A total of 103 tree and shrub samples infected with powdery mildew were collected during 2002–2019 from locations within parks, botanical gardens and urban green areas within the Czech Republic and the powdery mildews were morphologically analyzed and identified. The most frequently represented genera were: Erysiphe (27, including former genera Microsphaera and Uncinula), Podosphaera (11, including former genus Sphaerotheca), Phyllactinia (3), Sawadaea (2) and Arthrocladiella (1). New records for the Czech Republic were: E. (U.) arcuata, E. (M.) deutziae, E. (M.) euonymicola, E. (U.) flexuosa, E. (M.) platani, E. (M.) symphoricarpi, E. (M.) vanbruntiana var. sambuci-racemosae, E. (U.) ulmi, Po. amelanchieris, Po. (Sph.) pruinosa and Po. (Sph.) spiraeae. The results were compared with the spectrum of powdery mildew species in the surrounding countries (Slovakia; Hungary; Poland and Germany (Bavaria)).

The efficacy of essential oils (EOs) from Carum carvi, Cinnamomum cassia, Cinnamomum zeylanicum, Cuminum cyminum, Eugenia caryophyllus, Foeniculum vulgare, Melaleuca alternifolia, Mentha × piperita, Origanum vulgare, Rosmarinus officinalis and Thymus vulgaris was tested against Pectobacterium carotovorum subsp. carotovorum (Pcc) and Pectobacterium atrosepticum (Pa), which cause soft rot of potato tubers. Under in vitro conditions, the highest efficacy was found for cinnamons EOs against both bacteria. The higher sensitivity of both bacteria was manifested in clove (Pcc and Pa), mint (Pcc), oregano (Pa) and thyme (Pa) EOs. Rosemary EO was the least effective. The results from the in vivo test were not consistent with those of the in vitro tests. The most significant antibacterial effect was achieved with mint EO. The bacterial strains Pcc and Pa were more sensitive to treatment with essential oils of caraway (Pcc and Pa), cinnamon (Pcc), oregano (Pa) and thyme (Pcc and Pa). In particular, based on results of in vivo test, mint EO and possibly caraway, oregano and thyme EOs can be recommend for pickling potato tubers against pectinolytic bacteria of the genus Pectobacterium.