Rooting Response of Boxwood Cultivars to Hot Water Treatment and Thermal Sensitivity ofCalonectria henricotiaeandC. pseudonaviculatain Diseased Boxwood (Buxusspp.)1

Abstract Boxwood blight is caused by Calonectria henricotiae (Che) and C. pseudonaviculata (Cps). Unrecognized symptoms on Buxus cuttings used for propagation could potentially serve as a source of inoculum result in pathogen spread. In this study, boxwood (Buxus spp.) cultivars ‘Justin Brouwers', ‘Nana', ‘Green Beauty', Velvet' were assessed root production after exposure to 45 C (113 F) or 47.5 (118 water 0 60 minutes 5 minute increments. The number roots greater than 1 cm (0.4 in) length produced all three months treatment up was not statistically different from the non-immersed control. A similar response observed treated minutes, except cv. ‘Nana,' which fewer control 35 heated water. Experiments conducted diseased, detached leaves susceptible cultivar Brouwers' at C, 50 (122 52.5 (127 showed significantly reduced conidia viability Che Cps 25 30 (44%) 12 (22%). After 8 water, little no sporulation either pathogen. Index words: blight, pseudonaviculata, henricotiae, Buxus, hot treatment, rooting, cuttings, plant propagation. Species study: [Calonectria Gehesquière, Heungens J.A. Crouch (Crous J.Z. Groenewald & C.F. Hill) L. Lombard, M.J. Wingf Crous] [Buxus sempervirens Brouwers'; sinica (Rehder E. H. Wilson) M. Cheng var. insularis (Nakai) ‘Nana'; B. ‘Suffruticosa'×B. ‘Suffruticosa' × Velvet'].