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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 #383745
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: Social distancing reduces boxwood blight incidence and severity

Author
item OHKURA, MANA - Oregon State University
item NACKLEY, LLOYD - Oregon State University
item Mitchell, Jesse
item Scagel, Carolyn
item Weiland, Gerald - Jerry

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 8/4/2021
Publication Date: 10/1/2021
Citation: Ohkura, M., Nackley, L.L., Mitchell, J.N., Scagel, C.F., Weiland, J.E. 2021. Social distancing reduces boxwood blight incidence and severity. Phytopathology. 111:S2.18.

Interpretive Summary:

Technical Abstract: Boxwood blight has caused substantial losses to the nursery industry since it was first reported in the United States in 2011. The fungal pathogen, Calonectria pseudonaviculata, produces conidia that are splash dispersed. Therefore, growing boxwood plants in nurseries with tight spacing may accelerate disease spread when coupled with frequent overhead irrigation. To test this, we assessed the development and spread of boxwood blight from inoculated plants to healthy plants of the susceptible boxwood cultivar 'Green Velvet' grown in 3.8 L pots. Plants were spaced 0 or 15 cm apart and overhead irrigated once, twice, or three times a day. Healthy plants for each treatment were arranged in a 7 × 7 grid with an inoculated plant placed in the center of the grid. Center plants were inoculated in mid-July and symptoms developed 1 week later. At the 15 cm spacing, initial symptoms on inoculated plants were mild regardless of irrigation frequency (= 5% of canopy) and the disease was never observed to increase in severity or spread to healthy plants for the duration of the study (8 months). However at the 0 cm spacing, initial symptoms were more severe (= 35% of canopy) and the disease spread to adjacent healthy plants over the following 8 months, with generally greater disease severity and faster spread observed at higher irrigation frequencies. Thus, increasing plant spacing and reducing irrigation frequency could potentially mitigate further spread of boxwood blight if the disease is present in a nursery.