Elm Leaf Beetle
Xanthogaleruca luteola, commonly known as the elm-leaf beetle, is a beetle belonging to the family Chrysomelidae.
The imago is 6–8 mm in length, ranges from yellow to green in colour, with a spot on its head, an hourglass mark and two spots on the pronotum, and a broad, dark stripe along the edge of each elytron.
These beetles are common in the Western Palaearctic ecozone from Portugal to Central Asia. Indigenous to Europe, it was accidentally introduced to North America and Australia.
Xanthogaleruca luteola is a serious pest of the elm. Both the imagines and larvae feed on the emergent leaves of the elm. Repeated heavy infestation rarely kills the tree outright, rather it usually weakens it, rendering it vulnerable to attack by insects and diseases. However, the beetle does not transmit Dutch elm disease.
The imagines depart their hibernation sites (often houses) in early spring, the females laying their ova on the underside of the elm leaves. The ova hatch after one week, the larvae immediately feeding on the undersides of the leaves. This larval stage lasts for a period of between two and three weeks, at the end of which it will migrate to the lower part of the tree in search of bark crevices in which to pupate. The next generation emerges in mid-summer after two to three weeks’ pupation, and begins feeding on the leaves. The female can lay more than 800 ova, but this ovipositing may be interrupted by shortening of the photoperiod to more than 14 hours, inducing a brief feeding bout before the search for a hibernation site.