Occurrence of boxwood blight (Calonectria pseudonaviculata and C. henricotiae) in historical gardens in the Czech Republic

Buxus spp. are possibly endangered by fungal pathogens of the genus Calonectria . The first documented occurrence of the pathogen Calonectria pseudonaviculata in the Czech Republic, in 2010, was on young plants in a plant production nursery. In 2017 and 2018, Calonectria spp. were monitored on established landscape plants in 27 historical gardens. Leaf spots and dieback of the plants were recorded in 20 historical gardens. Parts of symptomatic boxwood plants were collected and pathogens present isolated. Four fungal isolates were morphologically identified as Calonectria sp. and distinguished as Calonectria pseudonaviculata and C. henricotiae by enzyme restriction within the β–tubulin PCR amplicons, sequencing, and phylogenetic analysis. The results showed that at present, both species of Calonectria pathogenic to boxwood occur in the Czech Republic.