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Comparative component analysis of Calonectria pseudonaviculata epidemiology on boxwood, pachysandra and sweet box

Ping Kong: Hampton Roads Agricultural Research and Extension Center, Virginia Tech

<div>Boxwood blight caused by <em>Calonectria pseudonaviculata</em> (<em>Cps</em>) poses an increasing threat to the ornamental nursery and landscape industries as well as public and private gardens. This disease was also recently observed on pachysandra and sweet box associated with boxwood plantings in the United States. This study compared four epidemiological components among the three hosts and pathogen isolates from each hosts. Detached leaves of boxwood, pachysandra, and sweet box were inoculated with three isolates from each host and evaluated on infection rate, lesion size and conidium and microsclerotium production. Significant differences were observed in all four components among the plants but in only one component – conidium production – among the <em>Cps</em> isolates. Specifically, a greater infection rate, larger lesions and higher conidial and microsclerotial yields were observed on boxwood compared to pachysandra and sweet box. <em>Cps</em> isolates from boxwood and sweet box produced more conidia than those from pachysandra on all the test plants. These results indicate that boxwood is a preferred host for <em>Cps</em> while pachysandra and sweet box, with lower infection rates, slower disease progression and/or less conspicuous sporulation, could be perfect carriers of this pathogen. Therefore, it is important to consider pachysandra and sweet box as potential pathogen carriers when developing management programs for boxwood blight.</div>