Damage, symptoms and biologyThe presence of rolled leaves in late May and leaves hanging vertically during the entire season are characteristic of attacks by maple leafroller larvae.
When populations are high, the foliage turns brown and the crowns may be completely defoliated. The impact on the tree is generally negligible, but where defoliation is severe, dieback and mortality of some of the already weakened maples may occur.
The presence of leaves hanging from trees is caused by the larvae, which cut the midrib near the petiole. The rolled leaves, held together with strands of silk, form enclosures in which the larvae rest and from which they emerge only to feed. Pupation also occurs inside the leaf rolls later in the season.
During summer, the female deposits her eggs in irregular masses on the leaves or other parts of the trees. The eggs appear to hatch before fall and the larvae likely overwinter in a hibernaculum. In the spring, the young larvae feed as soon as the buds begin to swell and later roll themselves up in the leaves.
Life cycle (East of the Rockies)
Other informationThe maple leafroller is native to North America and occurs in the Great Lakes region in Canada and the United States, and in Quebec and the Maritime provinces.
Its preferred host is maple, but it occasionally feeds on other hardwoods.
On small ornamental trees, rolled leaves can simply be removed by hand early in the summer, when the larvae or pupae are still inside.
Canadian Forest Service Publications
Diet and feeding behaviour
: Feeds on the leaves of plants.
- Leafroller: Hides and feeds inside a leaf or the tip of a leaf that it has rolled up into a cigar-shaped tube.
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