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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #392945
Research Project: Development of Knowledge-based Approaches for Disease Management in Small Fruit and Nursery Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Nursery production decisions on plant spacing and irrigation affect risks for boxwood blight

Author
item Weiland, Gerald - Jerry
item OHKURA, MANA - Oregon State University
item Scagel, Carolyn

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2022
Publication Date: 11/1/2022
Citation: Weiland, J.E., Ohkura, M., Scagel, C.F. 2022. Nursery production decisions on plant spacing and irrigation affect risks for boxwood blight. Phytopathology. 112:S3.204.

Interpretive Summary:

Technical Abstract: Oregon is the top producer of boxwood in the United States. Production of this shrub is threatened by the introduced pathogen, Calonectria pseudonaviculata, which causes boxwood blight. Boxwood blight was first detected in two Oregon nurseries in 2011 and was later detected in ten others. Therefore, a survey is being conducted to evaluate production risks for this disease. To date, 19 facilities have been surveyed, 14 of which have boxwood blight. Boxwood blight was found more frequently and was more severe in propagation systems (7% incidence, 18% canopy affected), than in container systems (4% incidence, 7% canopy affected), and was the most infrequent and mild in field systems (2% incidence, 2% canopy affected). In propagation systems, plants were always placed close together (0 cm) and irrigated frequently, which often led to disease outbreaks. Plants were irrigated less frequently in container systems, and disease incidence and severity decreased as the plants became larger and were spaced further apart (ave. 18 cm). In field systems, plants were spaced further apart (ave. 60 cm) and irrigated less frequently than container systems. Disease severity was initially low, but as the plants grew larger and the canopies merged together, disease severity increased. Based on this, most boxwood plants seem to become infected during propagation. The disease becomes less severe and harder to find as the plants are moved into container and field systems, which presents a significant challenge for those inspecting container-grown or field-grown plants for boxwood blight.