Northern Tamarisk Beetle

''Diorhabda carinulata'' is a species of leaf beetle known as the northern tamarisk beetle, which feeds on tamarisk trees from southern Russia and Iran to Mongolia and western China.Tracy and Robbins (2009) provide a detailed review of the distribution, biogeography, biology, and taxonomy of ''D. carinulata'' that is a general source for most of this article. This beetle is used in North America as a biological pest control agent against saltcedar or tamarisk (''Tamarix'' spp.), an invasive species in arid and semiarid ecosystems (where ''D. carinulata'' and its closely related sibling species are also less accurately referred to as the 'saltcedar beetle', 'saltcedar leaf beetle', 'salt cedar leaf beetle', or 'tamarisk leaf beetle').(Tracy and Robbins 2009).

Taxonomy

The northern tamarisk beetle was first described from southern Russia as ''Galeruca carinulata'' Desbrochers (1870). Weise (1893) created the genus ''Diorhabda'' and erroneously placed the northern tamarisk beetle as a junior synonym of a sibling species, the Mediterranean tamarisk beetle, '' Diorhabda elongata'' (Brullé). Chen (1961) described the species in western China as a new subspecies ''Diorhabda elongata deserticola'' Chen. Yu ''et al.'' (1996) proposed the species ''D. deserticola''. Berti and Rapilly (1973) recognized the northern tamarisk beetle as a separate species ''Diorhabda carinulata'' (Desbrochers) based on detailed morphology of the endophallus of the male genitalia. Tracy and Robbins (2009) confirmed the findings of Berti and Rapilly (1973), established ''D. e. deserticola'' as a junior synonym to ''D. carinulata'', and provided illustrated taxonomic keys separating the northern tamarisk beetle from the four other sibling species of the ''D. elongata'' (Brullé) species group: '' Diorhabda elongata'', '' Diorhabda carinata'' (Faldermann), '' Diorhabda sublineata'' (Lucas), and '' Diorhabda meridionalis'' Berti and Rapilly. In literature prior to 2009, ''D. carinulata'' was usually referred to as ''D. elongata'', a China/Kazakhstan ecotype of ''D. elongata'' (in the US), or ''D. elongata deserticola''.

Host plants

Extensive literature on the biology and host range of the northern tamarisk beetle in Kazakhstan, China, and Mongolia is found under the names ''D. elongata'' and ''D. e. deserticola''. The northern tamarisk beetle is a well-known pest of tamarisk in western China, where in certain years large outbreaks of the beetle can defoliate thousands of acres of tamarisk trees. The species is controlled in western China to protect plantings of tamarisk for windbreaks and soil stabilization. In nature, the northern tamarisk beetle feeds on at least 14 species of tamarisk and the closely related genus ''Myricaria''. All these food plants are restricted to the tamarisk plant family Tamaricaceae. Extensive laboratory host range studies verified it is a specialist feeder only on plants of the tamarisk family. In North America, it prefers ''T. ramosissima'' to ''T. parviflora'' in the field and this preference is also seen in laboratory studies. In laboratory and field cage studies, the northern tamarisk beetle will also feed and complete development on ''Frankenia'' shrubs, distant relatives of tamarisks in the same plant order Caryophyllales which have species native to North America, but they greatly prefer to lay eggs upon tamarisk. Field studies in Nevada confirm the beetle will not significantly attack ''Frankenia'' (Dudley and Kazmer 2005).

Lifecycle

The northern tamarisk beetle overwinters as adults on the ground in leaf litter beneath tamarisk trees. Adults become active and begin feeding and mating in the early spring when tamarisk leaves are budding. Eggs are laid on leaves, and hatch in about a week in warm weather. Three larval stages feed on tamarisk leaves for about two and a half weeks, when they crawl to the ground and spend about five days as a “C”-shaped inactive prepupa before pupating about one week. Adults emerge from pupae to complete the lifecycle in about 4–5 wk in the summer. (For images of various life stages, see ''Diorhabda carinulata'' at commons.) From two to four generations of tamarisk beetles occur through spring and fall in central Asia. In the late summer and early fall, adults begin to enter diapause in which they cease reproduction and feed to build fat bodies before seeking a protected place to overwinter beneath the tamarisk. Larvae and adults are sensitive to shorter day lengths as the summer progresses that signal the coming of winter and induce diapause. Cossé ''et al.'' (2005) identified an aggregation pheromone that adult male northern tamarisk beetles can emit to attract both males and females to certain tamarisk trees.

Biological control agent

The northern tamarisk beetle is currently the most successful biological control agent for tamarisk in North America. Populations taken from around 44°N latitude at Fukang, China, and Chilik, Kazakhstan, were initially released by the USDA Agricultural Research Service in 2001. Since its release, the insect has defoliated tens of thousands of acres of tamarisk in Nevada, Utah, Colorado, and Wyoming. However, it appears to be poorly adapted to some areas where other species of Old World tamarisk beetles are being introduced, such as the Mediterranean tamarisk beetle, '' Diorhabda elongata'', in northern California and parts of West Texas, and the larger tamarisk beetle, '' Diorhabda carinata'' (Faldermann), and the subtropical tamarisk beetle, '' Diorhabda sublineata'' (Lucas), in parts of West Texas.

Tamarisk does not usually die from a single defoliation from tamarisk beetles, and it can resprout within several weeks of defoliation. Repeated defoliation of individual tamarisk trees can lead to severe dieback the next season and death of the tree within several years. Tamarisk beetle defoliation over the course of at least one to several years can severely reduce the nonstructural carbohydrate reserves in the root crowns of tamarisk. Biological control of tamarisk by the northern tamarisk beetle will not eradicate tamarisk, but it has the potential to suppress by 75–85%, after which both northern tamarisk beetle and tamarisk populations should reach equilibrium at lower levels.

A primary objective of tamarisk biological control with the northern tamarisk beetle is to reduce competition by exotic tamarisk with a variety of native riparian flora, including trees (willows, cottonwoods, and honey mesquite), shrubs (wolfberry, saltbush, and baccharis), and grasses (alkali sacaton, saltgrass, and creeping and basin wildryes). Unlike expensive chemical and mechanical controls of tamarisk that often must be repeated, biological control does not harm native flora and is self-sustaining in the environment. Recovery of native riparian grasses can be quite rapid under the once-closed canopy of repeatedly defoliated tamarisk. However, beetle defoliation can locally reduce nesting habitat for riparian woodland birds until the native woodland flora is able to return. In some areas, tamarisk may be replaced by grasslands or shrublands, resulting in losses of riparian forest habitats for birds. Releases of tamarisk beetles in southern California, Arizona, and along the Rio Grande in western New Mexico, are currently delayed until concerns can be resolved regarding safety of tamarisk biological control to nesting habitats of the federally endangered southwestern willow flycatcher (''Empidonax traillii'' ''extimus''), which will nest in tamarisk. The northern tamarisk beetle has defoliated some tamarisk nest trees of the southwestern willow flycatcher on the Virgin River in southern Utah, and actions to protect the flycatcher are under consideration. In 2010, the USDA Animal and Plant Health Inspection Service (APHIS) officially discontinued its program for release of the beetle in 13 northwestern states over concern for the flycatcher. The Colorado Department of Agriculture is continuing to redistribute beetles within their state, and they are seeing vigorous growth of native vegetation such as willows in response to reductions in tamarisk by the northern tamarisk beetle.(Johnson 2010).

References

* ; ; 2007a: Seasonal timing of diapause limits the effective range of ''Diorhabda elongata deserticola'' (Coleoptera: Chrysomelidae) as a biological control agent for tamarisk (''Tamarix'' spp.). ''Environmental Entomology'', 36(1): 15–25
PDF
* ; ; ; 2007b: Diapause in the leaf beetle ''Diorhabda elongata'' (Coleoptera: Chrysomelidae), a biological control agent for tamarisk (''Tamarix'' spp.). ''Environmental Entomology'', 36(3): 531–540
PDF
* ; 1973: Contribution a la faune de l’Iran; Voyages de MM. R. Naviaux et M. Rapilly (Col. Chrysomelidae). ''Annales de la Société Entomologique de France'', 9(4): 861–894. (In French)
* 1961: New Species of Chinese Chrysomelidae. ''Acta Entomologica Sinica'', 10(4–6): 429–435. (In Chinese with English summary)
* ; ; ; ; 2005: The aggregation pheromone of ''Diorhabda elongata'', a biological control agent of saltcedar (''Tamarix'' sp.): Identification of two behaviorally active components. ''Journal of Chemical Ecology'', 31(3): 657–670
PDF
* ; ; ; ; 2009: Host plant quality of ''Tamarix ramosissima'' and ''T. parviflora'' for three sibling species of the biocontrol insect ''Diorhabda elongata'' (Coleoptera: Chrysomelidae). ''Environmental Entomology'', 38(5): 1373–1378
PDF

* ; ; ; ; ; 2003: Host specificity of the leaf beetle, ''Diorhabda elongata deserticola'' (Coleoptera: Chrysomelidae) from Asia, a biological control agent for saltcedars (''Tamarix'': Tamaricaceae) in the western United States. ''Biological Control'', 27: 117–147
PDF
* ; 2004: Biological control programs for integrated invasive plant management. In: ''Proceedings of Weed Science Society of America Meeting, Kansas City, MO. Weed Science Society of America (CD-ROM)''. 17 pp
PDF
* ; ; ; ; 2000: Ecological interactions in the biological control of saltcedar (''Tamarix'' spp.) in the United States: toward a new understanding. In: N. R. Spencer (ed.), ''Proceedings of the X International Symposium on Biological Control of Weeds, 4–14 July 1999, Montana State University.'' Bozeman, Montana, pp. 819–873
PDF
* 1870: Descriptions de Coléoptères nouveaux d’Europe et confins. ''L’Abeille'', Volume 7, Part 1: 10–135. (In French)
* 2004: Saltcedar (''Tamarix'' spp.), endangered species, and biological weed control-can they mix? ''Weed Technology'', 18(5): 1542–1551
PDF
* ; 2005: Field assessment of the risk posed by ''Diorhabda elongata'', a biocontrol agent for control of saltcedar (''Tamarix'' spp.), to a nontarget plant, ''Frankenia salina''. ''Biological Control'', 35: 265–275
PDF
* ; ; 2006: Status of biological control of ''Tamarix'' spp. in California. In: M. S. Hoddle and M. W. Johnson (eds.), ''Proceedings of the Fifth California Conference on Biological Control, 25–26 July 2006, Riverside, CA.'' University of California at Riverside, Riverside, California, pp. 137–140
PDF
* 2010: USDA stops using beetles vs. invasive saltcedar. ''Associated Press'', 21 June 2010

* ; ; ; ; ; ; 2007: Defoliation by introduced ''Diorhabda elongata'' leaf beetles (Coleoptera: Chrysomelidae) reduces carbohydrate reserves and regrowth of ''Tamarix'' (Tamaricaceae). ''Biological Control'', 43: 213–221
PDF
* 2010: In battle of bug vs. shrub, score one for the bird. ''New York Times'', 22 June 2010

* ; ; ; ; 2003a: Assessment of risk to native ''Frankenia'' shrubs from an Asian leaf beetle, ''Diorhabda elongata deserticola'' (Coleoptera: Chrysomelidae), introduced for biological control of saltcedars (''Tamarix'' spp.) in the western United States. ''Biological Control'', 27: 148–166
PDF
* ; ; ; ; 2003b: Biology of ''Diorhabda elongata deserticola'' (Coleoptera: Chrysomelidae), an Asian leaf beetle for biological control of saltcedars (''Tamarix'' spp.) in the United States. ''Biological Control'', 27: 101–116
PDF
* ; 2006: Host specificity of different populations of the leaf beetle ''Diorhabda elongata'' (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (''Tamarix'' spp.). ''Biological Control'', 36: 32–48
PDF
* ; 1999: Biological control of saltcedar in the United States: Progress and projected ecological effects. In: Bell, C.E. (Ed.), ''Arundo and Saltcedar: The Deadly Duo, Proceedings of the Arundo and Saltcedar Workshop, 17 June 1998. Ontario, California'', 111–154
PDF
* ; 2009: Taxonomic revision and biogeography of the ''Tamarix''-feeding ''Diorhabda elongata'' (Brullé, 1832) species group (Coleoptera: Chrysomelidae: Galerucinae: Galerucini) and analysis of their potential in biological control of Tamarisk. ''Zootaxa'', 2101: 1-152
PDF
* ; ; 1996: ''Economic Insect Fauna of China, Fasc. 54, Coleoptera: Chrysomeloidea (II).'' Science Press, Beijing, China, 324 pp. (In Chinese)
* 1893: Chrysomelidae. In: Erichson, W. (ED.), ''Naturgeschichte der Insecten Deutschland'', 61(73): 961–1161. (In German)
* 2005: ''Program for Biological Control of Saltcedar (Tamarix spp.) in Thirteen States: Environmental Assessment.'' USDA APHIS, Fort Collins, Colorado. 56 pp
PDF

Notes

External links

*
* Center for Biological Diversity 17 June 2009 press release regarding lawsuit to protect the southwestern willow flycatcher in view of defoliation of tamarisk nesting habitat by ''D. carinulata''

* Montana War on Weeds information on ''D. carinulata'' (not ''D. elongata'') for tamarisk biocontrol

* Tamarisk Coalition information on tamarisk biocontrol (China and Kazakhstan source tamarisk beetles are ''D. carinulata''

* University of California Berkeley Campus News article on initial 2001 release of ''D. carinulata'' (not ''D. elongata'')

* USDA/ARS research with ''D. carinulata'' (not ''D. elongata'') for tamarisk biocontrol in Wyoming and Montana

* USDA/ARS and Texas Agri-Life Research and Extension Service Report of Information to the Public; ''Progress on Biological Control of Saltcedar in the Western U.S.: EmphasisTexas 2004–2009.'
PDF

{{Taxonbar, from=Q1650121

Galerucinae
Biological pest control beetles
Insects used for control of invasive plants
Insects of Mongolia
Beetles described in 1870