''Xanthogaleruca luteola'', commonly known as the elm-leaf beetle, is a

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

species in the family

Chrysomelidae The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...

that is native to Europe but invasive in other parts of the world.http://cisr.ucr.edu/elm_leaf_beetle.html - Center for Invasive Species Research

Description

The

imago In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the imaginal stage, the stage in which the insect attains maturity. It follows the f ...

(adult beetle) is 6–8 mm in length, and ranges from yellow to green in colour, with a spot on its head, an hourglass mark and two spots on the

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

, and a broad, dark stripe along the edge of each

elytron An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

. The larvae are usually black, occasionally black and yellow, with multiple rows of dots on the back and on the sides and < 13 mm long. The

pupae A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

are orange-yellow with black

chaeta A chaeta or cheta (from Greek χαίτη “crest, mane, flowing hair"; plural: chaetae) is a chitinous bristle or seta found in annelid worms, (although the term is also frequently used to describe similar structures in other invertebrates suc ...

e. The ova are yellow, and laid in spindle-like clusters of < 25 on the undersides of the elm leaves.

Distribution

These beetles are common in the Western

Palearctic realm The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Sibe ...

from

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

to Central

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

. Indigenous to

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, they were accidentally introduced to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, and are now widespread, and are serious pests in Australia and parts of North America.

Gallery

File:NIE 1905 Elm-Insects.jpg, Drawing of beetle, larva, and eggs published in ''The New International Encyclopædia'', v. 7, 1905 File:Xanthogaleruca luteola larva - Galeruca del olmo (9550667900).jpg, Larva of ''X. luteola'' on an elm leaf File:Xanthogaleruca luteola 20060905 530.jpg, Skeletonized leaves of parasitized elm

Ecology

''X. luteola'' is a serious pest of the

elm Elms are deciduous and semi-deciduous trees comprising the flowering plant genus ''Ulmus'' in the plant family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North ...

. Both the adults and

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e feed on the emergent leaves of the elm. Repeated heavy infestation rarely kills the tree outright, but weakens it, rendering it vulnerable to disease. Falling branches encourage elm bark beetles (''

Scolytus multistriatus ''Scolytus multistriatus'', the European elm bark beetle or smaller European elm bark beetle, is a bark beetle species in the genus ''Scolytus''. In Europe, while ''S. multistriatus'' acts as vector of the Dutch elm disease, caused by the Ascomy ...

'' and '' S. schevyrewi'') to proliferate; the beetles are vectors of Dutch elm disease. Elm leaf beetles become active in the spring once temperatures rise above . In fact, weather is one of the most limiting factors in their population growth. A late spring freeze or long winter can kill off entire colonies. The imagines depart their hibernation sites (often houses), the females laying their ova on the underside of the elm leaves. The ova hatch after one week, and the larvae immediately feed on the underside of the leaves. This larval stage lasts between two and three weeks, at the end of which larvae migrate to the lower part of the trees in search of bark crevices in which to pupate. The next generation emerges in midsummer after two to three weeks' pupation, and begins feeding on the leaves. The female can lay about 800 ova, but this ovipositing may be interrupted by shortening of the

photoperiod Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...

to less than 14 hours, inducing a brief feeding bout before the search for a hibernation site. Hosts are known to include English elm ( ''U. minor'' 'Atinia'), wych (Scots) elm (''

Ulmus glabra ''Ulmus glabra'' Hudson, the wych elm or Scots elm, has the widest range of the European elm species, from Ireland eastwards to the Urals, and from the Arctic Circle south to the mountains of the Peloponnese and Sicily, where the species reaches i ...

''), American elm (''

Ulmus americana ''Ulmus americana'', generally known as the American elm or, less commonly, as the white elm or water elm, is a species of elm native to eastern North America, naturally occurring from Nova Scotia west to Alberta and Montana, and south to Flor ...

''), Siberian elm (''

Ulmus pumila ''Ulmus pumila'', the Siberian elm, is a tree native to Asia. It is also known as the Asiatic elm and dwarf elm, but sometimes miscalled the 'Chinese Elm' (''Ulmus parvifolia''). ''U. pumila'' has been widely cultivated throughout Asia, Nor ...

''), and Chinese elm (''

Ulmus parvifolia ''Ulmus parvifolia'', commonly known as the Chinese elm or lacebark elm, is a species native to eastern Asia, including China, India, Japan, Korea, and Vietnam.Fu, L., Xin, Y. & Whittemore, A. (2002)Ulmaceae in Wu, Z. & Raven, P. (eds) ''Flora of ...

''), as well as complex hybrids such as 'Homestead'. The beetle has also been reported on ''

Zelkova serrata ''Zelkova serrata'' (Japanese zelkova, Japanese elm or keyaki or keaki; ja, 欅 (ケヤキ) keyaki /槻 (ツキ) tsuki; ; ko, 느티나무 neutinamu) is a species of the genus ''Zelkova'' native plant, native to Japan, Korea, eastern China an ...

''.Sinclair et al. 1987 When ''X. luteola'' oviposits, ''U. minor'' releases plant volatiles which recruit the

egg parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasitis ...

Oomyzus gallerucae ''Oomyzus gallerucae'' is a species of chalcid wasp in the family Eulophidae. It is a parasitoid of the elm leaf beetle. The adults and larvae eat the eggs of the beetle. The species can be found in countries like France, Iran, Australia, and ...

''. ''U. minor'' is able to distinguish between

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

secretions (

small molecule Within the fields of molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs ar ...

proteinaceous compounds) and damage which occurs in the natural course of oviposition, releases different volatiles upon detection of the oviduct compounds. ''O. gallerucae'' is then able to distinguish between these different sets of volatiles and is only attracted to oviposition. Gravid ''X. luteola'' females also respond, but inversely: They are attracted to volatiles indicating undamaged and/or unoviposited ''Ulmus'' material.

Gene expression Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...

studies have shown a large number of genes to be involved in the oviposition response process. (See

Tritrophic interactions in plant defense Tritrophic interactions in plant defense against herbivory describe the ecological impacts of three trophic levels on each other: the plant, the herbivore, and its natural enemies. They may also be called multitrophic interactions when further ...

.) Jasmonic acid is released during

gravid In biology and human medicine, gravidity and parity are the number of times a woman is or has been pregnant (gravidity) and carried the pregnancies to a viable gestational age (parity). These terms are usually coupled, sometimes with additional t ...

females'

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

on ''Ulmus'' spp.

Symptoms

The first and most apparent symptoms are of skeletonization. During feeding, elm leaf beetle larvae skeletonize the leaves. They leave the outer edge and veins of the leaf intact, which gives the foliage a net-like appearance. Areas around the feeding site dry up and die, causing the leaf to drop prematurely. Adults, on the other hand, chew small, irregularly shaped holes in the expanding leaves. Trees that lose their leaves often develop a second set, only to have them consumed when the next generation is produced.

Controls

In North America, there are few natural enemies, but in Europe, the larva of the beetle are often heavily predated by the chalcidoid wasp ''

''.Meiners, T, and Hilker, M. (1997). Host location in Oomyzus gallerucae (Hymenoptera: Eulophidae), an egg parasitoid of the elm leaf beetle Xanthogalereuca luteola (Coleoptera: Chrysomelidae). ''Oecologia'', Vol. 112, No. 1 / Sept. 1997, pp 87-93. Springer Berlin / Heidelberg. ISSN 0029-8549 (print), 1432-1939 (online) 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. Soil injection presents a non-invasive alternative to trunk injections with a 2-year effect on the ''X. luteola'' population. Since overwintering elm leaf beetles infest the homes of those close to an elm leaf beetle infestation, it is suggested that all cracks outside the house should be sealed. It is discouraged to use insecticides unless there are really heavy colonies. Nearly all chemicals currently used commercially in Australia to treat Elm Leaf Beetle, regardless of brand name or delivery method, are

neonicotinoid Neonicotinoids (sometimes shortened to neonics ) are a class of neuro-active insecticides chemically similar to nicotine, developed by scientists at Shell and Bayer in the 1980s. The neonicotinoid family includes acetamiprid, clothianidin, dinote ...

insecticides. This is the chemical type that has had (2016) a two-year ban placed on it by the European Commission, owing to the association between the widespread use of these chemicals and their impact on bee populations.

References

External links

BiolibFauna EuropaeaITIS ReportNCBI
{{Taxonbar, from=Q1307509 Galerucinae Beetles of Europe Beetles of North America Beetles described in 1766 Taxa named by Otto Friedrich Müller