''Leptocybe invasa'', the blue gum chalcid wasp or eucalyptus gall wasp, is a
chalcid wasp
Chalcid wasps (, , for their metallic colour) are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, me ...
which is the only species in the
monotypic genus
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
''Leptocybe'' in the subfamily
Tetrastichinae
Tetrastichinae is a subfamily of the chalcid wasp family Eulophidae. It is one of the largest subfamilies of the Eulophidae containing over 100 genera and nearly 3,000 species. The species of the family Tetrastichinae are found in almost any typ ...
, of the family
Eulophidae
The Eulophidae are a large family of hymenopteran insects, with over 4,300 described species in some 300 genera. The family includes the genus ''Elasmus'', which used to be treated as a separate family, "Elasmidae", and is now treated as a subf ...
. It is a
gall wasp
Gall wasps, also incorrectly called gallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this generall ...
which causes the formation of
gall
Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...
s on a number of species of ''
Eucalyptus
''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as euca ...
'', it was
described in 2004 after galls were found in
river red gums (''Eucalyptus camaldulensis'') in the Mediterranean and Middle East and has since been found to be a widespread species where its host trees are planted. It is indigenous to Australia.
Description
This tiny wasp is just over one millimeter in length. Its body is brown with a slight blue to green
iridescence
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
. Parts of the legs are yellowish in color.
Distribution
''Leptocybe invasa'' is native to
Queensland
)
, nickname = Sunshine State
, image_map = Queensland in Australia.svg
, map_caption = Location of Queensland in Australia
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, established_ ...
, Australia where its exact distribution has yet to be determined. It has now been found as an
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
in eucalypts in northern, eastern and southern Africa, Asia, the Pacific Region, Europe as far north as the United Kingdom, southern Asia, southern South America, the Middle East, Mexico and the United States. It appears to be spreading.
[''Leptocybe invasa''.]
FAO Forest Pest Species Profiles. August 2012.[Blue Gum Chalcid.]
Pest Fact Sheet. Asia-Pacific Forest Invasive Species Network.
Discovery
''L. invasa'' was discovered in 2000 when
river red gums in the Middle East and Mediterranean began developing disfiguring
gall
Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...
s. The damage became severe enough to cause crop losses in tree plantations. Galls were collected and a previously undescribed species of chalcid wasp emerged. In 2004 it was described to science as ''Leptocybe invasa''.
[
]
Biology
The adult female injects a neat line of minute eggs in the epidermis of new leaf buds on eucalyptus trees. The leaf tissue may exude a whitish sap, which covers the oviposition site. Heavy wasp infestations can kill new buds on the trees. If the bud survives it develops a layer of corky tissue within one to two weeks of oviposition. This corky scar widens and becomes glossy in texture. It turns from green to pinkish to dark pink or red in color. It loses its glossy texture and turns dull brown or reddish. The chalcid wasp larva develops inside the gall and when it emerges as an adult insect the gall is spherical and up to 2.7 millimeters wide. During an infestation there are usually 3 to 6 galls per leaf, but up to 65 have been observed on a single leaf.[ The adult wasps emerge from the galls after growing inside for 3–4 months. In temperate areas there may be 2-3 generations of adults in a year but in the tropics there can be as many as 6 generations.] The females can reproduce asexually by thelytokous
Thelytoky (from the Greek ''thēlys'' "female" and ''tokos'' "birth") is a type of parthenogenesis in which females are produced from unfertilized eggs, as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in a ...
reproduction and live for up to 7 days, males are rare and the asexual reproduction allows ''L. invasa'' to rapidly increase its population size.
Several eucalyptus species are susceptible to the wasp. Host species include bangalay (''Eucalyptus botryoides''), apple box
''Apple Box'' is a box set by XTC compiling '' Apple Venus Volume 1'' and '' Wasp Star (Apple Venus Volume 2)'' along with their respective demo albums '' Homespun'' and '' Homegrown''. It is the third box set of their career following '' Transis ...
(''E. bridgesiana''), Tasmanian blue gum
''Eucalyptus globulus'' subsp. ''globulus'', commonly known as the Tasmanian blue gum, southern blue gum, or blue gum, is a subspecies of tree that is endemic to southeastern Australia. It has mostly smooth bark with some persistent slabs of old ...
(''E. globulus''), cider gum (''E. gunnii''), flooded gum Flooded gum may refer to the following tree species:
*''Eucalyptus grandis'', from eastern Australia
*''Eucalyptus rudis'', from Western Australia
*''Eucalyptus tereticornis
''Eucalyptus tereticornis'', commonly known as forest red gum, blue gum ...
(''E. grandis''), swamp mahogany (''E. robusta''), Sydney blue gum (''E. saligna''), forest red gum
''Eucalyptus tereticornis'', commonly known as forest red gum, blue gum or red irongum, is a species of tree that is native to eastern Australia and southern New Guinea. It has smooth bark, lance-shaped to curved adult leaves, flower buds in grou ...
(''E. tereticornis''), and manna gum
''Eucalyptus viminalis'', commonly known as the manna gum, white gum or ribbon gum, is a species of small to very tall tree that is endemic to south-eastern Australia. It has smooth bark, sometimes with rough bark near the base, lance-shaped to c ...
(''E. viminalis'').[
]
Control
Possible biological
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...
agents for ''L. invasa'' have been actively searched for and numerous hymenopteran parasitoids of ''L. invasa'' were identified; in one study in China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
these were '' Quadrastichus mendeli'', ''Aprostocetus causalis
''Aprostocetus'' is a genus of hymenopteran insects of the family Eulophidae. The genus was erected by John O. Westwood in 1833. This very large group (about 800 described species) of parasitoid wasps has a global distribution.
Species
Widesp ...
'' and ''Megastigmus viggianii
''Megastigmus'' is a genus of minute wasps. There are more than 134 described species, more than half of which undergo larval development within the seeds of trees and shrubs.
List of species
* '' Megastigmus acaciae'' Noble, 1939
* '' Megastig ...
'',[ ] and in another study in Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
these were ''Megastigmus zvimendeli
''Megastigmus'' is a genus of minute wasps. There are more than 134 described species, more than half of which undergo larval development within the seeds of trees and shrubs.
List of species
* '' Megastigmus acaciae'' Noble, 1939
* '' Megastig ...
'', ''Megastigmus lawsoni
''Megastigmus'' is a genus of minute wasps. There are more than 134 described species, more than half of which undergo larval development within the seeds of trees and shrubs.
List of species
* '' Megastigmus acaciae'' Noble, 1939
* '' Megastig ...
'', '' Selitrichodes kryceri'' and '' Quadrastichus mendeli''.[Zvi Mendel, Alex Protasov, John La Salle, Daniel Blumberg, David Brand, Manuela Branco (2017) Classical biological control of two Eucalyptus gall wasps; main outcome and conclusions. Biological Control 105: 66-78. https://doi.org/10.1016/j.biocontrol.2016.11.010]
'' Quadrastichus mendeli'' has a short developmental time[ ] and has proven to be an especially effective control agent in the Mediterranean Basin.[ '' Selitrichodes neseri'' is another eulophid ectoparasitoid which is species specific to ''L. invasa'' and was discovered in its native Australian range in 2014 and show potential as a biological control agent on ''L. invasa''.]
References
{{Taxonbar, from=Q13393715
Eulophidae
Insects described in 2004
Agricultural pest insects
Hymenoptera of Australia