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 <i>Calonectria pseudonaviculata</i>. 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 (<i>B. sempervirens</i>) and English (<i>B. sempervirens </i>‘Suffruticosa’), the vast diversity in the genus <i>Buxus </i>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 <i>Buxus</i> cultivars to boxwood blight in Mills River, NC. Results indicate a wide range in susceptibility to <i>C. pseudonaviculata</i>. In general, <i>B. sempervirens </i>cultivars experienced more blighting and defoliation than <i>B. microphylla</i> and <i>B. sinica</i> var. <i>insularis</i> cultivars. Canopy density and height also influenced susceptibility. In Connecticut trials, Korean (<i>B. sinica</i> var. <i>insularis</i>) and <i>B. microphylla</i> ‘Winter Gem’ were the least susceptible, American and English were the most susceptible, and Green Mountain and Green Velvet (<i>B. sempervirens</i> × <i>B. sinica</i>) 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.
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