Boxwood blight can be a devastating disease on American boxwood cultivars which are extremely common in the home landscape. Complete defoliation can occur within a week and plants can die within a single growing season. Use of tolerant cultivars, cultural practices, and fungicides can reduce incidence and spread of boxwood blight.
Boxwood Blight Facts
Symptoms on leaves can appear as light or dark brown circular leaf spots with darker borders (Figure 1). These symptoms often go unobserved due to rapid defoliation. Defoliation of the lower plant canopy is often the first obvious symptom of boxwood blight (Figure 2).
Dark brown or black streak-like lesions appear on infected stems (Figure 3).
Favored by warm, humid weather.The pathogen can survive on plant debris in the soil for at least 6 years.The disease may be spread by splashing water, wind, tools, clothing, and wet hands. Long distance movement is reliant upon the transport of infected plants, infested soil, or contaminated equipment.Caused by the fungus Cylindrocladium buxicola.Management Options
If boxwood blight is suspected, contact the Pulaski County Extension office. We'll submit the sample to the UK Plant Disease Diagnostic Lab for confirmation.
The following management options are recommended:
Inspect plants prior to purchase, and do not install any plants with an unhealthy appearance.Plant boxwoods with disease tolerance, such as Buxus microphylla japonica 'Green Beauty' or Buxus sinica insularis 'Nana'.Increase plant spacing to allow for air movement.Minimize overhead watering.Homeowners can use fungicides containing chlorothalonil or tebuconazole to protect plants from infection or suppress disease development. Always follow label directions.
If plants become infected, remove them from the landscape immediately. If boxwoods grown for commercial sale are infected, they should be destroyed or not sold.
For more information on boxwood blight, contact the Pulaski County Extension Service at 606-679-6361 and request UK publication PPFS-OR-W-20 'Boxwood Blight'
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The Master Gardener Program will be offered this fall beginning in September. Applications and fee are due by August 30, 2019. Applications can be found on the Pulaski County Extension website under 'Horticulture'.
The Lake Cumberland Master Gardeners are still selling pine straw. Prices are $7 per bale. If you purchase 50 or above, bales are $6 each.
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