Ash Leaf Cone Roller had become more established in Calgary over the previous decade but hasn’t been as bad the past few years. It mainly affects Green Ash trees (Fraxinus pennsylvanica). While the insect is in the caterpillar stage the insect rolls the leaf into a cone shape, causing the objectionable look of the tree. When many leaves on a single tree are affected, the look can be unsightly and often causes major concern for the tree owner.
Key Points
- Leaves become rolled into a cone shape.
- This insect does not feed heavily on the tree
- No real damage is caused to the tree so it is mainly considered an aesthetic issue.
Tree Damage
- Young caterpillars feed on the leaf tissue. As the caterpillar gets bigger, it emerges from one leaf, migrates to a new leaf, and rolls the leaf into the characteristic cone shape.
- Overall damage is negligible. Very little actual leaf tissue is damaged by the insect. The tree is still able to photosynthesize and produce energy to feed the tree so the tree health is not heavily affected.
- It is mainly considered an aesthetic issue as populations of the insect can get quite high depending on the year and seasonal conditions.
Control Measures
Because this is mainly an aesthetic issue, we do not recommend any chemical control; the best defense is keeping your tree as healthy as possible to prevent infestation. On small trees reachable from the ground, if the infestation is minor, the rolled leaves can be pulled off to remove the unsightly rolled leaves. Since the first appearance of this insect, several natural predators (parasitic wasps) have emerged and have drastically reduced overall populations. Heavy infestation is currently fairly rare.
