Ash leaf cone roller
The ash leaf cone roller is a moth that is a relatively new pest in Calgary. It affects ornamental ash trees, principally Green and Manchurian Ash.
About the ash leaf cone roller
Young caterpillars feed within the leaf tissue. As the caterpillar grows, it emerges from the leaf, migrates to a new leaf, and rolls the leaf into a characteristic cone shape. The larvae will continue to feed within this enclosure until the pupal stage. Larvae feed until mid or late June and the adult moths will emerge from the leaf cone starting about mid-July.
Although the insect can be quite prevalent on individual trees, the damage to individual trees is minor and does not interfere with overall tree health. The rolled leaves remain attached to the tree and actual leaf damage is minimal.
What we're doing
As damage to the tree is minimal, The City does not undertake any direct control measures against this pest. Since the caterpillar stage is completely enclosed, an insecticide spray program is largely ineffective.
As well, since the moth's establishment in Edmonton in 1999 at least two small parasitic wasps are noted to be associated with it and causing significant mortality. Thus, any chemical spray program would be far more detrimental to these natural enemies than to the ash leaf cone roller.