daedaleopsis genus six species has been described, however, some sources are indicating that there are 10(11) species. Two species are occurring in Europe, including D. confragosa (with its variety tricolor) and D. septentrionalis. Daedaleopsis confragosa causes white rot of broadleaved hosts and most often appears as saprotroph, less often at living trees as opportunistic parasite. Basidiomes of D. confragosa form two types of hymenophore and express differences in the color of upper surface. Based on this, two species were separated in the past including D. confragosa with pores and D. tricolor with lamelloid hymenophore. The aims of this study were to isolate the fungus from morphologically different fruiting bodies and to determine whether there is any difference in growth rates and morphology of pure cultures. It was recorded that reaction and growth on media amended with gallic or tannic acid are identical, and there were no substantial differences in growth rates at different temperatures. Both types of fruiting bodies at short distances were recorded on the same branches in some cases, and after the isolation tests morphologically identical cultures were obtained. Based upon these results and previously performed molecular studies, we believe that there is no reason for D. tricolor to be considered even as a variety, and that is a single species D. confragosa. Fungus D. confragosa has medicinal properties showing cytotoxic, analgesic, anticancer, antifungal, antibacterial and antiviral effects.

The epidemic dieback of conifer forest, as the modern phenomenon, is present in the central part of the Republic of Serbia as well as in other countries of Southeastern Europe. Affected forest area increased in the period 2011-2014. It was most intense in forest stands dominated by spruce and silver fir, and about eight-fold less intense in Austrian and Scots pine. Change in climate conditions is supposed to be one of the main possible causes of coniferous forests dieback. The climate change initiated the increased activity of fungi Armillaria spp. and Heterobasidion annosum which led to the decay of individual trees and spreading in groups of trees. In pine and spruce monocultures afforested within the broadleaved habitats, massive dieback of trees was also a consequence of these two fungi. Spatial and temporal scales of insect outbreaks increase due to dry summers and mild winters in high elevations. In the last decade, in the coniferous plantation and natural forests in the central part of Serbia, intense outbreaks of bark beetles on spruce and silver fir were recorded. Spruce forests were heavily attacked by Ips typographus and Pityogenes chalcographus, and Austrian and Scots pine forests have been mostly affected by forest fires followed by outbreaks of Ips sexdentatus and other bark beetles. Insufficient silvicultural measures and inappropriate forest management in silver fir forests contribute to mistletoe infestations.

During the last several years, a significant decline of different forests in Serbia was recorded. The decline is more widespread in conifer stands, but occurence of decline was recorded in broadleaved forest stands as well. These declines are the result of abiotic, biotic and anthropogenic factors. According to the studies performed so far in Serbia, the predisposing factor were droughts during the 2012 and 2013 vegetation periods that caused physiological weakness of the trees. Among the biotic factors, the most important are fungi (mainly root rot, but rot fungi, and needle diseases) and insects (bark beetles in conifer species) and defoliators in broadleaved species).