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Viburnum Dieback

Keep your Viburnums healthy and happy!

By: Sandy Feather 2011
Penn State Extension


Q. I lost a Doublefile Viburnum in my yard a few years ago that seemed to die branch by branch. Now one on the opposite side of the yard is doing the same thing. One of the main branches has no leaves and the bark is peeling off.  Is there anything we can do to keep this from spreading to the rest of the shrub?

A. One of the most common diseases consistent with the symptoms you are describing is called botryosphaeria canker. Botryosphaeria is a common pathogen on a wide range of woody plants, including fruit trees, shade trees such as maples and sycamores; small ornamental trees, including redbuds and dogwoods; ornamental shrubs, such as rhododendrons and viburnums; and fruit-bearing shrubs including blueberries and currants.
 


'Fungus amongus'

Fungi such as botryosphaeria are always present on plants and do not cause a problem as long as the plant is not stressed in any way. It is an opportunistic fungus that takes advantage of woody plants that have been stressed by environmental factors, especially drought, poor pruning practices, winter injury and/or repeated defoliation by insects or leaf spotting diseases.
  

white viburnum blossom
Doublefile Viburnum blossoms rival Dogwood trees

Once stress occurs, the fungus invades and causes cankers. It can enter through wounds or through natural openings in the plant.  Cankers appear as sunken areas in the bark that usually expand lengthwise down the stem. The bark in a cankered area may appear roughened; it often cracks and splits, then pulls away from the stem - just as you saw on your viburnum and are seeing on your neighbor's. When the bark is cankered around a stem's circumference, the vascular system that transports water and nutrients is broken and the stem dies.

 

Although woody plants can recover from drought stress, it does leave its mark. For example, growth rings in woody plants are smaller in dry years than in years with plentiful moisture. The hot, dry weather we had this summer could have been the last straw for your second viburnum, especially if you were not able to provide irrigation during that period.

Doublefile Viburnum in bloom
Doublefile Viburnum

Winter injury can be expressed in a number of ways, including bark splitting.

Protecting viburnums from stress

WATER - Provide an inch of water weekly when we get into hot, dry weather.

MULCH - Two to three inches of mulch around the base of trees and shrubs to help conserve soil moisture, moderate soil temperatures and keep lawnmowers and weed whackers away from the trunks and stems.

PRUNING - Be sure to make proper pruning cuts that protect bark branch collars and avoid leaving stubs that create an excellent opening for this fungus to gain entrance into the plant.

TIMING - Allow plants to harden-off for winter properly; do not prune or fertilize woody plants after mid-July to minimize winter injury.

MONITOR - Protect plants from insect or disease infestations that result in defoliation.

There is no chemical control for botryosphaeria canker. Protecting plants from stress, and making sure that the site meets an individual plant's cultural requirements reduces the likelihood of plants being infested with botryosphaeria canker. Prune out and destroy any infected branches or stems.
  

MORE

Shrub photos

Viburnum Leaf Beetle

Watch for Ticks!

 

 

 


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