European Elm Scale has become a large problem in Calgary in the last decade. Symptoms are not obvious unless the infestation level is quite high. Prevention is tough when untreated trees are nearby as the insects move fairly easily between trees. As with most insects and disease, a healthy tree is less likely to be affected. This means that keeping your tree as healthy as possible is the best defense against infestation by this insect.
Key Points
- Bark of severely infested trees turns black and sticky sap “rains” from the tree.
- Leaves may turn yellow or drop off of the tree prematurely.
- Many Elms in Calgary have been significantly damaged by the insect.
- If you suspect your Elm may be infected it is recommended that you contact a professional Arborist to discuss the best treatment options.
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.
