WSU Extension

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Caption: Boxwood canker
Photo by: R.S. Byther
  
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Boxwood : Canker
(revision date: 4/11/2018)


Biology
Boxwood canker is caused by a fungus which often infects branches through pruning wounds or at branch crotches, where infected, dead leaves have accumulated. Leaves of affected branches often change color to light green, yellow, then tan. The leaves of affected twigs turn upward and lie close to the branch. Twigs may die back above the infection site. Fungal fruiting bodies may be present on the affected leaves. They are rose-colored and waxy in appearance. English or common boxwood (Buxus sempervirens) is reported to be susceptible to canker.
Management Options

Non-Chemical Management
  • Provide proper culture for plants, including proper irrigation and fertilization. Healthy plants are more disease-resistant.
  • Plant in well-drained soil.
  • Avoid wounding plants.
  • Prune and destroy affected branches.
  • Collect and destroy fallen leaves in and under infected plants, particularly those accumulated in branch crotches.
Select non-chemical management options as your first choice!

Chemical Management


Apply in spring before growth starts. Additional applications in late spring, summer, and fall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • This list may not include all products registered for this use.
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Caption: Boxwood canker
Photo by: R.S. Byther