![Cotesia9061](https://upload.wikimedia.org/wikipedia/commons/7/7f/Cotesia9061.8.15.07.c.jpg)
Biological control or biocontrol is a method of
controlling pests, such as
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s,
mite
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
s,
weed
A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...
s, and
plant diseases
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungus, fung ...
,
using other organisms. It relies on
predation
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
,
parasitism
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
,
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 ...
, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of
integrated pest management
Integrated pest management (IPM), also known as integrated pest control (IPC) is a broad-based approach that integrates both chemical and non-chemical practices for economic control of pests. IPM aims to suppress pest populations below the econ ...
(IPM) programs.
There are three basic strategies for biological pest control: classical (importation), where a natural enemy of a pest is introduced in the hope of achieving control; inductive (augmentation), in which a large population of natural enemies are administered for quick pest control; and inoculative (conservation), in which measures are taken to maintain natural enemies through regular reestablishment.
Natural enemies of insect pests, also known as biological control agents, include predators,
parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s,
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
s, and
competitors
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators,
herbivore
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 ...
s, and plant pathogens.
Biological control can have side-effects on
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
through attacks on non-target species by any of the above mechanisms, especially when a species is introduced without a thorough understanding of the possible consequences.
History
The term "biological control" was first used by
Harry Scott Smith
Harry Scott Smith (November 29, 1883 – November 28, 1957), an entomologist and professor at University of California, Riverside (UCR), was a pioneer in the field of biological pest control.
United States Department of Agriculture
Smith gre ...
at the 1919 meeting of the Pacific Slope Branch of the American Association of Economic Entomologists, in
Riverside, California
Riverside is a city in and the county seat of Riverside County, California, United States, in the Inland Empire metropolitan area. It is named for its location beside the Santa Ana River. It is the most populous city in the Inland Empire an ...
. It was brought into more widespread use by the entomologist Paul H. DeBach (1914–1993) who worked on citrus crop pests throughout his life. However, the practice has previously been used for centuries. The first report of the use of an insect species to control an insect pest comes from "
Nanfang Caomu Zhuang
The (c. 304 CE) ''Nanfang caomu zhuang'' (南方草木狀 ''Plants of the Southern Regions''), attributed to the Western Jin dynasty scholar and botanist Ji Han (嵇含, 263-307), is a Flora describing the plants of Nanyue and Jiaozhi, pres ...
" (南方草木狀 ''Plants of the Southern Regions'') (), attributed to
Western Jin dynasty
Western may refer to:
Places
*Western, Nebraska, a village in the US
*Western, New York, a town in the US
*Western Creek, Tasmania, a locality in Australia
*Western Junction, Tasmania, a locality in Australia
*Western world, countries that id ...
botanist ''Ji Han'' (嵇含, 263–307), in which it is mentioned that "''
Jiaozhi
Jiaozhi (standard Chinese, pinyin: ''Jiāozhǐ''), or Giao Chỉ (Vietnamese), was a historical region ruled by various Chinese dynasties, corresponding to present-day northern Vietnam. The kingdom of Nanyue (204–111 BC) set up the Jiaozhi Co ...
people sell ants and their nests attached to twigs looking like thin cotton envelopes, the reddish-yellow ant being larger than normal. Without such ants, southern citrus fruits will be severely insect-damaged''".
The ants used are known as ''huang gan'' (''huang'' = yellow, ''gan'' = citrus) ants (''
Oecophylla smaragdina
''Oecophylla smaragdina'' ( common names include Asian weaver ant, weaver ant, green ant, green tree ant, semut rangrang, semut kerangga, and orange gaster) is a species of arboreal ant found in tropical Asia and Australia. These ants form colon ...
''). The practice was later reported by Ling Biao Lu Yi (late
Tang Dynasty
The Tang dynasty (, ; zh, t= ), or Tang Empire, was an Dynasties in Chinese history, imperial dynasty of China that ruled from 618 to 907 AD, with an Zhou dynasty (690–705), interregnum between 690 and 705. It was preceded by the Sui dyn ...
or Early
Five Dynasties
The Five Dynasties and Ten Kingdoms period (), from 907 to 979, was an era of political upheaval and division in 10th-century Imperial China. Five dynastic states quickly succeeded one another in the Central Plain, and more than a dozen conc ...
), in ''Ji Le Pian'' by ''Zhuang Jisu'' (
Southern Song Dynasty
The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the rest ...
), in the ''Book of Tree Planting'' by Yu Zhen Mu (
Ming Dynasty
The Ming dynasty (), officially the Great Ming, was an Dynasties in Chinese history, imperial dynasty of China, ruling from 1368 to 1644 following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming dynasty was the last ort ...
), in the book ''Guangdong Xing Yu'' (17th century), ''Lingnan'' by Wu Zhen Fang (Qing Dynasty), in ''Nanyue Miscellanies'' by Li Diao Yuan, and others.
Biological control techniques as we know them today started to emerge in the 1870s. During this decade, in the US, the Missouri State Entomologist C. V. Riley and the Illinois State Entomologist W. LeBaron began within-state redistribution of parasitoids to control crop pests. The first international shipment of an insect as a biological control agent was made by Charles V. Riley in 1873, shipping to France the predatory mites ''Tyroglyphus phylloxera'' to help fight the grapevine phylloxera (
''Daktulosphaira vitifoliae'') that was destroying grapevines in France. The
United States Department of Agriculture
The United States Department of Agriculture (USDA) is the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...
(USDA) initiated research in classical biological control following the establishment of the Division of Entomology in 1881, with C. V. Riley as Chief. The first importation of a parasitoidal wasp into the United States was that of the braconid ''
Cotesia glomerata
''Cotesia glomerata'', the white butterfly parasite, is a small parasitoid wasp species belonging to family Braconidae. It was first described by Carl Linnaeus in his 1758 publication 10th edition of Systema Naturae.
Description
The adults ...
'' in 1883–1884, imported from Europe to control the invasive cabbage white butterfly, ''
Pieris rapae
''Pieris rapae'' is a small- to medium-sized butterfly species of the whites-and-yellows family Pieridae. It is known in Europe as the small white, in North America as the cabbage white or cabbage butterfly, on several continents as the small ca ...
''. In 1888–1889 the vedalia beetle, ''
Rodolia cardinalis'', a lady beetle, was introduced from
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 ...
to
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
to control the cottony cushion scale, ''
Icerya purchasi
''Icerya purchasi'' ( common name: cottony cushion scale) is a scale insect that feeds on more than 80 families of woody plants, most notably on ''Citrus'' and ''Pittosporum''. Originally described in 1878 from specimens collected in New Zealand ...
''. This had become a major problem for the newly developed citrus industry in California, but by the end of 1889, the cottony cushion scale population had already declined. This great success led to further introductions of beneficial insects into the US.
[Coulson, J. R.; Vail, P. V.; Dix M.E.; Nordlund, D.A.; Kauffman, W.C.; Eds. 2000. 110 years of biological control research and development in the United States Department of Agriculture: 1883–1993. U.S. Department of Agriculture, Agricultural Research Service. pages=3–11]
In 1905 the USDA initiated its first large-scale biological control program, sending entomologists to Europe and Japan to look for natural enemies of the spongy moth, ''
Lymantria dispar dispar
''Lymantria dispar dispar'' or LDD moth, commonly known as the gypsy moth, European gypsy moth, North American gypsy moth, or spongy moth, is a species of moth in the family Erebidae that is of Eurasian origin. It has a range that extends over E ...
'', and the brown-tail moth,
''Euproctis chrysorrhoea'', invasive pests of trees and shrubs. As a result, nine parasitoids (solitary wasps) of the spongy moth, seven of the brown-tail moth, and two predators of both moths became established in the US. Although the spongy moth was not fully controlled by these natural enemies, the frequency, duration, and severity of its outbreaks were reduced and the program was regarded as successful. This program also led to the development of many concepts, principles, and procedures for the implementation of biological control programs.
[
]
Prickly pear cacti
''Opuntia'', commonly called prickly pear or pear cactus, is a genus of flowering plants in the cactus family Cactaceae. Prickly pears are also known as ''tuna'' (fruit), ''sabra'', ''nopal'' (paddle, plural ''nopales'') from the Nahuatl word f ...
were introduced into 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 as ornamental plants, starting in 1788. They quickly spread to cover over 25 million hectares of Australia by 1920, increasing by 1 million hectares per year. Digging, burning, and crushing all proved ineffective. Two control agents were introduced to help control the spread of the plant, the cactus moth '' Cactoblastis cactorum'', and the scale insect ''Dactylopius
''Dactylopius'' is a genus of insect in the superfamily Coccoidea, the scale insects. It is the only genus in the family Dactylopiidae.Van Dam, A. R. and B. May. (2012)A new species of ''Dactylopius'' Costa (''Dactylopius gracilipilus'' sp. nov.) ...
''. Between 1926 and 1931, tens of millions of cactus moth eggs were distributed around Queensland with great success, and by 1932, most areas of prickly pear had been destroyed.
The first reported case of a classical biological control attempt in Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
involves the parasitoidal wasp ''Trichogramma
''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (2010 ...
minutum''. Individuals were caught in New York State
New York, officially the State of New York, is a state in the Northeastern United States. It is often called New York State to distinguish it from its largest city, New York City. With a total area of , New York is the 27th-largest U.S. stat ...
and released in Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
gardens in 1882 by William Saunders, a trained chemist and first Director of the Dominion Experimental Farms, for controlling the invasive currantworm '' Nematus ribesii''. Between 1884 and 1908, the first Dominion Entomologist, James Fletcher, continued introductions of other parasitoids and pathogens for the control of pests in Canada.
Types of biological pest control
There are three basic biological pest control strategies: importation (classical biological control), augmentation and conservation.
Importation
Importation or classical biological control involves the introduction of a pest's natural enemies to a new locale where they do not occur naturally. Early instances were often unofficial and not based on research, and some introduced species became serious pests themselves.
To be most effective at controlling a pest, a biological control agent requires a colonizing ability which allows it to keep pace with changes to the habitat in space and time. Control is greatest if the agent has temporal persistence so that it can maintain its population even in the temporary absence of the target species, and if it is an opportunistic forager, enabling it to rapidly exploit a pest population.
One of the earliest successes was in controlling ''Icerya purchasi
''Icerya purchasi'' ( common name: cottony cushion scale) is a scale insect that feeds on more than 80 families of woody plants, most notably on ''Citrus'' and ''Pittosporum''. Originally described in 1878 from specimens collected in New Zealand ...
'' (cottony cushion scale) in Australia, using a predatory insect '' Rodolia cardinalis'' (the vedalia beetle). This success was repeated in California using the beetle and a parasitoidal fly, ''Cryptochaetum
''Cryptochetum'' is a genus of scale parasite flies in the family Cryptochetidae. There are more than 30 described species in ''Cryptochetum''.
Species
These 35 species belong to the genus ''Cryptochetum'':
*''Cryptochetum acuticornutum, C. acu ...
iceryae''. Other successful cases include the control of ''Antonina graminis
''Antonina graminis'' or Rhodes grass scale is a species of mealybug in the family Pseudococcidae. In the 1940s the species, originating in Asia, infested nearly 69 species fodder and turf grasses in Texas causing major economic loss. Classical b ...
'' in Texas by ''Neodusmetia sangwani
''Neodusmetia sangwani'' is an encyrtid parasitoid from India that was used in classical biological control of the Rhodesgrass Scale, ''Antonina graminis'' (Maskell) (Pseudococcidae) which is a major pest of grasses outside of its native range in ...
'' in the 1960s.
Damage from ''Hypera postica
''Hypera postica'', commonly known as the alfalfa weevil, is a species of beetle in the superfamily Curculionoidea; it can be found in alfalfa fields throughout Europe. Considered a destructive threat to alfalfa production in North America, sev ...
'', the alfalfa weevil, a serious introduced pest of forage, was substantially reduced by the introduction of natural enemies. 20 years after their introduction the population of weevil
Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...
s in the alfalfa
Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as w ...
area treated for alfalfa weevil in the Northeastern United States
The Northeastern United States, also referred to as the Northeast, the East Coast, or the American Northeast, is a geographic region of the United States. It is located on the Atlantic coast of North America, with Canada to its north, the Southe ...
remained 75 percent down.
Alligator weed
''Alternanthera philoxeroides'', commonly referred to as alligator weed, is a native species to the temperate regions of South America, which includes Argentina, Brazil, Paraguay and Uruguay. Argentina alone hosts around 27 species that fall with ...
was introduced to the United States from South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
. It takes root in shallow water, interfering with navigation
Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
, irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
, and flood control
Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...
. The alligator weed flea beetle and two other biological controls were released in Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
, greatly reducing the amount of land covered by the plant. Another aquatic weed, the giant salvinia (''Salvinia molesta
''Salvinia molesta'', commonly known as giant salvinia, or as kariba weed after it infested a large portion of Lake Kariba between Zimbabwe and Zambia, is an aquatic fern, native to south-eastern Brazil. It is a free-floating plant that does n ...
'') is a serious pest, covering waterways, reducing water flow and harming native species. Control with the salvinia weevil (''Cyrtobagous salviniae
''Cyrtobagous salviniae'' is a species of Curculionidae, weevil known as the salvinia weevil. It is used as an agent of biological pest control against the noxious weed, noxious aquatic plant giant salvinia (''Salvinia molesta'').
The adult wee ...
'') and the salvinia stem-borer moth (''Samea multiplicalis
''Samea multiplicalis'', the salvinia stem-borer moth, is an aquatic moth commonly found in freshwater habitats from the southern United States to Argentina, as well as in Australia where it was introduced in 1981. Salvinia stem-borer moths lay t ...
)'' is effective in warm climates, and in Zimbabwe, a 99% control of the weed was obtained over a two-year period.
Small commercially reared parasitoidal wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
s,[ '']Trichogramma
''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (2010 ...
ostriniae'', provide limited and erratic control of the European corn borer
The European corn borer (''Ostrinia nubilalis''), also known as the European corn worm or European high-flyer, is a moth of the family Crambidae which includes other grass moths. It is a pest of grain, particularly maize (''Zea mays''). The in ...
(''Ostrinia nubilalis''), a serious pest. Careful formulations of the bacterium ''Bacillus thuringiensis
''Bacillus thuringiensis'' (or Bt) is a gram-positive, soil-dwelling bacterium, the most commonly used biological pesticide worldwide. ''B. thuringiensis'' also occurs naturally in the gut of caterpillars of various types of moths and butterflie ...
'' are more effective. The O. nubilalis integrated control releasing Tricogramma brassicae (egg parasitoiod) and later Bacillus thuringiensis subs. kurstaki (larvicidae effect) reduce pest damages as better than insecticide treatments
The population of '' Levuana iridescens'', the Levuana moth, a serious coconut pest in Fiji
Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists ...
, was brought under control by a classical biological control program in the 1920s.
Augmentation
Augmentation involves the supplemental release of natural enemies that occur in a particular area, boosting the naturally occurring populations there. In inoculative release, small numbers of the control agents are released at intervals to allow them to reproduce, in the hope of setting up longer-term control and thus keeping the pest down to a low level, constituting prevention rather than cure. In inundative release, in contrast, large numbers are released in the hope of rapidly reducing a damaging pest population, correcting a problem that has already arisen. Augmentation can be effective, but is not guaranteed to work, and depends on the precise details of the interactions between each pest and control agent.
An example of inoculative release occurs in the horticultural production of several crops in greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...
s. Periodic releases of the parasitoidal wasp, ''Encarsia formosa
''Encarsia formosa'' is a species of chalcidoid wasp and a well known parasitoid of greenhouse whitefly, one of the first to be used commercially for biological pest control, from the 1920s. They can use at least 15 species of whitefly as a hos ...
'', are used to control greenhouse whitefly
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Description and taxonomy
The A ...
,[ while the predatory mite '']Phytoseiulus persimilis
''Phytoseiulus'' is a genus of mites in the Phytoseiidae family. A predatory mite, this is the mite predator most frequently used to control two-spotted spider mites in greenhouses and outdoor crops grown in mild environments. This mite was acci ...
'' is used for control of the two-spotted spider mite.
The egg parasite ''Trichogramma
''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (2010 ...
'' is frequently released inundatively to control harmful moths. New way for inundative releases are now introduced i.e. use of drones. Egg parasitoids are able to find the eggs of the target host by means of several cues. Kairomones were found on moth scales. Similarly, ''Bacillus thuringiensis'' and other microbial insecticides are used in large enough quantities for a rapid effect. Recommended release rates for ''Trichogramma'' in vegetable or field crops range from 5,000 to 200,000 per acre (1 to 50 per square metre) per week according to the level of pest infestation. Similarly, nematodes
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broa ...
that kill insects (that are entomopathogenic) are released at rates of millions and even billions per acre for control of certain soil-dwelling insect pests.
Conservation
The conservation of existing natural enemies in an environment is the third method of biological pest control.
Natural enemies are already adapted to the habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
and to the target pest, and their conservation can be simple and cost-effective, as when nectar-producing crop plants are grown in the borders of rice fields. These provide nectar to support parasitoids and predators of planthopper pests and have been demonstrated to be so effective (reducing pest densities by 10- or even 100-fold) that farmers sprayed 70% less insecticides and enjoyed yields boosted by 5%. Predators of aphids were similarly found to be present in tussock grasses by field boundary hedges in England, but they spread too slowly to reach the centers of fields. Control was improved by planting a meter-wide strip of tussock grasses in field centers, enabling aphid predators to overwinter there.
Cropping systems can be modified to favor natural enemies, a practice sometimes referred to as habitat manipulation. Providing a suitable habitat, such as a shelterbelt
A windbreak (shelterbelt) is a planting usually made up of one or more rows of trees or shrubs planted in such a manner as to provide shelter from the wind and to protect soil from erosion. They are commonly planted in hedgerows around the edges ...
, hedgerow
A hedge or hedgerow is a line of closely spaced shrubs and sometimes trees, planted and trained to form a barrier or to mark the boundary of an area, such as between neighbouring properties. Hedges that are used to separate a road from adjoini ...
, or beetle bank
A beetle bank, in agriculture and horticulture, is a form of biological pest control. It is a strip, preferably raised, planted with grasses (bunch grasses) and/or perennial plants, within a crop field or a garden, that fosters and provides habita ...
where beneficial insects such as parasitoidal wasps can live and reproduce, can help ensure the survival of populations of natural enemies. Things as simple as leaving a layer of fallen leaves or mulch in place provides a suitable food source for worms and provides a shelter for insects, in turn being a food source for such beneficial mammals as hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introducti ...
s and shrew
Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different fa ...
s. Compost pile
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
s and stacks of wood can provide shelter for invertebrates and small mammals. Long grass and pond
A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...
s support amphibians. Not removing dead annuals and non-hardy plants in the autumn allow insects to make use of their hollow stems during winter. In California, prune trees are sometimes planted in grape vineyards to provide an improved overwintering habitat or refuge for a key grape pest parasitoid. The providing of artificial shelters in the form of wooden caskets, box
A box (plural: boxes) is a container used for the storage or transportation of its contents. Most boxes have flat, parallel, rectangular sides. Boxes can be very small (like a matchbox) or very large (like a shipping box for furniture), and can ...
es or flowerpot
A flowerpot, planter, planterette or plant pot, is a container in which flowers and other plants are cultivated and displayed. Historically, and still to a significant extent today, they are made from plain terracotta with no ceramic glaze, wi ...
s is also sometimes undertaken, particularly in gardens, to make a cropped area more attractive to natural enemies. For example, earwigs
Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folded ...
are natural predators that can be encouraged in gardens by hanging upside-down flowerpots filled with straw
Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a number ...
or wood wool
Wood wool, known primarily as excelsior in North America, is a product made of wood slivers cut from logs. It is mainly used in packaging, for cooling pads in home evaporative cooling systems known as swamp coolers, for erosion control mats, and ...
. Green lacewings
The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera can be grouped together with the Megaloptera and Raphidioptera in the ...
can be encouraged by using plastic bottles with an open bottom and a roll of cardboard inside. Birdhouses enable insectivorous birds to nest; the most useful birds can be attracted by choosing an opening just large enough for the desired species.
In cotton production, the replacement of broad-spectrum insecticides with selective control measures such as Bt cotton
Bt cotton is a genetically modified pest resistant plant cotton variety, which produces an insecticide to combat bollworm.
Description
Strains of the bacterium '' Bacillus thuringiensis'' produce over 200 different Bt toxins, each harmful to ...
can create a more favorable environment for natural enemies of cotton pests due to reduced insecticide exposure risk. Such predators or parasitoids
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 parasi ...
can control pests not affected by the Bt protein. Reduced prey quality and abundance associated with increased control from Bt cotton can also indirectly decrease natural enemy populations in some cases, but the percentage of pests eaten or parasitized in Bt and non-Bt cotton are often similar.
Biological control agents
Predators
Predators are mainly free-living species that directly consume a large number of prey
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
during their whole lifetime. Given that many major crop pests are insects, many of the predators used in biological control are insectivorous species. Lady beetles
Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...
, and in particular their larvae which are active between May and July in the northern hemisphere, are voracious predators of aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s, and also consume mites
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
, scale insect
Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...
s and small caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
s. The spotted lady beetle ('' Coleomegilla maculata'') is also able to feed on the eggs and larvae of the Colorado potato beetle
The Colorado potato beetle (''Leptinotarsa decemlineata''), also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, or the potato bug, is a major pest of potato crops. It is about long, with a bright yellow/o ...
(''Leptinotarsa decemlineata'').
The larvae of many hoverfly
Hover flies, also called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while ...
species principally feed upon aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s, one larva devouring up to 400 in its lifetime. Their effectiveness in commercial crops has not been studied.
The running crab spider ''Philodromus cespitum
''Philodromus cespitum'' is a species of running crab spider in the family '' Philodromidae.'' It is found in North America, Europe, North Africa, and parts of the Middle East and Asia. ''P. cespitum'' is a foliage-dweller, and is the most abunda ...
'' also prey heavily on aphids, and act as a biological control agent in European fruit orchards.
Several species of entomopathogenic nematode
Entomopathogenic nematodes (EPN) are a group of nematodes (thread worms), that cause death to insects. The term ''entomopathogenic'' has a Greek origin, with ''entomon'', meaning ''insect'', and ''pathogenic'', which means ''causing disease''. Th ...
are important predators of insect and other invertebrate pests. 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
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
where they recover from their stagnated state of development and release their bacterial
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
symbionts. The bacterial symbionts reproduce and release toxins, which then kill the host insect. ''Phasmarhabditis hermaphrodita
''Phasmarhabditis hermaphrodita'' is a Facultative parasite, facultative parasitic nematode that can kill slugs and snails.Genena, M. A., Mostafa, F. A., Fouly, A. H., & Yousef, A. A. (2011). First record for the slug parasitic nematode, Phasmarh ...
'' is a microscopic nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
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
''Moraxella osloensis'' is a Gram-negative oxidase-positive, aerobic bacterium within the family Moraxellaceae in the gamma subdivision of the purple bacteria.
''Moraxella osloensis'' is a mutualistic symbiont of the slug-parasitic nematode ' ...
''. 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. Entomopathogenic nematodes have a limited shelf life
Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a ...
because of their limited resistance to high temperature and dry conditions.[ The type of soil they are applied to may also limit their effectiveness.][
Species used to control spider mites include the predatory mites '']Phytoseiulus persimilis
''Phytoseiulus'' is a genus of mites in the Phytoseiidae family. A predatory mite, this is the mite predator most frequently used to control two-spotted spider mites in greenhouses and outdoor crops grown in mild environments. This mite was acci ...
'', '' Neoseilus californicus,''[ and '' Amblyseius cucumeris'', the predatory midge '']Feltiella acarisuga
''Feltiella acarisuga'' is a species of predatory gall midge
Cecidomyiidae is a family of flies known as gall midges or gall gnats. As the name implies, the larvae of most gall midges feed within plant tissue, creating abnormal plant growths ...
'', and a ladybird '' Stethorus punctillum''.[ The bug '']Orius insidiosus
''Orius insidiosus'', common name the insidious flower bug, is a species of minute pirate bug, a predatory insect in the order Hemiptera (the true bugs). They are considered beneficial, as they feed on small pest arthropods and their eggs. They ...
'' has been successfully used against the two-spotted spider mite
''Tetranychus urticae'' ( common names include red spider mite and two-spotted spider mite) is a species of plant-feeding mite generally considered to be a pest. It is the most widely known member of the family Tetranychidae or spider mites. ...
and the western flower thrips
The western flower thrips 'Frankliniella occidentalis'' (Pergande)is an invasive pest insect in agriculture. This species of thrips is native to the Southwestern United States but has spread to other continents, including Europe, Australia (wher ...
(''Frankliniella occidentalis'').
Predators including ''Cactoblastis cactorum'' (mentioned above) can also be used to destroy invasive plant species. As another example, the poison hemlock moth (''Agonopterix alstroemeriana)'' can be used to control poison hemlock
''Conium maculatum'', colloquially known as hemlock, poison hemlock or wild hemlock, is a highly poisonous biennial herbaceous flowering plant in the carrot family Apiaceae, native to Europe and North Africa. A hardy plant capable of living in ...
(''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.
For rodent pests, cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s are effective biological control when used in conjunction with reduction of "harborage"/hiding locations. While cats are effective at preventing rodent "population explosions", they are not effective for eliminating pre-existing severe infestations. Barn owls
The barn owl (''Tyto alba'') is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere except for the polar and desert regions, Asia north of the Himalay ...
are also sometimes used as biological rodent control. Although there are no quantitative studies of the effectiveness of barn owls for this purpose, they are known rodent predators that can be used in addition to or instead of cats; they can be encouraged into an area with nest boxes.
In Honduras, where the mosquito ''Aedes aegypti
''Aedes aegypti'', the yellow fever mosquito, is a mosquito that can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognized by black and white markings on its legs ...
'' was transmitting dengue fever
Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characterist ...
and other infectious diseases, biological control was attempted by a community action plan; copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s, baby turtle
Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
s, and juvenile tilapia
Tilapia ( ) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were "Tilapiini"), with the economically most ...
were added to the wells and tanks where the mosquito breeds and the mosquito larvae were eliminated.
Even amongst arthropods usually thought of as obligate predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s of animals (especially other arthropods), floral
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...
food sources (nectar
Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...
and to a lesser degree pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
) are often useful adjunct sources. It had been noticed in one study that adult ''Adalia bipunctata
''Adalia bipunctata'', the two-spot ladybird, two-spotted ladybug or two-spotted lady beetle, is a carnivorous beetle of the family Coccinellidae that is found throughout the holarctic region. It is very common in western and central Europe. I ...
'' (predator and common biocontrol of ''Ephestia kuehniella
The Mediterranean flour moth or mill moth (''Ephestia kuehniella'') is a moth of the family Pyralidae. It is a common pest of cereal grains, especially flour. This moth is found throughout the world, especially in countries with temperate climat ...
'') could survive on flowers but never completed its life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
*Life-cycle hypothesis, ...
, so a meta-analysis was done to find such an overall trend in previously published data, if it existed. In some cases floral resources are outright necessary. Overall, floral resources (and an imitation, i.e. sugar water) increase longevity
The word " longevity" is sometimes used as a synonym for "life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, whereas ''life expectancy'' is always d ...
and fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
, meaning even predatory population numbers can depend on non-prey food abundance. Thus biocontrol population maintenance - and success - may depend on nearby flowers.
Parasitoids
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
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s are wasps
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. T ...
or flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
, and many have a very narrow host range. The most important groups are the ichneumonid wasps, which mainly use caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
s as hosts; braconid wasps
The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...
, which attack caterpillars and a wide range of other insects including aphids; chalcidoid wasps, which parasitize eggs and larvae of many insect species; and tachinid flies
The Tachinidae are a large and variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in this family ...
, which parasitize a wide range of insects including caterpillars, 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 ...
adults and larvae, and true bugs
Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to aroun ...
. Parasitoids are most effective at reducing pest populations when their host organisms have limited refuges to hide from them.
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. 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. 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. Shipping conditions can be too hot, and even vibrations from planes or trucks can adversely affect parasitoids.[
'']Encarsia formosa
''Encarsia formosa'' is a species of chalcidoid wasp and a well known parasitoid of greenhouse whitefly, one of the first to be used commercially for biological pest control, from the 1920s. They can use at least 15 species of whitefly as a hos ...
'' is a small parasitoid wasp attacking whiteflies
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Description and taxonomy
The ...
, sap-feeding insects which can cause wilting and 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. ''Gonatocerus ashmeadi
''Gonatocerus ashmeadi'' is a species of fairyfly
The Mymaridae, commonly known as fairyflies or fairy wasps, are a family of chalcidoid wasps found in temperate and tropical regions throughout the world. The family contains around 100 gener ...
'' (Hymenoptera
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
: Mymaridae
The Mymaridae, commonly known as fairyflies or fairy wasps, are a family (biology), family of chalcid wasp, chalcidoid wasps found in temperate and tropical regions throughout the world. The family contains around 100 genera with 1400 species.
F ...
) has been introduced to control the glassy-winged sharpshooter
The glassy-winged sharpshooter (''Homalodisca vitripennis'', formerly known as ''H. coagulata'') is a large leafhopper (family Cicadellidae), similar to other species of sharpshooter.
Description
These sharpshooters are about in length. Thei ...
''Homalodisca vitripennis'' (Hemiptera: Cicadellidae) in French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
and has successfully controlled ~95% of the pest density.
The eastern spruce budworm is an example of a destructive insect in fir and spruce
A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...
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.
There are a number of recent studies pursuing sustainable methods for controlling urban cockroaches using parasitic wasps. 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
Pathogenic micro-organisms include bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
, and viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
. They kill or debilitate their host and are relatively host-specific. Various microbial
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
insect diseases occur naturally, but may also be used as biological pesticide
A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
They are obtained from organisms inclu ...
s. When naturally occurring, these outbreaks are density-dependent in that they generally only occur as insect populations become denser.
The use of pathogens against aquatic weeds 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 straightfoward to apply in the same way as other biocontrols. 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. ''Bacillus thuringiensis
''Bacillus thuringiensis'' (or Bt) is a gram-positive, soil-dwelling bacterium, the most commonly used biological pesticide worldwide. ''B. thuringiensis'' also occurs naturally in the gut of caterpillars of various types of moths and butterflie ...
'', 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
Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...
n (moth
Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
, butterfly
Butterflies are insects in the macrolepidopteran clade Rhopalocera from the Order (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
), Coleoptera
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 ...
n (beetle) and Diptera
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
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
''Brassica'' () is a genus of plants in the cabbage and mustard family (Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called ''cole cr ...
s and fruit tree
A fruit tree is a tree which bears fruit that is consumed or used by animals and humans — all trees that are flowering plants produce fruit, which are the ripened ovaries of flowers containing one or more seeds. In horticultural usage, ...
s. Gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s from ''B. thuringiensis'' have also been incorporated into transgenic crops
Genetically modified crops (GM crops) are plants used in agriculture, the DNA of which has been modified using genetic engineering methods. Plant genomes can be engineered by physical methods or by use of ''Agrobacterium'' for the delivery of ...
, making the plants express some of the bacterium's toxins, which are protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s. These confer resistance to insect pests and thus reduce the necessity for pesticide use. If pests develop resistance to the toxins in these crops, ''B. thuringiensis'' will become useless in organic farming also.[
The bacterium '']Paenibacillus popilliae
''Paenibacillus popilliae'' (formerly ''Bacillus popilliae'') is a soil-dwelling, Gram-positive bacteria, Gram-positive, Bacillus (shape), rod-shaped bacterium. It is responsible for a disease (commonly called milky spore) of the white grubs of ...
'' which causes milky spore disease has been found useful in the control of Japanese beetle
The Japanese beetle (''Popillia japonica'') is a species of scarab beetle. The adult measures in length and in width, has iridescent copper-colored elytra and a green thorax and head. It is not very destructive in Japan (where it is controlle ...
, killing the larvae. It is very specific to its host species and is harmless to vertebrates and other invertebrates.
''Bacillus
''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacilli ...
'' spp.,[p.94-5, II. Biocontrol Modes of Action] fluorescent Pseudomonad
''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to ...
s, and Streptomycetes are controls of various fungal pathogens.[p.94]
Fungi
Entomopathogenic fungi
An entomopathogenic fungus is a fungus that can kill or seriously disable insects.
Typical life cycle
These fungi usually attach to the external body surface of insects in the form of microscopic spores (usually asexual, mitosporic spores also ...
, which cause disease in insects, include at least 14 species that attack aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s. ''Beauveria bassiana
''Beauveria bassiana'' is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the entomopathogenic fungi. It is used as a biological ...
'' is mass-produced and used to manage a wide variety of insect pests including whiteflies
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Description and taxonomy
The ...
, thrips
Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
, aphids and weevils
Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and herbivorous. Approximately 97,000 species of weevils are known. They belong to several families, ...
. ''Lecanicillium
''Lecanicillium'' is a genus of fungi in the order Hypocreales and is described as anamorphic Cordycipitaceae; 21 species are currently described. Some of these entomopathogenic fungus species were previously widely known as ''Verticillium leca ...
'' spp. are deployed against white flies, thrips and aphids. ''Metarhizium
''Metarhizium'' is a genus of entomopathogenic fungi in the Clavicipitaceae family. With the advent of genetic profiling, placing these fungi in proper taxa has now become possible. Most turn out to be the asexual forms (anamorphs) of fungi in ...
'' spp. are used against pests including beetles, locusts
Locusts (derived from the Vulgar Latin ''locusta'', meaning grasshopper) are various species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumst ...
and other grasshoppers, Hemiptera
Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...
, and spider mite
Spider mites are members of the Tetranychidae family, which includes about 1,200 species. They are part of the subclass Acari (mites). Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs, a ...
s. '' Paecilomyces fumosoroseus'' is effective against white flies, thrips and aphids; ''Purpureocillium
''Purpureocillium'' is a fungal genus in the Ophiocordycipitaceae family. The genus now contains at least 5 species with the type species ''Purpureocillium lilacinum'', a common saprobic, filamentous fungus. It has been isolated from a wide range ...
lilacinus'' is used against root-knot nematodes
Root-knot nematodes are plant-parasitic nematodes from the genus ''Meloidogyne''. They exist in soil in areas with hot climates or short winters. About 2000 plants worldwide are susceptible to infection by root-knot nematodes and they cause appro ...
, and 89 ''Trichoderma
''Trichoderma'' is a genus of fungi in the family Hypocreaceae that is present in all soils, where they are the most prevalent culturable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts. This ref ...
'' species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
against certain plant pathogens.[p.93] ''Trichoderma viride
''Trichoderma viride'' is a fungus and a biofungicide.
It is used for seed- and soil treatment for suppression of various diseases caused by fungal pathogens.
Biology
''T. viride'' is a mold which produces spores asexually, by mitosis. It ...
'' has been used against Dutch elm disease
Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into Americas, America ...
, and has shown some effect in suppressing silver leaf, a disease of stone fruits caused by the pathogenic fungus ''Chondrostereum purpureum
Silver leaf is a fungal disease of trees caused by the fungus plant pathogen ''Chondrostereum purpureum''. It attacks most species of the rose family Rosaceae, particularly the genus ''Prunus''. The disease is progressive and often fatal. The comm ...
''.
Pathogenic fungi may be controlled by other fungi, or bacteria or yeasts, such as: ''Gliocladium
''Gliocladium''Corda (1840) ''Icon. fung. (Prague)'' 4: 30. is an asexual fungal genus in the Hypocreaceae. Certain other species including ''Gliocladium virens'' were recently transferred to the genus ''Trichoderma'' and ''G. roseum'' became '' ...
'' spp., mycoparasitic ''Pythium
''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...
'' spp., binucleate
Binucleated cells are cells that contain two nuclei. This type of cell is most commonly found in cancer cells and may arise from a variety of causes. Binucleation can be easily visualized through staining and microscopy. In general, binucleati ...
types of ''Rhizoctonia
''Rhizoctonia'' is a genus of fungi in the order Cantharellales. Species form thin, effused, corticioid basidiocarps (fruit bodies), but are most frequently found in their sterile, anamorphic state. ''Rhizoctonia'' species are saprotrophic, but ...
'' spp., and ''Laetisaria
''Laetisaria'' is a genus of fungi in the family Corticiaceae. Basidiocarps (fruit bodies) are effused, corticioid, smooth, and grow as plant pathogens on grasses or agave leaves, or as lichenicolous fungi on lichens, or on dead wood. '' Laetis ...
'' spp.
The fungi ''Cordyceps
''Cordyceps'' is a genus of ascomycete fungi (sac fungi) that includes about 600 species. Most ''Cordyceps'' species are endoparasitoids, parasitic mainly on insects and other arthropods (they are thus entomopathogenic fungi); a few are parasiti ...
'' and ''Metacordyceps
''Metacordyceps'' is a genus of fungi in the family Clavicipitaceae. The anamorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleom ...
'' are deployed against a wide spectrum of arthropods. '' Entomophaga'' is effective against pests such as the green peach aphid.
Several members of Chytridiomycota
Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zoöspores. Chytrids ...
and Blastocladiomycota
Blastocladiomycota is one of the currently recognized phyla within the kingdom Fungi.Hibbett DS et al. 2007. A higher-level phylogenetic classification of the fungi. Mycological Research 111:509–47. Blastocladiomycota was originally the order ...
have been explored as agents of biological control. From Chytridiomycota, '' Synchytrium solstitiale'' is being considered as a control agent of the yellow star thistle
''Centaurea solstitialis'', the yellow star-thistle, is a species of thorny plant in the genus ''Centaurea'', which is part of the family Asteraceae. A winter annual, it is native to the Mediterranean Basin region and invasive in many other ...
(''Centaurea solstitialis'') in the United States.
Viruses
Baculoviruses are specific to individual insect host species and have been shown to be useful in biological pest control. For example, the Lymantria dispar multicapsid nuclear polyhedrosis virus
Lymantria dispar multicapsid nuclear polyhedrosis virus or LdMNPV is a viral infection in spongy moths (''Lymantria dispar'') that causes infected larvae to die and disintegrate. Infected larvae climb to the top of a tree and die. The larvae the ...
has been used to spray large areas of forest in North America where larvae of the spongy moth
''Lymantria dispar'', also known as the gypsy moth or the spongy moth, is a species of moth in the family Erebidae. ''Lymantria dispar'' is subdivided into several subspecies, with subspecies such as ''L. d. dispar'' and ''L. d. japonica'' bei ...
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.
A mammalian virus, the rabbit haemorrhagic disease virus
Rabbit hemorrhagic disease (RHD), also known as viral hemorrhagic disease (VHD), is a highly infectious and lethal form of viral hepatitis that affects European rabbits. Some viral strains also affect hares and cottontail rabbits. Mortality rate ...
was introduced to Australia to attempt to control the European rabbit
The European rabbit (''Oryctolagus cuniculus'') or coney is a species of rabbit native to the Iberian Peninsula (including Spain, Portugal, and southwestern France), western France, and the northern Atlas Mountains in northwest Africa. It has ...
populations there. 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. 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.
RNA mycovirus
Mycoviruses (Ancient Greek: μύκης ' ("fungus") + Latin '), also known as mycophages, are viruses that infect fungi. The majority of mycoviruses have double-stranded RNA (dsRNA) genomes and isometric particles, but approximately 30% have po ...
es are controls of various fungal pathogens.
Oomycota
''Lagenidium
''Lagenidium'' is a genus of Oomycota
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexu ...
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.
Competitors
The legume
A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...
vine ''Mucuna pruriens
''Mucuna pruriens'' is a tropical legume native to Africa and tropical Asia and widely naturalized and cultivated. Its English common names include monkey tamarind, velvet bean, Bengal velvet bean, Florida velvet bean, Mauritius velvet bean, Yo ...
'' is used in the countries of Benin
Benin ( , ; french: Bénin , ff, Benen), officially the Republic of Benin (french: République du Bénin), and formerly Dahomey, is a country in West Africa. It is bordered by Togo to the west, Nigeria to the east, Burkina Faso to the north ...
and Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
as a biological control for problematic ''Imperata cylindrica
''Imperata cylindrica'' (commonly known as cogongrass or kunai grass ) is a species of Perennial plant, perennial rhizomatous grass native to tropical and subtropical Asia, Micronesia, Melanesia, Australia, Africa, and southern Europe. It has al ...
'' grass: the vine is extremely vigorous and suppresses neighbouring plants by out-competing them for space and light. ''Mucuna pruriens'' is said not to be invasive outside its cultivated area. ''Desmodium
''Desmodium'' is a genus of plants in the legume family Fabaceae, sometimes called tick-trefoil, tick clover, hitch hikers or beggar lice. There are dozens of species and the delimitation of the genus has shifted much over time.
These are mostly ...
uncinatum'' can be used in push-pull farming to stop the parasitic plant
A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...
, witchweed (''Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
'').
The Australian bush fly, ''Musca vetustissima
''Musca vetustissima'', commonly known as the Australian bush fly, is a species of fly found in Australia. It is the specific fly that has given rise to the expression " Aussie salute".
Description
The Australian bush fly is a dung fly that ...
'', 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
George Francis Bornemissza (born György Ferenc Bornemissza; 11 February 1924 – 10 April 2014) was a Hungarian-born entomologist and ecologist. He studied science at the University of Budapest before obtaining his Ph.D. in zoology at the Un ...
of the Commonwealth Scientific and Industrial Research Organisation
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research.
CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...
, released forty-nine species of dung beetle
Dung beetles are beetles that feed on feces. Some species of dung beetles can bury dung 250 times their own mass in one night.
Many dung beetles, known as ''rollers'', roll dung into round balls, which are used as a food source or breeding cha ...
, to reduce the amount of dung and therefore also the potential breeding sites of the fly.
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
The emerald ash borer (''Agrilus planipennis''), also known by the acronym EAB, is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash species. Females lay eggs in bark crevices on ash trees, and larvae feed undern ...
, '' Agrilus planipennis'', an invasive 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 ...
from 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 ...
, which has destroyed tens of millions of ash trees
''Fraxinus'' (), commonly called ash, is a genus of flowering plants in the olive and lilac family, Oleaceae. It contains 45–65 species of usually medium to large trees, mostly deciduous, though a number of subtropical species are e ...
in its introduced range in 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 ...
. 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
''Oobius agrili'' is a parasitic non-stinging wasp of family Encyrtidae which is native to North Asia. It is a parasitoid of the emerald ash borer ('' Agrilus planipennis'' Fairmaire, family Buprestidae), an invasive species which has destroye ...
'', a solitary, parthenogenic egg parasitoid, and ''Spathius agrili
''Spathius agrili'' is a parasitic non-stinging wasp of family Braconidae which is native to North Asia. It is a parasitoid of the emerald ash borer (''Agrilus planipennis'' Fairmaire), an invasive species which has destroyed tens of millions of ...
'', a gregarious larval ectoparasitoid. These have been introduced and released into the United States of America
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
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
''Beauveria bassiana'' is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the entomopathogenic fungi. It is used as a biological ...
'', a fungal pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
with known insecticidal properties.
Target pests
Fungal pests
''Botrytis cinerea
''Botrytis cinerea'' is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" or ...
'' on lettuce
Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, ...
, by ''Fusarium
''Fusarium'' is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil mi ...
'' spp. and ''Penicillium claviforme
''Penicillium claviforme'' is a species of ''Penicillium'' within the phylum Ascomycota.
*It is found within the subgenus ''Terverticillium''.
*It has a coremium-type morphology in the sexual structures, named for its resemblance to matchstick ...
'', on grape
A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters.
The cultivation of grapes began perhaps 8,000 years ago, ...
and strawberry
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...
by ''Trichoderma
''Trichoderma'' is a genus of fungi in the family Hypocreaceae that is present in all soils, where they are the most prevalent culturable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts. This ref ...
'' spp., on strawberry by ''Cladosporium herbarum
''Cladosporium herbarum'' is a common fungus found worldwide in organic and inorganic matter. It is efficiently distributed in the air, where it exists as the most frequently occurring fungal species. It can grow over a wide range of temperature ...
'', on Chinese cabbage
Chinese cabbage (''Brassica rapa'', subspecies ''pekinensis'' and ''chinensis'') can refer to two cultivar groups of leaf vegetables often used in Chinese cuisine: the Pekinensis Group (napa cabbage) and the Chinensis Group (bok choy).
These ...
by ''Bacillus brevis
''Brevibacillus brevis'' (formerly known as ''Bacillus brevis'') is a Gram-positive, aerobic, motile, spore-forming, rod-shaped bacterium commonly found in soil, air, water, and decaying matter. It is rarely associated with infectious diseases. ...
'', and on various other crops by various yeasts and bacteria. ''Sclerotinia sclerotiorum
''Sclerotinia sclerotiorum'' is a plant pathogenic fungus and can cause a disease called white mold if conditions are conducive. ''S. sclerotiorum'' can also be known as cottony rot, watery soft rot, stem rot, drop, crown rot and blossom blight. ...
'' by several fungal biocontrols. Fungal pod infection of snap bean
Green beans are young, unripe fruits of various cultivars of the common bean (''Phaseolus vulgaris''), although immature or young pods of the runner bean (''Phaseolus coccineus''), yardlong bean ( ''Vigna unguiculata'' subsp. ''sesquipedalis' ...
by ''Trichoderma hamatum
''Trichoderma hamatum''Bainier (1906) In: ''Bull. Soc. mycol. Fr.'' 22:131 is a species of fungus in the family Hypocreaceae. It has been used a biological control
Biological control or biocontrol is a method of controlling pests, such as ...
'' if before or concurrent with infection.[p.93-4] ''Cryphonectria parasitica
The pathogenic fungus ''Cryphonectria parasitica'' (formerly ''Endothia parasitica'') is a member of the Ascomycota (sac fungi). This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America ...
'', ''Gaeumannomyces graminis
''Gaeumannomyces graminis'' var. ''graminis'' is a plant pathogen. This fungal pathogen produces extensive damage on the sheath of rice, causing black spots which protrude from the infected. This pathogen also generates a discoloration in the fol ...
'', ''Sclerotinia
''Sclerotinia'' is a genus of fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are ...
'' spp., and ''Ophiostoma novo-ulmi
''Ophiostoma'' is a genus of fungi within the family Ophiostomataceae. It was circumscribed in 1919 by mycologists Hans Sydow and Paul Sydow.
Species
*''Ophiostoma adjuncti''
*'' Ophiostoma ainoae''
*'' Ophiostoma allantosporum''
*'' Ophiosto ...
'' by viruses. Various powdery mildew
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as ...
s and rust
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...
s by various ''Bacillus
''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacilli ...
'' spp. and fluorescent Pseudomonad
''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to ...
s. ''Colletotrichum orbiculare
''Colletotrichum orbiculare'' is a plant pathogen of melons and cucumber. It causes the disease anthracnose that can effect Cucurbitaceae, curcubits causing lesions on various parts of the plant. It can effect cucumbers, melon, squash (plant), sq ...
'' will suppress further infection by itself if manipulated to produce plant-induced systemic resistance
Induced Systemic Resistance (ISR) is a resistance mechanism in plants that is activated by infection. Its mode of action does not depend on direct killing or inhibition of the invading pathogen, but rather on increasing physical or chemical barrie ...
by infected the lowest leaf.[p.95-6]
Difficulties
Many of the most important pests are exotic, invasive species that severely impact agriculture, horticulture, forestry, and urban environments. They tend to arrive without their co-evolved
parasites, pathogens and predators, and by escaping from these, populations may soar. Importing the natural enemies of these pests may seem a logical move but this may have unintended consequences
In the social sciences, unintended consequences (sometimes unanticipated consequences or unforeseen consequences) are outcomes of a purposeful action that are not intended or foreseen. The term was popularised in the twentieth century by Ameri ...
; regulations may be ineffective and there may be unanticipated effects on biodiversity, and the adoption of the techniques may prove challenging because of a lack of knowledge among farmers and growers.
Side effects
Biological control can affect biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
[ through predation, parasitism, pathogenicity, competition, or other attacks on non-target species.] An introduced control does not always target only the intended pest species; it can also target native species. In Hawaii during the 1940s parasitic wasps were introduced to control a lepidopteran pest and the wasps are still found there today. This may have a negative impact on the native ecosystem; however, host range and impacts need to be studied before declaring their impact on the environment.
Vertebrate animals tend to be generalist feeders, and seldom make good biological control agents; many of the classic cases of "biocontrol gone awry" involve vertebrates. For example, the cane toad
The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...
(''Rhinella marina'') was intentionally introduced to 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 ...
to control the greyback cane beetle (''Dermolepida albohirtum''), and other pests of sugar cane. 102 toads were obtained from Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
and bred in captivity to increase their numbers until they were released into the sugar cane fields of the tropic north in 1935. It was later discovered that the toads could not jump very high and so were unable to eat the cane beetles which stayed on the upper stalks of the cane plants. However, the toad thrived by feeding on other insects and soon spread very rapidly; it took over native amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
and brought foreign disease to native toad
Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands.
A distinction between frogs and toads is not made in scientif ...
s and frog
A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s, dramatically reducing their populations. Also, when it is threatened or handled, the cane toad releases poison
Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...
from parotoid gland
The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of toads and some frogs and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known collectiv ...
s on its shoulders; native Australian species such as goanna
A goanna is any one of several species of lizards of the genus '' Varanus'' found in Australia and Southeast Asia.
Around 70 species of ''Varanus'' are known, 25 of which are found in Australia. This varied group of carnivorous reptiles ranges ...
s, tiger snakes, dingo
The dingo (''Canis familiaris'', ''Canis familiaris dingo'', ''Canis dingo'', or ''Canis lupus dingo'') is an ancient (Basal (phylogenetics), basal) lineage of dog found in Australia (continent), Australia. Its taxonomic classification is de ...
s and northern quoll
The northern quoll (''Dasyurus hallucatus''), also known as the northern native cat, the North Australian native cat or the satanellus is a carnivorous marsupial native to Australia.
Taxonomy
The northern quoll is a member of the family Das ...
s that attempted to eat the toad were harmed or killed. However, there has been some recent evidence that native predators are adapting, both physiologically and through changing their behaviour, so in the long run, their populations may recover.
''Rhinocyllus conicus
''Rhinocyllus conicus'' is a species of true weevil. It is best known as a controversial agent of biological pest control which has been used against noxious thistles in the genera ''Carduus'', ''Cirsium'', ''Onopordum'', and ''Silybum''.
The a ...
'', a seed-feeding weevil, was introduced to North America to control exotic musk thistle
''Carduus nutans'', with the common names musk thistle, nodding thistle, and nodding plumeless thistle, is a biennial plant in the daisy and sunflower family Asteraceae. It is native to regions of Eurasia.
Description
''Carduus nutans'' is usua ...
(''Carduus nutans'') and Canadian thistle (''Cirsium arvense''). However, the weevil also attacks native thistles, harming such species as the endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
Platte thistle (''Cirsium neomexicanum'') by selecting larger plants (which reduced the gene pool), reducing seed production and ultimately threatening the species' survival. Similarly, the weevil ''Larinus planus
''Larinus planus'' is an insect of the Curculionidae ("true" weevil) family. They are oval shaped, dark brown or black, and about long. While native to Europe, it is also common in North America. It feeds on floral buds, primarily of thistles, ...
'' was also used to try to control the Canadian thistle, but it damaged other thistles as well. This included one species classified as threatened.
The small Asian mongoose Small Asian mongoose is a common name applied to two mammals which were formerly considered to be a single species:
* Javan mongoose
*Small Indian mongoose
The small Indian mongoose (''Urva auropunctata'') is a mongoose species native to Iraq an ...
(''Herpestus javanicus'') was introduced to Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
in order to control the rat population. However, the mongoose was diurnal, and the rats emerged at night; the mongoose, therefore, preyed on the endemic birds of Hawaii
There are 71 known taxa of birds endemic to the Hawaiian Islands, of which 30 are extinct, 6 possibly extinct and 30 of the remaining 48 species and subspecies are listed as endangered or threatened by the United States Fish and Wildlife Service. ...
, especially their egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s, more often than it ate the rats, and now both rats and mongooses threaten the birds. This introduction was undertaken without understanding the consequences of such an action. No regulations existed at the time, and more careful evaluation should prevent such releases now.
The sturdy and prolific eastern mosquitofish
The eastern mosquitofish (''Gambusia holbrooki'') is a species of freshwater fish, closely related to the western mosquitofish, ''Gambusia affinis''. It is a member of the family Poeciliidae of order Cyprinodontiformes. The eastern mosquitofish ...
(''Gambusia holbrooki'') is a native of the southeastern United States and was introduced around the world in the 1930s and '40s to feed on mosquito larvae and thus combat malaria
Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
. However, it has thrived at the expense of local species, causing a decline of endemic fish and frogs through competition for food resources, as well as through eating their eggs and larvae. In Australia, control of the mosquitofish is the subject of discussion; in 1989 researchers A. H. Arthington and L. L. Lloyd stated that "biological population control is well beyond present capabilities".
Grower education
A potential obstacle to the adoption of biological pest control measures is that growers may prefer to stay with the familiar use of pesticides. However, pesticides have undesired effects, including the development of resistance among pests, and the destruction of natural enemies; these may in turn enable outbreaks of pests of other species than the ones originally targeted, and on crops at a distance from those treated with pesticides. One method of increasing grower adoption of biocontrol methods involves letting them learn by doing, for example showing them simple field experiments, enabling them to observe the live predation of pests, or demonstrations of parasitised pests. In the Philippines, early-season sprays against leaf folder caterpillars were common practice, but growers were asked to follow a 'rule of thumb' of not spraying against leaf folders for the first 30 days after transplanting; participation in this resulted in a reduction of insecticide use by 1/3 and a change in grower perception of insecticide use.
Related techniques
Related to biological pest control is the technique of introducing sterile individuals into the native population of some organism. This technique is widely practised with insects
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...
: a large number of males sterilized by radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
are released into the environment, which proceed to compete
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
with the native males for females. Those females that copulate with the sterile males will lay infertile eggs, resulting in a decrease in the size of the population. Over time, with repeated introductions of sterile males, this could result in a significant decrease in the size of the organism's population. A similar technique has recently been applied to weeds using irradiated pollen, resulting in deformed seeds that do not sprout.
See also
* Beneficial insects
Beneficial insects (sometimes called beneficial bugs) are any of a number of species of insects that perform valued services like pollination and pest control. The concept of ''beneficial'' is subjective and only arises in light of desired outcome ...
* Biological control of gorse in New Zealand
* Chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked Glucosamine, D-glucosamine (deacetylated unit) and N-Acetylglucosamine, ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shell ...
* Companion planting
Companion planting in gardening and agriculture is the planting of different crops in proximity for any of a number of different reasons, including pest control, pollination, providing habitat for beneficial insects, maximizing use of space, and ...
* Insectary plants
Insectary plants are those that attract insects. As such, beneficial insectary plants are intentionally introduced into an ecosystem to increase pollen and nectar resources required by the natural enemies of the harmful or unwanted insects pest ( ...
* International Organization for Biological Control
The International Organization for Biological and Integrated Control (IOBC), is an organization, affiliated with the International Union of Biological Sciences (IUBS), organised to promote and study biological pest control, integrated pest manageme ...
* Inundative application
Inundative application of a biological control or natural enemy of a pest refers to the release of overwhelming numbers of a mass-produced biological control agent in the expectation of either achieving a rapid reduction of a pest (animal), pest ...
* Mating disruption
Mating disruption (MD) is a pest management technique designed to control certain insect pests by introducing artificial stimuli that confuse the individuals and disrupt mate localization and/or courtship, thus preventing mating and blocking the ...
* Nematophagous fungus
Nematophagous fungi are carnivorous fungi specialized in trapping and digesting nematodes. Around 160 species are known. There exist both species that live inside the nematodes from the beginning and others that catch them, mostly with glue tra ...
* Organic gardening
Organic horticulture is the science and art of growing fruits, vegetables, flowers, or ornamental plants by following the essential principles of organic agriculture in soil building and conservation, pest management, and heirloom variety preserva ...
* Organic farming
Organic farming, also known as ecological farming or biological farming,Labelling, article 30 o''Regulation (EU) 2018/848 of the European Parliament and of the Council of 30 May 2018 on organic production and labelling of organic products and re ...
* Permaculture#Zones, Permaculture zone 5
* Sustainable farming
* Sustainable gardening
* Zero Budget Farming
References
*
:*Chapter 6,
Further reading
General
* Wiedenmann, R. (2000)
Introduction to Biological Control
. Midwest Institute for Biological Control, Illinois.
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Effects on native biodiversity
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* Weeden, C. R.; Shelton, A. M.; Hoffman, M. P
* [https://web.archive.org/web/20071123044914/http://www.biotechnologyonline.gov.au/enviro/canetoad.cfm Cane toad: a case study]. 2003.
* Humphrey, J. and Hyatt. 2004. CSIRO Australian Animal Health Laboratory. ''Biological Control of the Cane Toad Bufo marinus in Australia''
*
* Johnson, M. 2000. Nature and Scope of Biological Control. ''Biological Control of Pests''.
Economic effects
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External links
Association of Natural Biocontrol Producers
International Organization for Biological Control
{{DEFAULTSORT:Biological Pest Control
Biological pest control,
American inventions
Chinese inventions
Insects in culture