Efficacy of Fungicides for Control of Boxwood Blight in Oregon, 2025

Boxwood blight, caused by the fungal pathogen Calonectria pseudonaviculata , is the most serious disease affecting boxwood ( Buxus species and cultivars) in the United States nursery industry. Symptoms include leaf spots, leaf blight, defoliation, and small, black stem lesions. This report evaluates the efficacy of fungicide treatments for the management of boxwood blight. The trial was conducted in 2025 in Corvallis, OR, on 15-inch-tall plants of ‘Green Velvet’ boxwood in 1 gal containers. Results from these trials will help register new pesticides for this crop and assist U.S. boxwood growers and landscapers in choosing appropriate treatments for this disease.