Clear sanitation felling as a method of control of the population density of stem pests and spreading of dendropathogenic organisms under the current conditions using Leningrad Region as a case study
The study presents the results of forest pathology monitoring and forest pest surveys, the reasons for appointments of sanitation felling, and forest pest and dendropathogen spread dynamics. A critical analysis of reasoning under sanitation felling orders and their results is given. It is concluded that the sanitation felling does not have significant affects on the density of pest populations and spreading of diseases on the territory of Leningrad Region. Strong winds are the main damaging factor in the region since 2010. According to the data of the Forest Protection Centre of Leningrad Region, the next by significance after hurricane winds reason for appointment of sanitation felling was forest diseases. Those diseases are mainly caused by Phellinus chrysoloma (Fr.) Donk, Heterobasidion annosum (Fr.) Bref., Phellinus tremulae (Bondartsev) Bondartsev & P.N. Borisov as well as spread of wound cancer and resin cancer. However, spreading of the pathogens increased after these fellings. Outbreak of European spruce bark beetle Ips typographus (L.) occurred in Leningrad Region in 2013-2015. The forest pathology inspection showed that in 2016 there was a sharp decrease of the Spruce bark beetle population density in the Sosnovsky and Zhitkowsky Forestries (north part of Karelian Isthmus) up to 500 and 1500 beetles of the parental generation per hectare, respectively. Heterobasidion annosum was absent in the surveyed area. Nevertheless, at the same location Ph. chrysoloma was registered sporadically and spruce wound cancer was wide spreading. In some areas, more than 50% of the trees had symptoms of the disease. Thus, the obtained data are in contradiction with the data of the Forest Protection Centre of Leningrad Region.