Botryosphaeria Dieback & Canker of Viburnum

Disease Information

Botryosphaeria Dieback & Canker

Symptoms and damage

The fungal disease called Botryosphaeria dieback and canker, caused by Botryosphaeria spp., is most likely to occur on plants suffering from drought stress, bark injuries, pruning wounds or other environmental stresses. Healthy plants are much more resistant to infection byBotryosphaeria spp., as they will wall off the fungus and prevent its spread through the branch.

Upon entry via a wound, the fungus kills cambium and sapwood tissue, causing sunken dead areas called cankers. The cankers are small initially, but enlarge or coalesce (merge) into large areas that girdle the branch or trunk. Water movement is stopped beyond that point and results in a rapid wilting or browning of foliage. Branches with cankers may fail to leaf out in the spring.

Management

 Water shrubs weekly during the growing season if insufficient rainfall occurs. Mulching shrubs helps to avoid mechanical injury to trunk and limbs by weed trimmers and lawn mowers. Mulch shrubs with a 2- to 4-inch layer of bark, pine needles or ground leaves, and avoid piling the mulch against the trunk.

Prune any branches with cankers back to green healthy wood. If entire branches must be pruned, cut the limb just outside the branch collar and not flush with the trunk. Disinfest pruners between every cut with a 70% alcohol or 10% bleach solution. Dispose of all prunings, as this plant material is a potential source of disease for viburnums as well as other woody shrubs. No fungicides are recommended for the control of fungal cankers, but pruning wounds may be sprayed for protection with a benzimidazole fungicide, such as thiophanate methyl.

 



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