Botryosphaeria Dieback & Canker
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.
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