Special Session: Boxwood Blight: Confronting an Emerging Disease Through Collaborative Connections

106-S

The show must go on: Boxwood and beyond.
M. Ganci (1), D. M. Benson (1), J. A. LaMondia (2), K. IVORS (3)
(1) North Carolina State Univ, Raleigh, NC, U.S.A.; (2) The Connecticut Agricultural Experiment Station, Windsor, CT, U.S.A.; (3) North Carolina State University, Raleigh, NC, U.S.A.

Boxwood blight is a foliar disease caused by the fungus Calonectria pseudonaviculata. As infection progresses, foliar lesions often expand, resulting in leaf blighting and defoliation. While boxwood blight is a significant threat to established plantings of the commonly grown cultivars American (B. sempervirens) and English (B. sempervirens ‘Suffruticosa’), the vast diversity in the genus Buxus should lead to the identification of disease resistance. Outdoor trials were conducted during the growing seasons of 2012 and 2013 to evaluate the susceptibility of 51 commercial Buxus cultivars to boxwood blight in Mills River, NC. Results indicate a wide range in susceptibility to C. pseudonaviculata. In general, B. sempervirens cultivars experienced more blighting and defoliation than B. microphylla and B. sinica var. insularis cultivars. Canopy density and height also influenced susceptibility. In Connecticut trials, Korean (B. sinica var. insularis) and B. microphylla ‘Winter Gem’ were the least susceptible, American and English were the most susceptible, and Green Mountain and Green Velvet (B. sempervirens × B. sinica) were intermediate. Although the partially-resistant varieties we identified showed minimal symptom development, these plants were capable of harboring the pathogen and providing inoculum for susceptible cultivars nearby. Thus, the use of partially-resistant cultivars is just one part of an integrated management approach.