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Abstract
Boxwood (Buxus spp.) are valuable landscape plants that are currently suffering from decline caused by plant pathogens such as Phytophthora species. High soil moisture is associated with boxwood decline. These experiments were designed to evaluate the effect of mulching and irrigation on Buxus sempervirens Suffruticosa and to evaluate eight Buxus cultivars for susceptibility to these pathogens. Mulching did not increase growth and may promote the development of disease when Phytophthora nicotianae Breda de Haan was present in the soil. Additional irrigation did not have significant effects on growth of Suffruticosa. Only Suffruticosa inoculated with P. nicotianae showed significant reduction in growth, and they gradually developed symptoms of Phytophthora root rot. The B. sinica cultivars and the B. sempervirens cultivars were susceptible to P. nicotianae, while the B. microphylla cultivars were less sensitive to P. nicotianae. All the cultivars were less sensitive to Phytophthora cinnamomi Rands.