Distribution of the invasive pathogen Diplodia sapinea on pinus spp. in Bulgaria.
One of most important invasive pathogen Diplodia sapinea was established as a pine shoot disease agent on Pinus spp. in Bulgaria. In the period 2016-2018, it was investigated that D. sapinea is a widely distributed conifer pathogen in the country. One of the reasons of this aggressive spread was the consequence of the climate change and physiological stressors like drought, nutrient deficiency and hail damage that are the main factors for successful infection by D. sapinea. In 2017-2018, the occurrence of the pathogen was investigated on 680 Pinus nigra and 120 P. sylvestris trees in 20 permanent sampling plots established in South Bulgaria. Assessment of crown condition - defoliation and discoloration on sample trees was done. The fungus was detected on all visually infected needles, cones, shoots, seeds, buds and stems. The main insect species that were established as vectors of the pathogen were the bark beetles, which help the fungus to spread over long distances. In addition to shoot and needle disease, the pathogen caused stem canker, collar rot and sap stain, cones and seeds.