Actual status of the beech bark necrotic disease in NorthWestern Bulgaria

Abstract

In this paper we present recent findings about the beech bark necrotic disease in selected localities situated in the mountain ranges Vitosha and Stara planina in Bulgaria. The resulting values of necrotic disease expressed by the necrotisation index (I<sub>SN</sub>) ranged from 0.72 to 1.12. In Slovakia such low values of I<sub>SN</sub> were obtained only for seven out of 52 examined localities. The I<sub>SN</sub> results are more favourable than the results obtained using the same methods for four localities situated in Northern Hungary (I<sub>SN</sub> values ranging from 1.11 to 1.18). The results of monitoring of three selected biotic vectors of beech necrotic disease were follows: the focus of occurrence of the species Bucculatrix ulmella was in submountain beech forests. Considerable affinity to lower situated sites was found in Ectoedemia liebwerdella. We also found that the boundary of the occurrence of this species is approximately at 1,000 m a.s.l. The frequency values of Cryptococcus fagi were significantly influenced by the altitude. In four out of six localities we recorded the occurrence of three species of the genus Nectria: Nectria cosmariospora, Nectria galligena and Nectria coccinea.