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'{{italic title}} {{Taxobox | name = ''Trichogramma'' | regnum = [[Animal]]ia | phylum = [[Arthropod]]a | classis = [[Insect]]a | ordo = [[Hymenoptera]] | subordo = [[Apocrita]] | superfamilia = [[Chalcidoidea]] | familia = [[Trichogrammatidae]] | genus = ''''' Trichogramma ''''' | subdivision_ranks = Species | subdivision = 230+, see text }} '''''Trichogramma''''' are minute [[polyphagous]] wasps that are [[endoparasitoid]]s of insect eggs.<ref name=flanders>{{cite journal | last1 = Flanders | first1 = S | last2 = Quednau | first2 = W | year = 1960 | title = Taxonomy of the genus ''Trichogramma'' (Hymenoptera, Chalcidoidea, Trichogrammatidae) | url = | journal = BioControl | volume = 5 | issue = | pages = 285–294 | doi=10.1007/bf02372951}}</ref> ''Trichogramma'' is one of around 80 genera from the family [[Trichogrammatidae]], with over 200 species worldwide.<ref name=consoli>Consoli FL, Parra JRP, Zucchi RA (2010) 'Egg Parasitoids in Agroecosystems with Emphasis on Trichogramma.' (Springer).</ref><ref name=knutson>Knutson A (2005) 'The ''Trichogramma'' Manual: A guide to the use of ''Trichogramma'' for Biological Control with Special Reference to Augmentative Releases for Control of Bollworm and Budworm in Cotton.' (Texas Agricultural Extension Service).</ref><ref name=sumer>{{cite journal | last1 = Sumer | first1 = F | last2 = Tuncbilek | first2 = AS | last3 = Oztemiz | first3 = S | last4 = Pintureau | first4 = B | last5 = Rugman-Jones | first5 = P | last6 = Stouthamer | first6 = R | year = 2009 | title = A molecular key to the common species of ''Trichogramma'' of the Mediterranean region | url = | journal = BioControl | volume = 54 | issue = | pages = 617–624 | doi=10.1007/s10526-009-9219-8}}</ref> Although there are several groups of egg parasitoids commonly employed for [[biological control]] throughout the world, ''Trichogramma'' have been the most extensively studied.<ref name=upadhay>Upadhyay RK, Mukerji KG, Chamola BP (2001) 'Biocontrol potential and its Exploitation in Sustainable Agriculture: Insect Pests.' (Kluwer Academic/ Plenum Publishers).</ref> There have been more than a thousand papers published on ''Trichogramma'' and they are the most used biological control agents in the world.<ref name=knuston>Knutson A (2005) 'The Trichogramma Manual: A guide to the use of Trichogramma for Bilogical Control with Special Reference to Augmentative Releases for Control of bollworm and Budworm in Cotton.' (Texas Agricultural Extension Service).</ref> Trichogramma are unique to the size limit of how small an insect can be, which would be determined by how few neurons they can fit in their central nervous system, yet exhibit a complex behavior to sustain their life. Trichogramma have less than 10,000 neurons, which is a hundred times fewer than the next smallest insect.<ref>[http://www.mymultiplesclerosis.co.uk/wonders/trichogramma.html Macademia Nut Plantation, Trichogramma]</ref> == Parasitism == To locate host eggs, adult females use chemical and visual signals, such as egg shape and colour.<ref name=knuston/> After she finds a suitable egg, an experienced female will attempt to determine if the egg has previously been parasitized using using her ovipositor and antennal drumming (tapping on the egg surface). Females also use antennal drumming to determine the size and quality of the target egg, which determines the number of eggs the female will insert.<ref>{{cite journal |last= Klomp |first=H |last2=Teerink |first2=B.J.|last3=Wei |first3=Chun Ma |date=1979 |title=Discrimination Between Parasitized and Unparasitized Hosts in the Egg Parasite ''Trichogramma embryophagum'' (Hym.=Trichogrammatidae)=a Matter of Learning and Forgetting |url=http://booksandjournals.brillonline.com/content/journals/10.1163/002829679x00412 |journal=Netherlands Journal of Zoology |publisher= Koninklijke Brill NV |volume=30 |issue=2 |pages=254–27 |DOI=10.1163/002829679X00412 |ISSN=0028-2960 |accessdate=May 22, 2014}}</ref> A single female can parasitize one to ten host eggs a day. == Identification == ''Trichogramma'' are small and very uniform in structure which causes difficulty in identifying the separate species.<ref name=nag>{{cite journal | last1 = Nagarkatti | first1 = S | last2 = Nagaraja | first2 = H | year = 1977 | title = Biosystematics of ''Trichogramma'' and ''Trichogrammatoidea'' species | url = | journal = Annual Review of Entomology | volume = 22 | issue = | pages = 157–176 | doi=10.1146/annurev.en.22.010177.001105}}</ref><ref name=thomson>{{cite journal | last1 = Thomson | first1 = LJ | last2 = Rundle | first2 = BJ | last3 = Carew | first3 = ME | last4 = Hoffmann | first4 = AA | year = 2003 | title = Identification and characterization of ''Trichogramma'' species from south-eastern Australia using the internal transcribed spacer 2 (ITS-2) region of the ribosomal gene complex | url = | journal = Entomologia Experimentalis et Applicata | volume = 106 | issue = | pages = 235–240 | doi=10.1046/j.1570-7458.2003.00029.x}}</ref> As females are all relatively similar, taxonomists rely upon examination of males to tell the different species apart using features of their antennae and genitalia.<ref name=nagar>{{cite journal | last1 = Nagarkatti | first1 = S | last2 = Nagaraja | first2 = H | year = 1971 | title = Redescriptions of some known species of ''Trichogramma'' (Hym., Trichogrammatidae), showing the importance of the male genitalia as a diagnostic character | url = | journal = Bulletin of Entomological Research | volume = 61 | issue = | pages = 13–31 | doi=10.1017/s0007485300057412}}</ref><ref name=polaszek>{{cite journal | last1 = Polaszek | first1 = A | last2 = Rugman-Jones | first2 = P | last3 = Stouthamer | first3 = R | last4 = Hernandez-Suarez | first4 = E | last5 = Cabello | first5 = T | last6 = Pino Pérez | first6 = M | year = 2012 | title = Molecular and morphological diagnoses of five species of ''Trichogramma'': biological control agents of ''Chrysodeixis chalcites'' (Lepidoptera: Noctuidae) and ''Tuta absoluta'' (Lepidoptera: Gelechiidae) in the Canary Islands | url = | journal = BioControl | volume = 57 | issue = | pages = 21–35 | doi=10.1007/s10526-011-9361-y}}</ref> The first description of a ''Trichogramma'' species was in North America in 1871 by Charles V. Riley. He described the tiny wasps that emerged from eggs of the Viceroy butterfly as ''Trichogramma minutum''.<ref name=knutson/> In [[Taxonomy (biology)|taxonomy]], original specimens are very important as they are the basis of reference for subsequent descriptions of species. The original specimens, however, were lost. Riley also described a second species in 1879 as ''Trichogramma pretiosum'', but these specimens were also lost. To correct these errors, entomologists returned to the areas where Riley originally found the species and obtained neotype specimens of ''T. minutum'' and ''T. pretiosum''. These specimens are now preserved properly in the [[United States National Museum]].<ref name=knutson/> Currently the number of ''Trichogramma'' species is over 200 but as of 1960 only some 40 species of ''Trichogramma'' had been described.<ref>[http://www.nhm.ac.uk/research-curation/research/projects/chalcidoids/]</ref> ==Wolbachia in Trichogramma== [[Wolbachia]] is a widespread bacterium that alters the host’s reproductive success. Horizontal transfer of ''Wolbachia'' has been observed in many arthropods in vitro and in nature.<ref name = Grenier>{{cite journal | last1 = Grenier | first1 = Simon, et al. | year = 1998 | title = Successful horizontal transfer of ''Wolbachia'' symbionts between Trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 265 | pages = 1441–1445}}</ref><ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> Horizontal transfer of parthenogenesis-inducing ''Wolbachia'' occurs in ''Trichogramma'' wasps in nature.<ref name=Bourtzis>{{cite journal | last1= Bourtzis | first1 = Kostas | last2= O'Neill | first2= Scott | year = 1998 | title = ''Wolbachia'' Infections and Arthropod Reproduction | journal = Bioscience | volume = 48 | pages = 287–293}}</ref> [[Parthenogenesis]] is a form of asexual reproduction that occurs without fertilization. Parthenogenesis-inducing ''Wolbachia'' has been observed to cause infected females to asexually produce fertile females and nonfunctional males .<ref name=Bourtzis>{{cite journal | last1= Bourtzis | first1 = Kostas | last2= O'Neill | first2= Scott | year = 1998 | title = ''Wolbachia'' Infections and Arthropod Reproduction | journal = Bioscience | volume = 48 | pages = 287–293}}</ref> This may lead to the speciation of ''Trichogramma'' if ''Wolbachia'' is maintained long enough for genetic divergence to occur and a new species of asexual producing wasps become reproductively isolated. <ref name=Bourtzis>{{cite journal | last1= Bourtzis | first1 = Kostas | last2= O'Neill | first2= Scott | year = 1998 | title = ''Wolbachia'' Infections and Arthropod Reproduction | journal = Bioscience | volume = 48 | pages = 287–293}}</ref> Horizontal transfer of ''Wolbachia'' has been observed within the same species and among different species of ''Trichogramma'', including ''T. kaykai'', ''T. deion, T. pretiosum, T. atopovirilia''; however, interspecial horizontal transfer of ''Wolbachia'' and it's evolutionary implications are not well understood .<ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> In-vitro, successful horizontal transfer is uncommon.<ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> This may be due to the fact that for parthenogenesis induction by horizontal transfer to occur, the density of ''Wolbachia'' must be high inside of the host’s ovaries. <ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> Cytoplasmic incompatibility of the host and bacterium can also be the source of this unsuccessful transfer. <ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> These limitations in-vitro suggest that in nature, horizontal transfer by parthenogenesis- inducing ''Wolbachia'' may be a difficult and rare phenomenon. However, when looking at the Wolbachia-host associations, the ''Trichogramma-Wolbachia'' form a monophletic group based on several ''Wolbachia''-specific genes, which may be explained by horizontal transfer of Wolbachia between different species.<ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> Therefore, although interspecific horizontal transfer of ''Wolbachia'' is limited in-vitro, it is likely to occur quite frequently in nature. ===Evolutionary Implications of ''Wolbachia'' in ''Trichogramma''=== Through mechanisms such as parthenogenesis and horizontal transfer, ''Wolbachia'' may contribute to the speciation of ''Trichogramma'' populations. Understanding interspatial horizontal transfer will help uncover the mechanism behind manipulation of the host’s genome. Through alteration of the host’s genome, new genetic variation arises and is spread to other hosts within close proximity. Parthenogenesis produces nonfunctional males that are reproductively isolated from females, which may also lead to speciation by producing new asexual species.<ref name=Huigens>{{cite journal | last1 = Huigens | first1 = M. E. et al. | year = 2004 | title = Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducing wolbachia in trichogramma wasps | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 271 | pages = 509–515}}</ref> Commonly, uninfected individuals are unable to breed with infected individuals. <ref name=":0">{{Cite journal|title = Evolutionary consequences of Wolbachia infections|url = http://www.ncbi.nlm.nih.gov/pubmed/12683975|journal = Trends in genetics: TIG|date = 2003-04-01|issn = 0168-9525|pmid = 12683975|pages = 217-223|volume = 19|issue = 4|doi = 10.1016/S0168-9525(03)00024-6|first = Sylvain|last = Charlat|first2 = Gregory D. D.|last2 = Hurst|first3 = Hervé|last3 = Merçot}}</ref> Many generations of reproductive isolation of these different groups may result in speciation.<ref name=":0">{{Cite journal|title = Evolutionary consequences of Wolbachia infections|url = http://www.ncbi.nlm.nih.gov/pubmed/12683975|journal = Trends in genetics: TIG|date = 2003-04-01|issn = 0168-9525|pmid = 12683975|pages = 217-223|volume = 19|issue = 4|doi = 10.1016/S0168-9525(03)00024-6|first = Sylvain|last = Charlat|first2 = Gregory D. D.|last2 = Hurst|first3 = Hervé|last3 = Merçot}}</ref> In addition, some hosts can evolve with a dependency on ''Wolbachia'' for core reproductive functions such as oogenesis, so that eventually an infection is a requirement for successful reproduction.<ref name=":0" /> Finally, ''Wolbachia'' can influence gender determination in its hosts so that more females are successfully born. This results in a reversal in sexual selection where females must compete for male mates. Female sexual selection leads to evolution, as it exposes different phenotypes to natural selection.<ref name=":0" /> == Biological control == ''Trichogramma'' have been used for control of lepidopteran pests for many years. They can be considered the ''Drosophila'' of the parasitoid world as they have been used for inundative releases and much of our understanding today comes from experiments with these wasps.<ref name=smith>Smith SM (1996) Biological control with Trichogramma: advances, successes, and potential of their use. In 'Annual Review of Entomology' pp. 375-406.</ref> Entomologists in the early 1900s began to rear ''Trichogramma'' for biological control. ''Trichogramma minutum'' is one of the most commonly found species in Europe and was first mass reared in 1926 on eggs of ''[[Sitotroga cerealella]]''.<ref name=flanders>{{cite journal | last1 = Flanders | first1 = SE | year = 1930 | title = Mass Production of Egg Parasites of the Genus ''Trichogramma'' | url = | journal = Hilgardia | volume = 4 | issue = | pages = 465–501 | doi=10.3733/hilg.v04n16p465}}</ref> Nine species of ''Trichogramma'' are produced commercially in insectaries around the world with 30 countries releasing them. ''Trichogramma'' are used for control on numerous crops and plants, these include cotton, sugarcane, vegetables, sugar beets, orchards and forests.<ref name=hassan>{{cite journal | last1 = Hassan | first1 = SA | year = 1993 | title = The mass rearing and utilization of ''Trichogramma'' to control lepidopterous pests: Achievements and outlook | url = | journal = Pesticide Science | volume = 37 | issue = | pages = 387–391 | doi=10.1002/ps.2780370412}}</ref> Some of the pests that are controlled include Cotton bollworm (''[[Helicoverpa armigera]]''), Codling moth (''[[Cydia pomonella]]''), Lightbrown apple moth (''[[Epiphyas postvittana]]''), and European corn borer (''[[Ostrinia nubilalis]]''). ''Trichogramma'' species vary in their host specificity. This can lead to non-target hosts being parasitized. This can cause problems by reducing the amount of parasitism of the target host, and depending on the rate of parasitism, non-target effects could be significant on non-target host populations. === Species used === The most commonly used species for biological control are ''[[Trichogramma atopovirilia|T. atopovirilia]]'', ''[[Trichogramma brevicapillum|T. brevicapillum]]'', ''[[Trichogramma deion|T. deion]]'', ''[[Trichogramma exiguum|T. exiguum]]'', ''[[Trichogramma fuentesi|T. fuentesi]]'', ''[[Trichogramma minutum|T. minutum]]'', ''[[Trichogramma nubilale|T. nubilale]]'', ''[[Trichogramma platneri|T. platneri]]'', ''[[Trichogramma pretiosum|T. pretiosum]]'' and ''[[Trichogramma thalense|T. thalense]]''.<ref name=knutson/> ==''Trichogramma pretiosum''== ''[[Trichogramma pretiosum]]'' is the most widely distributed ''Trichogramma'' species in North America.<ref name=knutson/> It has been the focus of many research studies and has been able to be reared on 18 genera of Lepidoptera. It is a more generalized parasitoid, able to parasitise a range of different species. ''T. pretiosum'' was introduced into Australia in the 1970s as part of the Ord River Irrigation Area (ORIA) IPM scheme.<ref name=davies>{{cite journal | last1 = Davies | first1 = AP | last2 = Zalucki | first2 = MP | year = 2008 | title = Collection of ''Trichogramma'' Westwood (Hymenoptera: Trichogrammatidae) from tropical northern Australia: a survey of egg parasitoids for potential pest insect biological control in regions of proposed agricultural expansion | url = | journal = Australian Journal of Entomology | volume = 47 | issue = | pages = 160–167 | doi=10.1111/j.1440-6055.2008.00644.x}}</ref><ref name=davieset>{{cite journal | last1 = Davies | first1 = AP | last2 = Pufke | first2 = US | last3 = Zalucki | first3 = MP | year = 2011 | title = Spatio-temporal variation in ''Helicoverpa'' egg parasitism by ''Trichogramma'' in a tropical Bt-transgenic cotton landscape | url = | journal = Agricultural and Forest Entomology | volume = 13 | issue = | pages = 247–258 | doi=10.1111/j.1461-9563.2010.00512.x}}</ref> ==''Trichogramma carverae''== ''[[Trichogramma carverae]]'' are mainly used for [[light brown apple moth]] and [[codling moth]] control and is predominately used in orchards.<ref name=llewellyn>Llewellyn R (2002) ''The good bug book: beneficial organisms commercially available in Australia and New Zealand for biological pest control.' (Integrated Pest Management Pty Ltd).</ref> In Australia ''T. carverae'' is used for biological control of light brown apple moth in vineyards. Though Australia has its own native ''Trichogramma'' species there has not been much work undertaken to commercially use them for biological control within Australia.<ref name=glenn>{{cite journal | last1 = Glenn | first1 = DC | last2 = Hercus | first2 = MJ | last3 = Hoffmann | first3 = AA | year = 1997 | title = Characterizing ''Trichogramma'' (Hymenoptera: Trichogrammatidae) species for biocontrol of light brown apple moth (Lepidoptera: Tortricidae) in grapevines in Australia | url = | journal = Annals of the Entomological Society of America | volume = 90 | issue = | pages = 128–137 }}</ref> Light brown apple moth is common throughout Australia and is polyphagous on more than 80 native and introduced species. The larvae are the stage that causes the most damage, especially to grape berries which provides sites for bunch rot to occur.<ref>{{cite journal | last1 = Glenn | first1 = DC | last2 = Hoffmann | first2 = AA | year = 1997 | title = Developing a commercially viable system for biological control of light brown apple moth (Lepidoptera: Tortricidae) in grapes using endemic ''Trichogramma'' (Hymenoptera: Trichogrammatidae) | url = | journal = Journal of Economic Entomology | volume = 90 | issue = | pages = 370–382 }}</ref> Losses in the crops can amount up to $2000/ha in one season. It is very predominant in areas like the Yarra Valley. Insecticide use is not a preferred method by most growers who prefer a more natural mean of controlling pests. As a result, ''Trichogramma'' were considered a good candidate for biological control as the larvae are difficult to control with insecticide and light brown apple moths are relatively vulnerable to egg parasitism with their eggs being laid in masses of 20-50 on the upper surfaces of basal leaves in grapevines. == Selected Species == * ''[[Trichogramma aomoriense]]'' * ''[[Trichogramma atopovirilia]]'' * ''[[Trichogramma brassicae]]'' * ''[[Trichogramma brevicapillum]]'' * ''[[Trichogramma carverae]]'' * ''[[Trichogramma chilonis]]'' * ''[[Trichogramma deion]]'' * ''[[Trichogramma dendrolimi]]'' * ''[[Trichogramma evanescens]]'' * ''[[Trichogramma exiguum]]'' * ''[[Trichogramma falx]]'' * ''[[Trichogramma fuentesi]]'' * ''[[Trichogramma funiculatum]]'' * ''[[Trichogramma japonicum]]'' * ''[[Trichogramma maori]]'' * ''[[Trichogramma minutum]]'' * ''[[Trichogramma nubilale]]'' * ''[[Trichogramma papilonis]]'' * ''[[Trichogramma platneri]]'' * ''[[Trichogramma pretiosum]]'' * ''[[Trichogramma siddiqi]]'' * ''[[Trichogramma thalense]]'' * ''[[Trichogramma valentinei]]'' * ''[[Trichogramma yawarae]]'' == References == {{Reflist}} == External links == {{wikispecies}} * [http://insects.tamu.edu/extension/bulletins/b-6071.html#trichogramma Biocontrol-oriented ''Trichogramma'' Manual] * [http://www.dpi.qld.gov.au/cropresearch/16030.html ''Trichogramma'' Article] [[Category:Trichogrammatidae]] [[Category:Pest insects biological control agents]] [[Category:Biological pest control wasps]]'