Belarusian Oak Forests Afflicted with Armillaria Root Rot during Their Mass Desiccation

During the period of the oak forests’ mass desiccation, Armillaria root rot became widespread, exacerbating the state of depression. The infection of stands by white sapwood rot caused by fungi of the genus Armillaria was more often detected in Bug-Polesia and Berezina-Pre-Polesia forest growth areas. The incidence of the disease in the oak forests of Belarus increases with the raising of the stands age and the decrease in their density. More often, the affliction with Armillaria root rot occurs in floodplain oak forests, as well as in the dry lands forest types with the most fertile soils. The oak’s proportion in the stand’s composition does not significantly affect the occurrence of the infection. Under the conditions of massive weakening of the Belarussian oak forests, facultative parasites from the Armillaria genus can occur as dangerous secondary pathogens that accelerate the death of weakened oak trees. Their pathogenicity persists in the north of the republic, where the negative role of other pathological factors in oak forests decreases. After the end of the depression period, the transition of Armillaria from a parasitic to a predominantly saprotrophic strategy was recorded. The affliction of oak forests by Armillaria root rot can act as one of the oak formation’s condition indicators, marking the depression phase in oak stands. Therefore, the spread of foci of Armillaria root rot should be monitored while conducting forest pathology surveys and monitoring the condition of oak forests.