The pathogen that causes boxwood blight, Calonectria pseudonaviculata, is able to infect every species in the Buxaceae family. A recent article in Plant Health Progress, authored by Dr. Jim LaMondia of the Connecticut Agricultural Experiment Station (CAES), states that both Allegheny spurge, Pachysandra procumbens, and the more commonly planted Japanese spurge, Pachysandra terminalis, are potential hosts for boxwood blight. The article described the ability of boxwood blight to infect native Pachysandra species under lab conditions. This same lab had conducted similar studies of the susceptibility of Japanese spurge to the disease last year, which then yielded over 20 confirmed cases of boxwood blight on landscapes in Connecticut.
A very concerning result from this study concludes that boxwood blight is more aggressive when infecting Allegheny spurge than it is when hosting on Japanese spurge. On the native species, necrotic lesions appear on leaves and stem, eventually girdling stems leading to leaf and shoot death. Sporulation also appeared more vigorous on Allegheny spurge.
Both Japanese and Allegheny spurge are commonly planted with boxwood species in residential and formal landscapes. The potential for all of these species to host boxwood blight presents further complications for controlling the spread of the disease. Allegheny spurge is listed as threatened in portions of its native range, boxwood blight can further imperil the plants. For more information on boxwood blight, disease control and plant healthcare contact your arborist and visit: http://www.savatree.com/tree-disease-treatment.html.