European Elm Scale

European Elm Scale has become a bigger problem in Calgary in the last 6 or 7 years. Symptoms are not obvious unless the infestation level is high. Prevention is tough when untreated trees are nearby as the insects move fairly easily. As with most insects and disease, a healthy tree is less likely to be affected.

Tree Damage

  • This insect feeds by piercing leaves and bark and sucking juices from the tree.
  • The nymph and adult stages feed heavily on the tree.
  • Leaf yellowing and early dropping of leaves.
  • Honeydew material falls from the tree canopy and coats most things underneath causing bark to turn a black color.
  • Dieback of branches and inner crown.

  • Control Measures

    If you suspect your Elm has scale we recommend contacting a professional Arborist to discuss treatment options. Usually a combination of dormant season pruning and chemical controls applied by qualified professional is the best option. Elms in Calgary should only be pruned between October 1st and March 31st by law to prevent the spread of Dutch Elm Disease.