Maple leafcutter

Green foliage inside the defoliated ring, seen after removing the habitaculum, and series of disks forming the habitaculum Thérèse Arcand

French common name: Coupe-feuille de l'érable
Scientific name: Paraclemensia acerifoliella (Fitch)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Incurvariidae

Distribution

Eastern Canada

Damage, symptoms and biology

In summer, oval holes of variable size and small defoliated rings on the upper surface of leaves (which have an intact green centre) are signs of maple leaf cutter attacks.

On leaf surfaces, small oval disks can also be observed; these disks have been cut by larvae that are mining into the foliage. The cases consist of two superimposed disks attached to the leaf surface. Destruction of the upper epidermis by larval feeding and the many cases cut by larvae at each moult lead to foliage desiccation.

In spring, when the leaves are unfolding, the female deposits her eggs in a tiny pocket just under the lower epidermis of the leaf. After hatching, the larvae begin to mine into and feed on the parenchymal tissues between the upper and lower epidermis. They later cut cases out of the leaf and live as case-bearers. The older larvae feed on the leaf's surface, eating the foliar tissues in a circle around the case as far as they can reach. When full grown, the larvae fall to the ground within their cases; they subsequently spin a silk cocoon and change into a chrysalid. The insect overwinters in this stage.

Other information

There have been numerous maple leaf cutter outbreaks in Eastern Canada over the past two centuries. This species is native to North America. The two largest and best known infestations were reported in Ontario and Quebec during the period 1939 to 1965. Since then, there have been periodic outbreaks, with the level of damage varying from year to year.

To protect ornamental trees from a maple leaf cutter infestation two years in a row, it is important to collect and burn all the dead leaves in the fall. This will destroy the overwintering populations of chrysalids.