| Xanthogaleruca luteola | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Superfamily: | Chrysomeloidea |
| Family: | Chrysomelidae |
| Subfamily: | Galerucinea |
| Genus: | Xanthogaleruca |
| Species: | X. luteola |
| Binomial name | |
| Xanthogaleruca luteola (Müller, 1766) |
|
| Synonyms | |
|
|
Xanthogaleruca luteola, commonly known as the Elm Leaf Beetle, is a serious pest of the elm. Indigenous to Europe, it was accidentally introduced to North America[1]. 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 other insects and diseases. However, the beetle does not transmit Dutch elm disease.
Contents |
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. The larvae are usually black, occasionally black and yellow, and < 13 mm long. The pupae are orange-yellow with black chaetae. The ova are yellow, and laid in spindle-like clusters of < 25 on the undersides of the elm leaves [1].
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 < 800 ova, but this ovipositing may be interrupted by shortening of the photoperiod to < 14 hours, inducing a brief feeding bout before the search for a hibernation site.
The larval feeding pattern leaves the upper surface and veins of the leaf intact, but causes it to wither and fall. The feeding imagines create small irregular but discrete holes in the leaves, and are generally less destructive than their offspring.
In North America, there are few natural enemies, but in Europe, the ova of the beetle are often heavily predated by the chalcidoid wasp Oomyzus gallerucae [2]. Insecticide sprays are of little use since by the time the infestation is apparent, the application will be too late to be effective. However, tree trunks banded with insecticides can limit repetition the following year by killing the larvae as they descend before hibernation.