Editing Biological pest control (section)

==Biological control agents==

===Predators===
[[File:Chrysopidae 3035.jpg|thumb|left|[[Predator]]y [[Chrysopidae|lacewings]] are available from biocontrol dealers.]]

Predators are mainly free-living species that directly consume a large number of [[prey]] during their whole lifetime. Given that many major crop pests are insects, many of the predators used in biological control are insectivorous species. [[Ladybugs|Lady beetles]], and in particular their larvae which are active between May and July in the northern hemisphere, are voracious predators of [[aphid]]s, and also consume [[mites]], [[scale insect]]s and small [[caterpillar]]s. The spotted lady beetle (''[[Coleomegilla maculata]]'') is also able to feed on the eggs and larvae of the [[Colorado potato beetle]] (''Leptinotarsa decemlineata'').<ref>{{cite book |author=Acorn, John |title=Ladybugs of Alberta: Finding the Spots and Connecting the Dots |url=https://archive.org/details/ladybugsofalbert00acor |url-access=registration |year=2007 |publisher=University of Alberta |isbn=978-0-88864-381-0 |page=[https://archive.org/details/ladybugsofalbert00acor/page/15 15]}}</ref>

The larvae of many [[hoverfly]] species principally feed upon [[aphid]]s, one larva devouring up to 400 in its lifetime. Their effectiveness in commercial crops has not been studied.<ref>{{cite web |title=Know Your Friends. Hover Flies |url=http://www.entomology.wisc.edu/mbcn/kyf211.html |publisher=University of Wisconsin |access-date=7 June 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160604163106/http://www.entomology.wisc.edu/mbcn/kyf211.html |archive-date=4 June 2016 }}</ref>

The running crab spider ''[[Philodromus cespitum]]'' also prey heavily on aphids, and act as a biological control agent in European fruit orchards.<ref>Michalko, Radek; Dvoryankina, Viktoriya (1 June 2019). "Intraspecific phenotypic variation in functional traits of a generalist predator in an agricultural landscape". ''Agriculture, Ecosystems & Environment''. '''278''': 35–42. [[Doi (identifier)|doi]]:10.1016/j.agee.2019.03.018.</ref>

[[File:Organic-agriculture biocontrol-cotton polistes-wasp3.png|thumb|[[Predator]]y ''[[Paper wasp|Polistes]]'' [[Vespid|wasp]] searching for bollworms or other [[caterpillar]]s on a cotton plant]]

Several species of [[entomopathogenic nematode]] are important predators of insect and other invertebrate pests.<ref>{{cite book |author=Kaya, Harry K. |chapter=An Overview of Insect-Parasitic and Entomopathogenic Nematodes |editor=Bedding, R.A. |title=Nematodes and the Biological Control of Insect Pests |publisher=CSIRO Publishing |year=1993 |isbn=978-0-643-10591-1 |chapter-url=https://books.google.com/books?id=drhdg7UmNnAC&pg=PT8 |pages=8–12 |display-authors=etal |url-status=live |archive-url=https://web.archive.org/web/20160512141401/https://books.google.com/books?id=drhdg7UmNnAC&pg=PT8 |archive-date=12 May 2016}}</ref><ref name=Capinera1992>{{Cite journal |last1=Capinera |first1=John L. |last2=Epsky |first2=Nancy D. |date=1992-01-01 |title=Potential for Biological Control of Soil Insects in the Caribbean Basin Using Entomopathogenic Nematodes |journal=The Florida Entomologist |volume=75 |issue=4 |pages=525–532 |jstor=3496134 |doi=10.2307/3496134}}</ref> Entomopathogenic nematodes form a stress–resistant stage known as the infective juvenile. These spread in the soil and infect suitable insect hosts. Upon entering the insect they move to the [[hemolymph]] where they recover from their stagnated state of development and release their [[Photorhabdus|bacterial]] [[Symbiosis|symbionts]]. The bacterial symbionts reproduce and release toxins, which then kill the host insect.<ref name=Capinera1992/><ref name=Campos2015>{{cite book |title=Nematode Pathogenesis of insects and other pests |date=2015 |publisher=Springer |isbn=978-3-319-18266-7 |edition=1 |pages=4–6, 31–32 |last=Campos |first=Herrera R. |editor1-first=Raquel |editor1-last=Campos-Herrera |doi=10.1007/978-3-319-18266-7|hdl=11586/145351 |s2cid=27605492 }}</ref> ''[[Phasmarhabditis hermaphrodita]]'' is a microscopic [[nematode]] that kills slugs. Its complex life cycle includes a free-living, infective stage in the soil where it becomes associated with a pathogenic bacteria such as ''[[Moraxella osloensis]]''. The nematode enters the slug through the posterior mantle region, thereafter feeding and reproducing inside, but it is the bacteria that kill the slug. The nematode is available commercially in Europe and is applied by watering onto moist soil.<ref>{{cite web |url=http://www.biocontrol.entomology.cornell.edu/pathogens/phasmarhabditis.php |title=Biological control: ''Phasmarhabditis hermaphrodita'' |publisher=Cornell University |access-date=15 June 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160618025012/http://www.biocontrol.entomology.cornell.edu/pathogens/phasmarhabditis.php |archive-date=18 June 2016 }}</ref> Entomopathogenic nematodes have a limited [[shelf life]] because of their limited resistance to high temperature and dry conditions.<ref name=Campos2015/> The type of soil they are applied to may also limit their effectiveness.<ref name=Capinera1992/>

Species used to control spider mites include the predatory mites ''[[Phytoseiulus persimilis]]'',<ref>{{cite web |title=Glasshouse red spider mite |url=https://www.rhs.org.uk/advice/profile?PID=190 |publisher=[[Royal Horticultural Society]] |access-date=7 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160614161933/https://www.rhs.org.uk/advice/profile?PID=190 |archive-date=14 June 2016 }}</ref> ''[[Neoseilus]] [[Neoseilus californicus|californicus]],''<!--aka Amblyseius--><ref name=UConnMites/> and ''[[Amblyseius]] [[Amblyseius cucumeris|cucumeris]]'', the predatory midge ''[[Feltiella acarisuga]]'',<ref name=UConnMites>{{cite web |title=Biological Control of Two- Spotted Spider Mites |url=http://ipm.uconn.edu/documents/raw2/html/664.php?aid=664 |publisher=University of Connecticut |access-date=7 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160807023211/http://ipm.uconn.edu/documents/raw2/html/664.php?aid=664 |archive-date= 7 August 2016 }}</ref> and a ladybird ''[[Stethorus punctillum]]''.<ref name=UConnMites/> The bug ''[[Orius insidiosus]]'' has been successfully used against the [[Tetranychus urticae|two-spotted spider mite]] and the [[western flower thrips]] (''Frankliniella occidentalis'').<ref>{{cite book |author=Xuenong Xu |title=Combined Releases of Predators for Biological Control of Spider Mites ''Tetranychus urticae'' Koch and Western Flower Thrips ''Frankliniella occidentalis'' (Pergande) |url=https://books.google.com/books?id=y6DGyV7HmqAC&pg=PA37 |year=2004 |publisher=Cuvillier Verlag |isbn=978-3-86537-197-3 |page=37}}</ref>

Predators including ''Cactoblastis cactorum'' (mentioned above) can also be used to destroy invasive plant species. As another example, the [[Agonopterix alstroemeriana|poison hemlock moth]] (''Agonopterix alstroemeriana)'' can be used to control [[Conium maculatum|poison hemlock]] (''Conium maculatum''). During its larval stage, the moth strictly consumes its host plant, poison hemlock, and can exist at hundreds of larvae per individual host plant, destroying large swathes of the hemlock.<ref>{{Cite journal |last1=Castells |first1=Eva |last2=Berenbaum |first2=May R. |date=June 2006 |title=Laboratory Rearing of Agonopterix alstroemeriana, the Defoliating Poison Hemlock (Conium maculatum L.) Moth, and Effects of Piperidine Alkaloids on Preference and Performance |journal=Environmental Entomology |volume=35 |issue=3 |pages=607–615 |doi=10.1603/0046-225x-35.3.607|s2cid=45478867 |url=https://ddd.uab.cat/pub/artpub/2006/125702/2006_alstroemeriana_rearing.pdf }}</ref>

[[File:Aleiodes indiscretus wasp parasitizing gypsy moth caterpillar.jpg|thumb|The [[parasitoid wasp]] ''[[Aleiodes|Aleiodes indiscretus]]'' parasitizing a [[spongy moth]] caterpillar, a serious pest of forestry<ref>{{cite web | url=http://sfec.cfans.umn.edu/prod/groups/cfans/@pub/@cfans/@sfec/documents/article/cfans_article_380545.pdf | title=European Gypsy Moth (Lymantria dispar) | access-date=3 December 2017 | url-status=dead | archive-url=https://web.archive.org/web/20130517073305/http://sfec.cfans.umn.edu/prod/groups/cfans/@pub/@cfans/@sfec/documents/article/cfans_article_380545.pdf | archive-date=17 May 2013}}</ref>]]

For [[Rodent#As pests and disease vectors|rodent pests]], [[Farm cat|cat]]s are effective biological control when used in conjunction with reduction of [[Refuge (ecology)|"harborage"/hiding]] locations.<ref>{{cite journal |title=The Use of Food as a Buffer in a Predator-Prey System |first=David E. |last=Davis |date=20 November 1957 |journal=Journal of Mammalogy |volume=38 |issue=4 |pages=466–472 |doi=10.2307/1376399 |jstor=1376399 }}</ref><ref name="Lambert">{{cite thesis |type=PhD |last1=Lambert |first1=Mark |title=Control Of Norway Rats In The Agricultural Environment: Alternatives To Rodenticide Use |url=https://lra.le.ac.uk/bitstream/2381/27745/1/2003LambertMSPhD.pdf |publisher=University of Leicester |pages=85–103 |format=Thesis |date=September 2003 |access-date=2017-11-11 |archive-date=2017-11-11 |archive-url=https://web.archive.org/web/20171111151737/https://lra.le.ac.uk/bitstream/2381/27745/1/2003LambertMSPhD.pdf |url-status=dead }}</ref><ref name="Wodzicki">{{cite journal |title=Prospects for biological control of rodent populations |first=Kazimierz |last=Wodzicki |date=11 November 1973 |journal=Bulletin of the World Health Organization |volume=48 |issue=4 |pages=461–467 |pmid=4587482 |pmc=2481104}}</ref> While cats are effective at preventing rodent [[Irruptive growth|"population explosions"]], they are not effective for eliminating pre-existing severe infestations.<ref name="Wodzicki"/> [[Western barn owl|Barn owls]] are also sometimes used as biological rodent control.<ref name=Charter>{{cite web |url=http://www.owls.org/conservation/ewExternalFiles/barn_owls_in_israel.pdf |title=Using barn owls (''Tyto alba erlangeri'') for biological pest control in Israel |author=Charter, Motti |publisher=World Owl Trust |access-date=11 November 2017 |archive-url=https://web.archive.org/web/20171111095113/http://www.owls.org/conservation/ewExternalFiles/barn_owls_in_israel.pdf |archive-date=2017-11-11 |url-status=dead }}</ref> Although there are no quantitative studies of the effectiveness of barn owls for this purpose,<ref>{{cite journal |title=Are avian predators effective biological control agents for rodent pest management in agricultural systems? |first1=Lushka |last1=Labuschagne |first2=Lourens H. |last2=Swanepoel |first3=Peter J |last3=Taylor |first4=Steven R. |last4=Belmain |first5=Mark |last5=Keith |date=1 October 2016 |journal=Biological Control |volume=101 |issue=Supplement C |pages=94–102 |doi=10.1016/j.biocontrol.2016.07.003|bibcode=2016BiolC.101...94L |url=http://gala.gre.ac.uk/15648/23/15648%20BELMAIN_Avian_Predators_13-06-2016.pdf |hdl=10019.1/111721 |hdl-access=free }}</ref> they are known rodent predators that can be used in addition to or instead of cats;<ref>{{Cite book|url=https://books.google.com/books?id=4ddfAQAAQBAJ&pg=PA141 |title=Crop Protection in Medieval Agriculture: Studies in pre-modern organic agriculture |first=Jan C. |last=Zadoks | author-link=Jan Zadoks|date=16 October 2013 |publisher=Sidestone Press |access-date=11 November 2017 |via=Google Books|isbn=9789088901874 }}</ref><ref>{{cite web |url=https://attra.ncat.org/how_can_i_control_rodents_organically/ |title=How can I control rodents organically? |publisher=ATTRA - National Sustainable Agriculture Information Service |access-date=11 November 2017 |archive-date=17 October 2021 |archive-url=https://web.archive.org/web/20211017132940/https://attra.ncat.org/how_can_i_control_rodents_organically/ |url-status=dead }}</ref> they can be encouraged into an area with nest boxes.<ref>{{cite journal |title=Agricultural land use, barn owl diet, and vertebrate pest control implications |first1=Sara M. |last1=Kross |first2=Ryan P. |last2=Bourbour |first3=Breanna L. |last3=Martinico |date=1 May 2016 |journal=Agriculture, Ecosystems & Environment |volume=223 |issue=Supplement C |pages=167–174 |doi=10.1016/j.agee.2016.03.002|bibcode=2016AgEE..223..167K }}</ref><ref>{{cite web |url=https://www.barnowltrust.org.uk/barn-owl-facts/barn-owl-home-range/ |title=Barn Owl home range |publisher=The Barn Owl Trust |access-date=11 November 2017}}</ref>

In Honduras, where the mosquito ''[[Aedes aegypti]]'' was transmitting [[dengue fever]] and other infectious diseases, biological control was attempted by a community action plan; [[copepod]]s, baby [[turtle]]s, and juvenile [[tilapia]] were added to the wells and tanks where the mosquito breeds and the mosquito larvae were eliminated.<ref>{{cite web |url=http://ecotippingpoints.org/our-stories/indepth/honduras-community-eradication-aedes-aegypti-dengue-zika.html |title=The Monte Verde Story (Honduras): Community Eradication of Aedes aegypti (the mosquito responsible for Zika, dengue fever, and chikungunya) |author= Marten, Gerry; Caballero, Xenia; Romero, Hilda; Larios, Arnulfo |date=1 January 2019 |publisher=The EcoTipping Point Project  |access-date=30 January 2020}}</ref>

Even amongst arthropods usually thought of as obligate [[predator]]s of animals (especially other arthropods), [[flower|floral]] food sources ([[nectar]] and to a lesser degree [[pollen]]) are often useful adjunct sources.<ref name="He-et-al-2021" /> It had been noticed in one study<ref name="He-Sigsgaard-2019" /> that adult ''[[Adalia bipunctata]]'' (predator and common biocontrol of ''[[Mediterranean flour moth|Ephestia kuehniella]]'') could survive on flowers but never completed its [[biological life cycle|life cycle]], so a meta-analysis<ref name="He-et-al-2021" /> was done to find such an overall trend in previously published data, if it existed. In some cases floral resources are outright necessary.<ref name="He-et-al-2021" /> Overall, floral resources (and an imitation, i.e. sugar water) increase [[longevity]] and [[fecundity]], meaning even predatory population numbers can depend on non-prey food abundance.<ref name="He-et-al-2021" /> Thus biocontrol population maintenance – and success – may depend on nearby flowers.<ref name="He-et-al-2021" />

===Parasitoids===
{{main|Parasitoid}}

Parasitoids lay their eggs on or in the body of an insect host, which is then used as a food for developing larvae. The host is ultimately killed. Most insect [[parasitoid]]s are [[Parasitoid wasp|wasps]] or [[Fly|flies]], and many have a very narrow host range. The most important groups are the [[Ichneumonidae|ichneumonid wasps]], which mainly use [[caterpillar]]s as hosts; [[Braconidae|braconid wasps]], which attack caterpillars and a wide range of other insects including aphids; [[chalcid wasp|chalcidoid wasps]], which parasitize eggs and larvae of many insect species; and [[Tachinidae|tachinid flies]], which parasitize a wide range of insects including caterpillars, [[beetle]] adults and larvae, and [[Hemiptera|true bugs]].<ref>{{cite web|title=Parasitoid Wasps (Hymenoptera) |url=https://extension.umd.edu/hgic/insects/parasitoid-wasps-hymenoptera |publisher=University of Maryland |access-date=6 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160827072031/https://extension.umd.edu/hgic/insects/parasitoid-wasps-hymenoptera |archive-date=27 August 2016}}</ref> Parasitoids are most effective at reducing pest populations when their host organisms have limited [[refuge (ecology)|refuges]] to hide from them.<ref name="HawkinsThomas1993">{{cite journal |last1=Hawkins |first1=B. A. |last2=Thomas |first2=M. B. |last3=Hochberg |first3=M. E. |title=Refuge Theory and Biological Control |journal=Science |volume=262 |issue=5138 |year=1993 |pages=1429–1432 |doi=10.1126/science.262.5138.1429 |pmid=17736826|bibcode=1993Sci...262.1429H |s2cid=45268030 }}</ref>

[[File:Encarsia formosa, an endoparasitic wasp, is used for whitefly control.jpg|thumb|''[[Encarsia formosa]]'', widely used in [[greenhouse]] horticulture, was one of the first biological control agents developed.]]
[[File:Waspcycle.png|thumb|right|450px|Life cycles of greenhouse whitefly and its parasitoid wasp ''[[Encarsia formosa]]'']]

Parasitoids are among the most widely used biological control agents. Commercially, there are two types of rearing systems: short-term daily output with high production of parasitoids per day, and long-term, low daily output systems.<ref name=smith>{{cite journal |author=Smith, S.M. |date=1996 |title=Biological control with Trichogramma: advances, successes, and potential of their use |journal=Annual Review of Entomology |volume=41 |pages=375–406 |pmid=15012334 |doi=10.1146/annurev.en.41.010196.002111}}</ref> In most instances, production will need to be matched with the appropriate release dates when susceptible host species at a suitable phase of development will be available.<ref>{{cite journal |author1= Knoll, Valery |author2=Ellenbroek, Thomas |author3=Romeis, Jörg |author4=Collatz, Jana  |year=2017 |title=Seasonal and regional presence of hymenopteran parasitoids of ''Drosophila'' in Switzerland and their ability to parasitize the invasive ''Drosophila suzukii'' |journal=Scientific Reports |volume=7 |issue=40697 |pages=40697 |doi=10.1038/srep40697 |pmid=28098183 |pmc=5241644 |bibcode=2017NatSR...740697K }}</ref> Larger production facilities produce on a yearlong basis, whereas some facilities produce only seasonally. Rearing facilities are usually a significant distance from where the agents are to be used in the field, and transporting the parasitoids from the point of production to the point of use can pose problems.<ref>{{cite book|author1=Sithanantham, S. |author2=Ballal, Chandish R. |author3=Jalali, S.K. |author4=Bakthavatsalam, N. |title=Biological Control of Insect Pests Using Egg Parasitoids |url=https://books.google.com/books?id=cCO4BAAAQBAJ&pg=PA246 |year=2013 |publisher=Springer |isbn=978-81-322-1181-5 |page=246 |url-status=live |archive-url=https://web.archive.org/web/20170410133425/https://books.google.com/books?id=cCO4BAAAQBAJ&pg=PA246 |archive-date=10 April 2017}}</ref> Shipping conditions can be too hot, and even vibrations from planes or trucks can adversely affect parasitoids.<ref name=smith/>

''[[Encarsia formosa]]'' is a small parasitoid wasp attacking [[whitefly|whiteflies]], sap-feeding insects which can cause wilting and [[Sooty mold|black sooty moulds]] in glasshouse vegetable and ornamental crops. It is most effective when dealing with low level infestations, giving protection over a long period of time. The wasp lays its eggs in young whitefly 'scales', turning them black as the parasite larvae pupate.<ref name=Hoddle1998>{{cite journal |title=Biology and Use of the Whitefly Parasitoid Encarsia Formosa |author1=Hoddle, M. S. |author2=Van Driesche, R. G. |author3=Sanderson, J. P. |date=1998 |journal=Annual Review of Entomology |volume=43 |pages=645–669 |doi=10.1146/annurev.ento.43.1.645 |pmid=15012401 }}</ref> ''[[Gonatocerus ashmeadi]]'' ([[Hymenoptera]]: [[Mymaridae]]) has been introduced to control the [[glassy-winged sharpshooter]] ''Homalodisca vitripennis'' (Hemiptera: [[Cicadellidae]]) in [[French Polynesia]] and has successfully controlled ~95% of the pest density.<ref name=Hoddle2006>{{cite journal |author1=Hoddle M. S. |author2=Grandgirard J. |author3=Petit J. |author4=Roderick G. K. |author5=Davies N. | year=2006 | title=Glassy-winged sharpshooter Ko'ed – First round – in French Polynesia | journal=Biocontrol News and Information | volume=27 | issue=3 | pages=47N–62N}}</ref>

The [[Choristoneura fumiferana|eastern spruce budworm]] is an example of a destructive insect in [[fir]] and [[spruce]] forests. Birds are a natural form of biological control, but the ''Trichogramma minutum'', a species of parasitic wasp, has been investigated as an alternative to more controversial chemical controls.<ref name="smith2">{{Cite journal | doi=10.1111/j.1439-0418.1986.tb00830.x|title = Factors affecting inundative releases of ''Trichogramma'' minutum ''Ril''. Against the Spruce Budworm| journal=Journal of Applied Entomology| volume=101| issue=1–5| pages=29–39|year = 1986|last1 = Smith|first1 = S. M.| last2=Hubbes| first2=M.| last3=Carrow| first3=J. R.|s2cid = 84398725}}</ref>

There are a number of recent studies pursuing sustainable methods for controlling urban cockroaches using parasitic wasps.<ref>{{cite journal |last1=Bressan-Nascimento |first1=S. |last2=Oliveira |first2=D.M.P. |last3=Fox |first3=E.G.P. |title=Thermal requirements for the embryonic development of Periplaneta americana (L.) (Dictyoptera: Blattidae) with potential application in mass-rearing of egg parasitoids |journal=Biological Control |date=December 2008 |volume=47 |issue=3 |pages=268–272 |doi=10.1016/j.biocontrol.2008.09.001|bibcode=2008BiolC..47..268B }}</ref><ref>{{cite journal |last1=Paterson Fox |first1=Eduardo Gonçalves |last2=Bressan-Nascimento |first2=Suzete |last3=Eizemberg |first3=Roberto |title=Notes on the Biology and Behaviour of the Jewel Wasp, Ampulex compressa (Fabricius, 1781) (Hymenoptera; Ampulicidae), in the Laboratory, Including First Record of Gregarious Reproduction |journal=Entomological News |date=September 2009 |volume=120 |issue=4 |pages=430–437 |doi=10.3157/021.120.0412|s2cid=83564852 }}</ref> Since most cockroaches remain in the sewer system and sheltered areas which are inaccessible to insecticides, employing active-hunter wasps is a strategy to try and reduce their populations.

===Pathogens===
{{Further|Biopesticide}}

Pathogenic micro-organisms include [[bacteria]], [[fungi]], and [[viruses]]. They kill or debilitate their host and are relatively host-specific. Various [[microbial]] insect diseases occur naturally, but may also be used as [[biological pesticide]]s.<ref>[http://ec.europa.eu/environment/integration/research/newsalert/pdf/134na5.pdf Encouraging innovation in biopesticide development.] {{webarchive |url=https://web.archive.org/web/20120515143828/http://ec.europa.eu/environment/integration/research/newsalert/pdf/134na5.pdf |date=15 May 2012}} European Commission (2008). Accessed on 9 January 2017</ref> When naturally occurring, these outbreaks are density-dependent in that they generally only occur as insect populations become denser.<ref>{{cite book |author1=Huffaker, C. B. |author2=Berryman, A. A. |author3=Laing, J. E. |date=1984 |chapter=Natural control of insect populations |pages=[https://archive.org/details/ecologicalentomo0000unse/page/359 359–398] |editor=C. B. Huffaker and R. L. Rabb |title=Ecological Entomology |publisher=Wiley Interscience |isbn=978-0-471-06493-0 |chapter-url=https://archive.org/details/ecologicalentomo0000unse |url=https://archive.org/details/ecologicalentomo0000unse/page/359 }}</ref>

The use of pathogens against [[aquatic weed]]s was unknown until a groundbreaking 1972 proposal by Zettler and Freeman. Up to that point biocontrol of any kind had not been used against any water weeds. In their review of the possibilities, they noted the lack of interest and information thus far, and listed what was known of pests-of-pests – whether pathogens or not. They proposed that this should be relatively straightforward to apply in the same way as other biocontrols.<ref name="Zettler-Freeman-1972">{{cite journal | last1=Zettler | first1=F W | last2=Freeman | first2=T E | title=Plant Pathogens as Biocontrols of Aquatic Weeds | journal=[[Annual Review of Phytopathology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=10 | issue=1 | year=1972 | issn=0066-4286 | doi=10.1146/annurev.py.10.090172.002323 | pages=455–470| bibcode=1972AnRvP..10..455Z }}</ref> And indeed in the decades since, the same biocontrol methods that are routine on land have become common in the water.

====Bacteria====

Bacteria used for biological control infect insects via their digestive tracts, so they offer only limited options for controlling insects with sucking mouth parts such as aphids and scale insects.<ref>{{cite book |author=Swan, L.A. |date=1964 |title=Beneficial Insects |url=https://archive.org/details/beneficialinsect0000swan |url-access=registration |page= [https://archive.org/details/beneficialinsect0000swan/page/249 249]|publisher=New York, Harper & Row }}</ref> ''[[Bacillus thuringiensis]]'', a soil-dwelling bacterium, is the most widely applied species of bacteria used for biological control, with at least four sub-species used against [[Lepidoptera]]n ([[moth]], [[butterfly]]), [[Coleoptera]]n (beetle) and [[Diptera]]n (true fly) insect pests. The bacterium is available to organic farmers in sachets of dried spores which are mixed with water and sprayed onto vulnerable plants such as [[brassica]]s and [[fruit tree]]s.<ref name=Lemaux>{{cite journal |doi=10.1146/annurev.arplant.58.032806.103840 |title=Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part I) |year=2008 |last1=Lemaux |first1=Peggy G. |journal=Annual Review of Plant Biology |volume=59 |issue=1 |pages=771–812 |pmid=18284373|bibcode=2008AnRPB..59..771L }}</ref><ref name=McGaughey>{{cite journal | last1 = McGaughey | first1 = W. H. | last2 = Gould | first2 = F. | last3 = Gelernter | first3 = W. | year = 1998 | title = Bt resistance management | journal = Nat. Biotechnol. | volume = 16 | issue = 2| pages = 144–6 | doi = 10.1038/nbt0298-144 | pmid = 9487517 | s2cid = 37947689 }}</ref> [[Gene]]s from ''B. thuringiensis'' have also been incorporated into [[Genetically modified crops|transgenic crops]], making the plants express some of the bacterium's toxins, which are [[protein]]s. These confer resistance to insect pests and thus reduce the necessity for pesticide use.<ref name=Kumar>{{Cite book| last1=Kumar | first1=PA | last2=Malik | first2=VS | last3=Sharma | first3=RP | year=1996 | title=Insecticidal proteins of Bacillus thuringiensis | journal=Advances in Applied Microbiology | volume=42 | pages=1–43 | doi=10.1016/S0065-2164(08)70371-X | pmid=8865583 | isbn=9780120026425  | url=https://zenodo.org/record/1259743 }}</ref> If pests develop resistance to the toxins in these crops, ''B. thuringiensis'' will become useless in organic farming also.<ref>{{cite web|last1=Neppl |first1=Camilla |title=Management of Resistance to Bacillus thuringiensis Toxins |url=http://camillapede.tripod.com/bapaper.html |date=26 May 2000 |url-status=live |archive-url=https://web.archive.org/web/20170421000124/http://camillapede.tripod.com/bapaper.html |archive-date=21 April 2017 }}</ref><ref name=McGaughey/>
The bacterium ''[[Paenibacillus popilliae]]'' which causes [[Milky spore|milky spore disease]] has been found useful in the control of [[Japanese beetle]], killing the larvae. It is very specific to its host species and is harmless to vertebrates and other invertebrates.<ref>{{cite web|url=http://www.biocontrol.entomology.cornell.edu/pathogens/paenibacillus.php |title=Biological control: ''Paenibacillus popilliae'' |publisher=Cornell University |access-date=15 June 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160621024151/http://www.biocontrol.entomology.cornell.edu/pathogens/paenibacillus.php |archive-date=21 June 2016 }}</ref>

''[[Bacillus]]'' spp.,<ref group="M" name="biocontrol-MoAs">p.{{nbs}}94-5, II. Biocontrol Modes of Action</ref> [[fluorescent Pseudomonad]]s,<ref group="M" name="biocontrol-MoAs" /> and [[Streptomycete]]s are controls of various fungal pathogens.<ref group="M" name="intro-examples-agents">p.{{nbs}}94</ref>

==== Colombia mosquito control ====
The largest-ever deployment of ''[[Wolbachia]]''-infected ''A. aegypti'' mosquitoes reduced dengue incidence by 94–97% in the Colombian cities of [[Bello, Antioquia|Bello]], [[Medellín]], and [[Itagüí]]. The project was executed by non-profit World Mosquito Program (WMP). Wolbachia prevents mosquitos from transmitting viruses such as dengue and [[zika]]. The insects pass the bacteria on to their offspring. The project covered a combined area of {{Convert|135|km2}}, home to 3.3 million people. Most of the project area reached the target of infecting 60% of local mosquitoes. The technique is not endorsed by WHO.<ref>{{Cite journal |last=Lenharo |first=Mariana |date=2023-10-27 |title=Dengue rates drop after release of modified mosquitoes in Colombia |url=https://www.nature.com/articles/d41586-023-03346-2 |journal=Nature |volume=623 |issue=7986 |pages=235–236 |language=en |doi=10.1038/d41586-023-03346-2|pmid=37891252 |bibcode=2023Natur.623..235L |s2cid=264543032 }}</ref>

=== Fungi ===
[[File:Pandora neoaphidis.jpg|thumb|right|[[Green peach aphid]], a pest in its own right and a vector of plant viruses, killed by the fungus ''[[Pandora neoaphidis]]'' ([[Zygomycota]]: [[Entomophthorales]]) Scale bar = 0.3 mm.]]

[[Entomopathogenic fungi]], which cause disease in insects, include at least 14 species that attack [[aphid]]s.<ref>{{cite journal |author1=Hall, I.M. |author2=Dunn, P.H.  |title=Entomophthorous Fungi Parasitic on the Spotted Alfalfa Aphid |journal=Hilgardia |date=1957 |volume=27 |issue=4 |pages=159–181 |doi=10.3733/hilg.v27n04p159|doi-access=free }}</ref> ''[[Beauveria bassiana]]'' is mass-produced and used to manage a wide variety of insect pests including [[whiteflies]], [[thrips]], aphids and [[weevils]].<ref name=McNeil>{{cite web|last1=McNeil |first1=Jim |title=Fungi for the biological control of insect pests |url=http://articles.extension.org/pages/18928/fungi-for-the-biological-control-of-insect-pests |publisher=eXtension.org |access-date=6 June 2016 |date=2016 |url-status=live |archive-url=https://web.archive.org/web/20160526163616/http://articles.extension.org/pages/18928/fungi-for-the-biological-control-of-insect-pests |archive-date=26 May 2016 }}</ref> ''[[Lecanicillium]]'' spp. are deployed against white flies, thrips and aphids. ''[[Metarhizium]]'' spp. are used against pests including beetles, [[locusts]] and other grasshoppers, [[Hemiptera]], and [[spider mite]]s. ''[[Paecilomyces fumosoroseus]]'' is effective against white flies, thrips and aphids; ''[[Purpureocillium]] lilacinus'' is used against [[root-knot nematodes]], and 89 ''[[Trichoderma]]'' [[List of Trichoderma species|species]] against certain plant pathogens.<ref group="M" name="Trichoderma">p.{{nbs}}93</ref> ''[[Trichoderma viride]]'' has been used against [[Dutch elm disease]], and has shown some effect in suppressing [[Chondrostereum purpureum|silver leaf]], a disease of stone fruits caused by the pathogenic fungus ''[[Chondrostereum purpureum]]''.<ref name=Fry>{{cite book |author=Fry, William E.|title=Principles of Plant Disease Management |url=https://books.google.com/books?id=n1kxOTitCAgC&pg=PA187 |year=2012 |publisher=Academic Press |isbn=978-0-08-091830-3 |page=187}}</ref>

Pathogenic fungi may be controlled by other fungi, or bacteria or yeasts, such as: ''[[Gliocladium]]'' spp., [[mycoparasite|mycoparasitic]] ''[[Pythium]]'' spp., [[binucleate]] types of ''[[Rhizoctonia]]'' spp., and ''[[Laetisaria]]'' spp.

The fungi ''[[Cordyceps]]'' and ''[[Metacordyceps]]'' are deployed against a wide spectrum of arthropods.<ref>{{cite journal |author1=Santhosh, Kumar T. |author2=Aparna, N. S. |title=Cordyceps Species as a Bio-Control Agent against Coconut Root Grub, Leucopholis coneophora Burm |journal=Journal of Environmental Research and Development |volume=8 |issue=3A |date=2014 |pages=614–618 |url=https://www.jerad.org/ppapers/dnload.php?vl=8&is=3A&st=614 |access-date=2017-03-20 |archive-date=2018-10-04 |archive-url=https://web.archive.org/web/20181004085356/https://www.jerad.org/ppapers/dnload.php?vl=8&is=3A&st=614 |url-status=dead }}</ref> ''[[Entomophaga (fungus)|Entomophaga]]'' is effective against pests such as the [[Myzus persicae|green peach aphid]].<ref name=Capinera>{{cite web|url=http://entnemdept.ufl.edu/creatures/veg/aphid/green_peach_aphid.htm |title=Featured creatures: Peach Aphid |last=Capinera |first=John L. |date=October 2005 |website=University of Florida – Department of Entomology and Nematology |publisher=University of Florida |access-date=7 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160526234842/http://entnemdept.ufl.edu/creatures/veg/aphid/green_peach_aphid.htm |archive-date=26 May 2016 }}</ref>

Several members of [[Chytridiomycota]] and [[Blastocladiomycota]] have been explored as agents of biological control.<ref name=Li>{{cite journal | last1=Li | first1=Z. | last2=Dong | first2=Q. | last3=Albright | first3=T.P. | last4=Guo | first4=Q. | year=2011 | title=Natural and human dimensions of a quasi-natural wild species: the case of kudzu | journal=Biological Invasions | volume=13 | issue=10 | pages=2167–2179 | doi=10.1007/s10530-011-0042-7| s2cid=14948770 }}</ref><ref name=Frog>{{cite journal | last1 = Beard | first1 = Karen H. | last2 = O'Neill | first2 = Eric M. | year = 2005 | title = Infection of an invasive frog ''Eleutherodactylus coqui'' by the chytrid fungus ''Batrachochytrium dendrobatidis'' in Hawaii | doi = 10.1016/j.biocon.2005.07.004 | journal = Biological Conservation | volume = 126 | issue = 4| pages = 591–595 | bibcode = 2005BCons.126..591B | url = https://works.bepress.com/karenh_beard/106/download/ }}</ref><!--<ref name=Sparrow1960>{{cite book |author=Sparrow, F.K. |date=1960 |title=Aquatic Phycomyetes |publisher=University of Michigan Press |edition=2nd }}</ref>--> From Chytridiomycota, ''[[Synchytrium|Synchytrium solstitiale]]'' is being considered as a control agent of the [[Centaurea solstitialis|yellow star thistle]] (''Centaurea solstitialis'') in the United States.<ref name=Gleason>{{cite book |author1=Voigt K. |author2=Marano, A. V. |author3=Gleason, F. H.  |date=2013 |title=Ecological & Economical Importance of Parasitic Zoosporic True Fungi |work=The Mycota: A Comprehensive Treatise on Fungi as Experimental Systems for Basic & Applied Research Vol. 11 Agricultural Applications |edition=2nd |editor=K. Esser & F. Kempken |publisher=Springer |pages=243–270}}</ref>

====Viruses====
[[Baculoviridae|Baculoviruses]] are specific to individual insect host species and have been shown to be useful in [[Viral biological control|viral biological pest control]]. For example, the [[Lymantria dispar multicapsid nuclear polyhedrosis virus]] has been used to spray large areas of forest in North America where larvae of the [[Lymantria dispar dispar|spongy moth]] are causing serious defoliation. The moth larvae are killed by the virus they have eaten and die, the disintegrating cadavers leaving virus particles on the foliage to infect other larvae.<ref>{{cite web |author=D'Amico, Vince |url=https://biocontrol.entomology.cornell.edu/pathogens/baculoviruses.php |title=Biological control: Baculoviruses |publisher=Cornell University  |access-date=15 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160601063135/http://www.biocontrol.entomology.cornell.edu/pathogens/baculoviruses.php |archive-date=1 June 2016}}</ref>

A mammalian virus, the [[rabbit haemorrhagic disease virus]] was introduced to Australia to attempt to control the [[European rabbit]] populations there.<ref>{{cite journal|last1=Abrantes |first1=Joana |last2=van der Loo |first2=Wessel |last3=Le Pendu |first3=Jacques |last4=Esteves |first4=Pedro J. |title=Rabbit haemorrhagic disease (RHD) and rabbit haemorrhagic disease virus (RHDV): a review |journal=Veterinary Research |date=2012 |volume=43 |issue=12 |pages=12 |doi=10.1186/1297-9716-43-12 |pmid=22325049 |pmc=3331820 |doi-access=free }}</ref> It escaped from quarantine and spread across the country, killing large numbers of rabbits. Very young animals survived, passing immunity to their offspring in due course and eventually producing a virus-resistant population.<ref>{{cite web |url=http://www.csiro.au/Outcomes/Food-and-Agriculture/RCDFactsheet.aspx |format=pdf |title=Rabbit Calicivirus Disease (RCD) |last=Strive |first=Tanja |publisher=[[Commonwealth Scientific and Industrial Research Organisation]] |date=16 July 2008 |access-date=8 April 2017 |url-status=dead |archive-url=https://web.archive.org/web/20140415081441/http://www.csiro.au/Outcomes/Food-and-Agriculture/RCDFactsheet.aspx |archive-date=April 15, 2014 }}</ref> Introduction into New Zealand in the 1990s was similarly successful at first, but a decade later, immunity had developed and populations had returned to pre-RHD levels.<ref>{{cite news |title=Plan for 1080 drops in MacKenzie Basin |url=http://www.stuff.co.nz/the-press/news/2441711/Mackenzie-1080-drop-plan |last=Williams |first=David |date=26 May 2009 |newspaper=The Press |access-date=8 April 2017}}</ref>
{{further|Rabbits in Australia}}

RNA [[mycovirus]]es are controls of various fungal pathogens.<ref group="M" name="intro-examples-agents" />

==== Oomycota ====
''[[Lagenidium]] [[Lagenidium giganteum|giganteum]]'' is a water-borne mold that parasitizes the larval stage of mosquitoes. When applied to water, the motile spores avoid unsuitable host species and search out suitable mosquito larval hosts. This mold has the advantages of a dormant phase, resistant to desiccation, with slow-release characteristics over several years. Unfortunately, it is susceptible to many chemicals used in mosquito abatement programmes.<ref>{{cite web |url=https://biocontrol.entomology.cornell.edu/pathogens/lagenidium.php |title=Biological control: ''Lagenidium giganteum'' |author=Kerwin, James L. |publisher=Cornell University |access-date=15 June 2016 |url-status=dead |archive-date=20 June 2016 |archive-url=https://web.archive.org/web/20160620032211/http://www.biocontrol.entomology.cornell.edu/pathogens/lagenidium.php}}</ref>

===Competitors===
The [[legume]] vine ''[[Mucuna pruriens]]'' is used in the countries of [[Benin]] and [[Vietnam]] as a biological control for problematic ''[[Imperata cylindrica]]'' grass: the vine is extremely vigorous and suppresses neighbouring plants by [[Competition (biology)|out-competing]] them for space and light. ''Mucuna pruriens'' is said not to be invasive outside its cultivated area.<ref name="tropical">{{Cite web |url=http://www.tropicalforages.info/key/Forages/Media/Html/Mucuna_pruriens.htm |title=Factsheet – Mucuna pruriens |publisher=Tropical Forages |access-date=21 May 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080515210229/http://www.tropicalforages.info/key/Forages/Media/Html/Mucuna_pruriens.htm |archive-date=15 May 2008 }}</ref> ''[[Desmodium]] [[Desmodium uncinatum|uncinatum]]'' can be used in [[push-pull technology|push-pull farming]] to stop the [[parasitic plant]], witchweed (''[[Striga (plant)|Striga]]'').<ref>{{Cite journal | last1=Khan | first1=Z. | last2=Midega | first2=C. A. O. | last3=Amudavi | first3=D. M.  | last4=Hassanali | first4=A.| last5=Pickett | first5=J. A. | title=On-farm evaluation of the 'push–pull' technology for the control of stemborers and striga weed on maize in western Kenya| journal=Field Crops Research| volume=106| issue=3| pages=224–233| year=2008| doi=10.1016/j.fcr.2007.12.002| bibcode=2008FCrRe.106..224K }}</ref>

The Australian bush fly, ''[[Musca vetustissima]]'', is a major nuisance pest in Australia, but native decomposers found in Australia are not adapted to feeding on cow dung, which is where bush flies breed. Therefore, the [[Australian Dung Beetle Project]] (1965–1985), led by [[George Bornemissza]] of the [[Commonwealth Scientific and Industrial Research Organisation]], released forty-nine species of [[dung beetle]], to reduce the amount of dung and therefore also the potential breeding sites of the fly.<ref name="adbp">{{cite journal | last1=Bornemissza | first1=G. F. | year=1976 | title=The Australian dung beetle project 1965–1975 | journal=Australian Meat Research Committee Review | volume=30 | pages=1–30 }}</ref>

===Combined use of parasitoids and pathogens===

In cases of massive and severe infection of invasive pests, techniques of pest control are often used in combination. An example is the [[emerald ash borer]], ''[[Agrilus planipennis]]'', an invasive [[beetle]] from [[China]], which has destroyed tens of millions of [[ash trees]] in its introduced range in [[North America]]. As part of the campaign against it, from 2003 American scientists and the Chinese Academy of Forestry searched for its natural enemies in the wild, leading to the discovery of several parasitoid wasps, namely ''Tetrastichus planipennisi'', a gregarious larval endoparasitoid, ''[[Oobius agrili]]'', a solitary, parthenogenic egg parasitoid, and ''[[Spathius agrili]]'', a gregarious larval ectoparasitoid. These have been introduced and released into the [[United States|United States of America]] as a possible biological control of the emerald ash borer. Initial results for ''Tetrastichus planipennisi'' have shown promise, and it is now being released along with ''[[Beauveria bassiana]]'', a fungal [[pathogen]] with known insecticidal properties.<ref name="APHIS">{{Cite journal |last=Gould |first=Juli |author2=Bauer, Leah |title=Biological Control of Emerald Ash Borer (''Agrilus planipennis'') |url=http://www.aphis.usda.gov/plant_health/plant_pest_info/emerald_ash_b/downloads/eab-biocontrol.pdf |publisher=United States Department of Agriculture |access-date=28 April 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110110005023/http://www.aphis.usda.gov/plant_health/plant_pest_info/emerald_ash_b/downloads/eab-biocontrol.pdf |archive-date=10 January 2011 }}</ref><ref name="Bauer et al">{{cite journal|last1=Bauer |first1=L.S. |last2=Liu |first2=H.-P. |last3=Miller |first3=D. |last4=Gould |first4=J. |year=2008 |title=Developing a classical biological control program for Agrilus planipennis (Coleoptera: Buprestidae), an invasive ash pest in North America |journal=Newsletter of the Michigan Entomological Society |volume=53 |issue=3&4 |pages=38–39 |url=http://www.nrs.fs.fed.us/pubs/jrnl/2008/nrs_2008_bauer_002.pdf |access-date=29 April 2011 |url-status=live |archive-url=https://web.archive.org/web/20111004090830/http://www.nrs.fs.fed.us/pubs/jrnl/2008/nrs_2008_bauer_002.pdf |archive-date= 4 October 2011}}</ref><ref name="ScienceDaily">{{Cite web |url=https://www.sciencedaily.com/releases/2011/04/110426111415.htm |title=Biocontrol: Fungus and Wasps Released to Control Emerald Ash Borer |date=26 April 2011 |website=Science News |publisher=ScienceDaily |access-date=27 April 2011 |url-status=live |archive-url=https://web.archive.org/web/20110504012056/https://www.sciencedaily.com/releases/2011/04/110426111415.htm |archive-date=4 May 2011}}</ref>

=== Secondary plants ===

In addition, biological pest control sometimes makes use of plant defenses to reduce crop damage by herbivores. Techniques include [[polyculture]], the planting together of two or more species such as a primary crop and a secondary plant, which may also be a crop. This can allow the secondary plant's defensive chemicals to protect the crop planted with it.<ref name="Parolin Bresch 2012">{{cite journal | last1=Parolin | first1=Pia | last2=Bresch | first2=Cécile | last3=Desneux | first3=Nicolas | last4=Brun | first4=Richard | last5=Bout | first5=Alexandre | last6=Boll | first6=Roger | last7=Poncet | first7=Christine | title=Secondary plants used in biological control: A review | journal=International Journal of Pest Management | volume=58 | issue=2 | year=2012 | doi=10.1080/09670874.2012.659229 | pages=91–100}}</ref>