Beech leaf-mining weevil
The beech leaf-mining weevil (Orchestes fagi), also known as the beech flea weevil, was first detected in Canada in 2012 in Halifax, Nova Scotia. There it was causing severe defoliation on American beech trees (Fagus grandifolia). Subsequent surveys detected the presence of the insect near Sydney, Nova Scotia as well. The weevil is native to Europe where it is common.
In the spring, female weevils lay eggs in the mid-rib of beech leaves (usually one per leaf), usually in the centre of the leaf. The hatched larvae, which are white with a black head and up to 5 mm long (see photo in sidebar), feed within the leaf. They excavate a linear mine from the mid-rib toward tip of the leaf for 4-5 mm before veering off to the side of the leaf where they make a blotch shaped mine (photo). The larva pupates within the mine, and adults (2.2-2.8 mm long) emerge from the pupae in June and feed on beech leaves before finding an overwintering site in July. After the winter, adults feed on newly emerging beech leaves.
Trees at risk
Both American beech (Fagus grandifolia) and European beech (Fagus sylvatica) grow in Canada and could be affected by the weevil.
Currently, this insect is only known to be established in Nova Scotia, where several counties are infested.
The mining activity of the weevil larvae leaves a characteristic mine pattern useful for identifying the presence of the weevil. A narrow linear mine is seen from the mid-rib of the leaf to the leaf margin where there is a blotch mine (photo). The leaves may turn brown around the edges and wilt.
What you can do
If you think you have found beech leaf-mining weevil, contact the CFIA Plant Health Surveillance Unit.