Texas Invasive Species InstituteXanthogaleruca luteola
Elm Leaf Beetle
Synonyms: Chrysomela luteola, Pyrrhalta luteola
Class: Insecta
Order: Coleoptera
Family: Chrysomelidae
Photographer: Joseph Berger Photographer: Clemson University- USDA Extension
Source: Bugwood.org Source: Bugwood.org
Adult Description: Xanthogaleruca luteola is a yellow to olive green beetle from the Chrysomelidae family. It has a pronotum with central spots and two lateral spots. On the elytra there is a broad stripe along the outer edge and a sometimes vague medial stripe. However, sometimes this species can have a darker morphology when it overwinters.
Larvae Description: The larvae are very conspicuous by being yellow with black spots and stripes. They are usually found feeding on the leaves and grow up to one half-inch in length.
Host plant: Elm trees from the genus Ulmus including the American, Chinese and Siberian elm trees.
Ecological Threat: Over the years this beetle has become a major pest of elm trees. Since both the adults and larvae feed on the leaves, they can be skeletonized if the attack is severe. Most trees will not be killed unless the defoliation is severe for two or three consecutive years. Thankfully this beetle does not transmit Dutch elm disease; but it does spread quickly and is a most unwelcomed pest.
Biology: Adults overwinter in protected locations such as homes, garages, and woodpiles and under yard debris. They are not house pests when they overwinter, and they do not reproduce during that period. They emerge in the spring when it warms up and they begin to move about and leave the house. They fly to elm trees, depositing yellow, lemon-shaped eggs in groups of 25 or more on the undersides of leaves. Larvae hatch about a week after egg deposition. Three weeks later the larvae are fully mature and pupate at the base of the tree. After pupation for 14 days adults emerge, three or more generations can occur in a year. Both larvae and adults feed on the leaves.
History: This beetle was first detected in Baltimore, Maryland in the late 1830s. Present day it has invaded all of the continental United States.
U.S. Habitat: Since it has been able to establish itself in 48 of the states this insect has high tolerance for different ecosystem and environmental conditions. It can be found anywhere elm trees are present.
Distribution
Native Origin: Portugal to Central Asia
U.S. Present: All states except Alaska and Hawaii
Resembles/Alternatives
The elm leaf beetle resembles the species in the genus Trirhabda. However, they can be told apart by their 3rd antennal segment in relation to their 4th. For Trirhabda the 3rd antennal segment is shorter than the 4th while for Xanthogaleruca the 3rd segment is longer.
Management
Since the late 1970s the horticultural industry has done more research into creating insect-resistant trees; so newer elm tree strains are more resistant to several pests. However, this beetle is still able to persist.
The elm leaf beetle can be treated with insecticides containing carbaryl and azadirachtin. To minimize leaf injury to elms, apply the insecticides after the eggs have hatched and while the larvae are small. First the carbaryl-insecticide must be sprayed in a 3 foot band around the trunk of the tree. The second step is treatment with azadirachtin and it must be applied to the branches and foliage of the tree must be sprayed until they’re saturated. Re-application must occur each spring for 2 to 3 years after initial application.
References
Thurston, G. S. 1998. Biological control of elm leaf beetle. Journal of arboriculture, 24.
Internet Sources
http://www.biol.uni.wroc.pl/cassidae/European%20Chrysomelidae/xanthogaleruca%20luteola.htm
http://www.colostate.edu/Depts/CoopExt/4DMG/Pests/elmleaf.htm
http://entoweb.okstate.edu/ddd/insects/elmleafbeetle.htm
http://extension.missouri.edu/p/G7356
https://insects.tamu.edu/fieldguide/bimg186.html
