Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/25/2014
Publication Date: 1/26/2015
Citation: Shishkoff, N., Daughtrey, M.L., Olsen, R.T., Aker, S.M. 2015. Evaluating boxwood (Buxus spp.) susceptibility to Calonectria pseudonaviculata by inoculating cuttings from the National Boxwood Collection at the U.S. National Arboretum. Plant Health Progress. 16:11-15.
Interpretive Summary: Boxwood blight, a disease of Buxus species, was first seen in the US in 2011. It causes concern in the nursery and landscape industry because it attacks an economically and historically important ornamental plant. Research-based management practices are urgently desired by growers, home gardeners and landscape firms. For a test of disease susceptibility, an ARS plant pathologist (Shishkoff), ARS plant breeders (Aker, Oleson) and a Cornell Extension scientist (Daughtrey) collected cuttings from 42 boxwood accessions in collection of the U.S. National Arboretum. Cuttings showed a wide range in susceptibility, with nine Buxus sempervirens cultivars showing high disease levels. Nine other cultivars and species showed significant tolerance and may be able to be recommended to growers and used in breeding programs.
Technical Abstract: Forty-two accessions of boxwood in the National Boxwood Collection of the U.S. National Arboretum were inoculated with Calonectria pseudonaviculata in order to determine preliminary susceptibilities as part of a longer term evaluation of whole plants. Terminal cuttings were inoculated with a single isolate of C. pseudonaviculata and symptoms rated 7 and 11 days after inoculation. Cuttings showed a wide range in susceptibility to dip inoculation with C. pseudonaviculata under the optimal infection conditions. There were significant differences in the percent of diseased leaves and percent of defoliation among species and cultivars. Cuttings of Buxus sempervirens cultivars were among those with the highest percentage of spotted leaves, with eight cultivars showing as much disease as the susceptible control B. sempervirens ‘Suffruticosa’. All other cultivars of B. sempervirens and remaining Buxus species showed significantly less disease.