How to Manage Pests

Pests in Gardens and Landscapes

Exocortis— Exocortis viroid

The characteristic symptom of exocortis is the shelling of susceptible rootstocks. Exocortis is spread by a viruslike particle that kills the bark; the bark dries, cracks, and may lift in thin strips. Some droplets of gum often appear under the loose bark.


It is best to remove infected trees because pruning clippers and saws, unless thoroughly disinfected with bleach, can transmit exocortis to other trees. Some rootstocks may be less susceptible than others to exocortis.

Stunted tree
Stunted tree infected with exocortis

Bark shelling
Bark shelling on susceptible rootstock

Statewide IPM Program, Agriculture and Natural Resources, University of California
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