Biological control of pests in
agricultureAgriculture is the production of food and goods through farming and forestry. Agriculture was the key development that led to the rise of human civilization, with the husbandry of domesticated animals and plants creating food surpluses that enabled the development of more densely populated and...
is a method of
controlling pestsPest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
(including
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
s,
miteMites, along with ticks, belong to the subclass Acarina and the class Arachnida. Mites are among the most diverse and successful of all the invertebrate groups. They have exploited an incredible array of habitats, and because of their small size most go totally unnoticed...
s,
weedA weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-made settings such as gardens, lawns or agricultural areas, but also in parks, woods and other natural areas. More specifically, the term is often...
s and
plant diseasesFor the journal, see Plant Pathology.Plant pathology is the scientific study of plant diseases caused by pathogens and environmental conditions...
) that relies on
predationIn ecology, predation describes a biological interaction where a predator feeds on its prey, . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of the prey...
,
parasitismParasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the host....
, herbivory, or other natural mechanisms. It can be an important component of
integrated pest managementIn agriculture, integrated pest management is a pest control strategy that uses a variety of complementary strategies including: mechanical devices, physical devices, genetic, biological, cultural management, and chemical management. These methods are done in three stages: prevention, observation,...
(IPM) programs.
Overview
Biological Control is defined as the reduction of pest
populationIn biology, a population is the collection of inter-breeding organisms of a particular species; in sociology, a collection of human beings. Individuals within a population share a factor may be reduced by statistical means, but such a generalization may be too vague to imply anything...
s by natural enemies and typically involves an active human role. Natural enemies of insect pests, also known as biological control agents, include predators,
parasitoidA parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism which it ultimately kills in the process. Thus they are similar to typical parasites except in the certain fate of the host. In a typical parasitic relationship, the...
s, and
pathogenA pathogen , infectious agent, or germ, is a biological agent that causes disease or illness to its host....
s. Biological control agents of plant
diseaseA disease or medical condition isan abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs...
s are most often referred to as antagonists. Biological control agents of weeds include
herbivoreA herbivore is an animal that is adapted to eat plants and not meat.Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants, algae and photosynthesizing bacteria....
s and plant pathogens. Predators, such as lady beetles and lacewings, are mainly free-living species that consume a large number of prey during their lifetime. Parasitoids are species whose immature stage develops on or within a single insect host, ultimately killing the host. Most have a very narrow host range. Many species of wasps and some flies are parasitoids. Pathogens are disease-causing organisms including
bacteriaThe bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, fungi, and viruses. They kill or debilitate their host and are relatively specific to certain insect groups. There are three basic types of biological control strategies; conservation, classical biological control, and augmentation.
Conservation
The conservation of natural enemies is probably the most important and readily available biological control practice available to homeowners and gardeners. Natural enemies occur in all areas, from the backyard garden to the commercial field. They are adapted to the local environment and to the target pest, and their conservation is generally simple and cost-effective. Lacewings, lady beetles, hover fly larvae, and parasitized
aphidAphids, also known as plant lice , are small plant-eating insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
mummies are almost always present in aphid colonies. Fungus-infected adult flies are often common following periods of high humidity. These naturally occurring biological controls are often susceptible to the same pesticides used to target their hosts. Preventing the accidental eradication of natural enemies is termed simple conservation.
Effects on native biodiversity
Biological control can potentially have positive and negative effects on
biodiversityBiodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems...
. Most of the time a biological control is introduced to an area to protect a native species from an invasive or exotic species that has moved into its area. The control is introduced to lessen the competition among native and invasive species. However, the introduced control does not always target only the intended species. It can also target native species.
When introducing a biological control to a new area, a primary concern is the host- or prey-specificity of the control agent. Generalist feeders (control agents that are not restricted to a single species or a small range of species) often make poor biological control agents, and may become invasive species themselves. For this reason, potential biological control agents should be subject to extensive testing and quarantine before release into any new environment. If a species is introduced and attacks a native species, the biodiversity in that area can change dramatically. When one native species is removed from an area, it may have filled an essential
nicheNiche may refer to:*Niche , an exedra or an apse that has been reduced in size;*Ecological niche, a term describing the relational position of an organism's species*Niche market, a focused, targetable portion of a market sector....
. When this
nicheNiche may refer to:*Niche , an exedra or an apse that has been reduced in size;*Ecological niche, a term describing the relational position of an organism's species*Niche market, a focused, targetable portion of a market sector....
is absent it may directly affect the entire
ecosystemAn ecosystem is a system of interdependent organisms which share the same habitat, in an area functioning together with all of the physical factors of the environment. Ecosystems can be permanent or temporary. Ecosystems usually form a number of food webs...
.
Because they tend to be generalist feeders, vertebrate animals seldom make good biological control agents, and many of the classic cases of "biocontrol gone awry" involve vertebrates. For example, the cane toad (
Bufo marinus) was introduced as a biological control and had significant negative impact on
biodiversityBiodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems...
. The cane toad was intentionally introduced to
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
to control the
cane beetleThe cane beetle, Dermolepida albohirtum, is a native Australian beetle and a pest of the sugar cane. Adult beetles eat the leaves of sugar cane but greater damage is the done by their larvae hatching underground and eating the roots, which either kills or stunts the growth of the plant.Larvae,...
. When introduced, the cane toad thrived very well and did not only feed on cane beetles but other insects as well. The cane toad soon spread very rapidly, thus taking over native
habitatThe term habitat has a number of meanings:* Habitat , a place where a species lives and grows** Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. The introduction of the cane toad also brought foreign disease to native
reptileReptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...
s. This drastically reduced the population of native toads and frogs. “The cane toad also exudes and can squirt
poisonIn the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism...
from the parotid glands on their shoulders when threatened or handled. This toxin contains a cocktail of chemicals that can kill animals that eat it. Freshwater
crocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
s,
goannaGoanna is the name used to refer to any number of Australian monitor lizards of the genus Varanus, as well as to certain species from Southeast Asia.There are around 30 species of goanna, 25 of which are found in Australia...
s, tiger snakes,
dingoThe Dingo is a domestic dog which has reverted to a wild state for thousands of years and today lives largely independent from humans in the majority of its distribution....
s and
northern quollThe Northern Quoll , also known as the Northern Native Cat, the Satanellus, the North Australian Native Cat or the Njanmak , is a carnivorous marsupial mammal, native to Australia.- Taxonomy :The Northern Quoll is a member of the family Dasyuridae, and is often stated to be the most distinctive...
s have all died after eating cane toads, as have pet dogs (Cane toad, 2003). This goes to show a small but deadly
organismIn biology, an organism is any living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole...
can alter the native
biodiversityBiodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems...
in an
ecosystemAn ecosystem is a system of interdependent organisms which share the same habitat, in an area functioning together with all of the physical factors of the environment. Ecosystems can be permanent or temporary. Ecosystems usually form a number of food webs...
in a very expedient manner. A
pyramidA pyramid is a building where the outer surfaces are triangular and converge at a point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least four faces...
effect can take place if native species are reduced or eradicated. The
domino effectThe domino effect is a chain reaction that occurs when a small change causes a similar change nearby, which then will cause another similar change, and so on in linear sequence. The term is best known as a mechanical effect, and is used as an analogy to a falling row of dominoes...
keeps on going and can potentially exude on other bordering ecosystems until an equilibrium is reached.
A second example of a biological control agent that subsequently crossed over to native species is the
Rhinocyllus conicusRhinocyllus 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 seed feeding weevil was introduced to North America to control exotic
thistleThistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant - on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...
s (Musk and Canadian). However, the weevil did not target only the exotic thistles, it also targeted native thistles that are essential to various native insects. The native insects rely solely on native thistles and do not adapt to other plant species. Therefore, they cannot survive. Biological controls do not always have negative impacts on biodiversity (Corry 2000).
Successful biological control reduces the
densityThe density of a material is defined as its mass per unit volume. The symbol of density is ρ .- Formula :Mathematically:where: is the density, is the mass, is the volume....
of the target species over several years, thus providing the potential for native species to re-establish. In addition, regeneration and reestablishment programs can aid to the recovery of native species. Native species can be affected in a positive way as well. To develop or find a biological control that exerts control only on the targeted species is a very lengthy process of
researchResearch can be defined to be search for knowledge or any systematic investigation to establish facts. The primary purpose for applied research is discovering, interpreting, and the development of methods and systems for the advancement of human knowledge on a wide variety of scientific matters of...
and
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s. In the late 1800’s, the
citrusCitrus is a common term and genus of flowering plants in the family Rutaceae, originating in tropical and subtropical southeast regions of the world. The most well known examples are the orange, the lemon, the grapefruit, and the lime. The Latin word citrus was borrowed from ancient Greek kedros...
industry was in great fear when the
cottony cushion scaleIcerya purchasi is a scale insect that feeds on several species of woody plants, most notably on Citrus and Pittosporum. Originally identified in 1878 as a New Zealand located consumer of Kangaroo Acacia, it is now found worldwide where citrus crops are grown.-Life cycle:This scale infests twigs...
was discovered. This organism could cause a great deal of economic loss to the industry. However, a biological control was introduced. The vedalia beetle and a
parasitoidA parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism which it ultimately kills in the process. Thus they are similar to typical parasites except in the certain fate of the host. In a typical parasitic relationship, the...
flyTrue flies are insects of the order Diptera , possessing a single pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax....
were introduced to control the pest. Within a few years time, the cottony cushion scale was controlled by the natural enemies and the citrus industry suffered little financial loss. Many exotic or invasive species can suppress the development of native species. The introduction of an effective biological control that reduces the population of the invasive species allows the rejuvenation of the native species. Biological controls can reduce competition for
bioticBiotic means relating to, produced by, or caused by living organisms.The term biotic may also refer to:*Life, or ecosystem, the condition of living organisms,*Biology, the study of life*Biotic component in ecology,...
and abiotic factors which can result in the re-establishment of the once over ran native species.
Effects on invasive species
Invasive species are closely associated with biological controls because the environment in which they are invasive most likely does not contain their natural enemies. If invasive species are not controlled, biodiversity may be at great threat in the affected area. An example of an invasive species is the
alligator weedAlternanthera philoxeroides, commonly known as Alligator weed, is an immersed aquatic plant. It originated in South America, but has spread to many parts of the world and is considered an invasive species in Australia, China, New Zealand, Thailand and the United States.Alligator weed can grow in a...
. This plant was introduced to the United States from
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
. This aquatic weed spreads very rapidly and causes many problems in lakes and rivers. The weed takes root in shallow water causing major problems such as
navigationNavigation is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. The word navigate is derived from the Latin "navigare", meaning "to sail"...
,
irrigationIrrigation is an artificial application of water to the soil. It is usually used to assist in growing crops in dry areas and during periods of inadequate rainfall...
, and
flood controlIn communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...
. The
alligator weed flea beetleAgasicles hygrophila is a species of leaf beetle known by the common name alligator weed flea beetle. It has been used successfully as an agent of biological pest control against the noxious aquatic plant known as alligator weed .This beetle is native to South America but has been imported to areas...
and two other biological controls were released in
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
. Because of their success, Florida banned the use of herbicides to control alligator weed three years after the controls were introduced (Cofrancesco 2007). Biological controls for invasive species also can have a negative impact on biodiversity.
The cane toad, as mentioned previously, is a great example of trying to control an invasive species. The cane toad was introduced to eradicate an invasive species. However, it became invasive, thus altering the biodiversity. The introduction of the cane toad could have potentially caused more of a disturbance in biodiversity than the targeted species did.
Effects on future
With further research and more scientific experiments, biological control could potentially play a huge role in the future of pest prevention. Biological control is being used among society today; however, it could someday reduce the use of many pesticides and herbicides. Since biological control could potentially have a large economic value, if found to be successful, research and job fields would increase continually. By increasing awareness of biological controls among more people, new successful biological controls could be discovered in the future. This could eliminate the overuse of chemicals. Biodiversity would increase, too, because of the reduction of chemical applications that often do affect not only the single species they are intended to kill, but other species as well.
Economic effects
Biological control is heavily analyzed by the amount of economic gain that directly comes from biological control. Many of the known economics of biological control are related directly to agriculture practices. Since agriculture has a huge impact on biodiversity this could potentially increase the biodiversity among agricultural practices. In order for agriculture to keep up with the growing population, many inputs are increased resulting in the loss of un-harmful species. Biological control use has been very minimal in agriculture. Less than 1% of global
pest controlPest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
sales of $30 billion involve biological methods (Griffiths 2007:in press).
Very few case studies on the cost-benefit analysis of biological control have been done however a few have taken place. A Critical evaluation of augmentative biological control has found four case studies. In one case, “the releases of a parasitoid
Gryon pennsylvanicum Ashmead to control the true bug
Anasa tristis on pumpkins produced lower net benefit (in dollars) than applications of esfenvalerate (pesticide); 18% lower in one year and 120% lower in the next. In 1 year of the study, a combination of augmentative releases and use of a resistant
pumpkinPumpkin is a gourd-like squash of the genus Cucurbita and the family Cucurbitaceae . It is a common name of or can refer to cultivars of any one of the species Cucurbita pepo, Cucurbita mixta, Cucurbita maxima, and Cucurbita moschata. They are typically orange or yellow and have many creases...
variety produced greater net benefit than pesticide alone, but not pesticide combined with the resistant variety (Olson et al. 1996)”.
Another case study found that releases of
T. nubilale were considerably less cost-effective than pesticide applications used to control ECB on feed corn and fresh-market sweet corn. Pesticide applications produced 87% and 45% more net benefit (in dollars) than augmentation for feed corn and fresh market corn, respectively. In seed corn, however,
Trichogramma releases produced essentially equivalent net benefits to pesticide treatments. In a third cost-benefit analysis of augmentation, Lundgren et al. (2002) showed that
Trichogramma brassicae Bezdenko releases produced considerably less net benefit (94%; measured in cabbage head production) than
methomylMethomyl is a carbamate insecticide. It was introduced in 1966, but its use is restricted because of its high toxicity to humans. Its current primary use is on alfalfa for forage....
treatments (Andow 1997).
In two other studies, “biological control releases were about two times the cost of pesticide applications; this was true for releases of a parasitoid,
Choetospila elegans Westwood, used to control a stored product pest,
Rhyzopertha dominica (F.) (Flinn et al.,1996) and releases of green lacewings,
Chrysoperla carnea Stephens to control leafhoppers in grapes (Daane et al., 1996). Finally Prokrym et al. (1992) suggested that
Trichogramma releases were about six times as expensive as pesticide treatments for
O. nubilalisThe European Corn Borer is a pest of grain, particularly maize. The insect is native to Europe originally infesting varieties of millet including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was probably introduced from Europe several...
in sweet corn,” (Collier 2003.
Another study shows that even though being possibly less effective, biological
pest controlPest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
still produces a benefit-to-cost ratio of 11:1. One study has estimated that a successful biocontrol program returns £32 in benefits for each £1 invested in developing and implementing the program, i.e. a 32:1 benefit-to-cost ratio. The same study had shown that an average chemical pesticide program only returned profits in the ratio of 13:1.
So while the exact numbers vary, the majority of these case studies shows that biological control is less cost effective than chemical applications and in result raises a flag that more research needs to be done. With progression in research, we can use more controls at a cheaper cost and increase the amount of biodiversity in areas because of the minimal use of chemicals that cannot target a specific species of pest.
Classical biological control
Classical biological control is the introduction of natural enemies to a new locale where they did not originate or do not occur naturally. This is usually done by government authorities. In many instances the complex of natural enemies associated with an insect pest may be inadequate. This is especially evident when an insect pest is accidentally introduced into a new geographic area without its associated natural enemies. These introduced pests are referred to as exotic pests and comprise about 40% of the insect pests in the United States. Examples of introduced vegetable pests include the
European corn borerThe European Corn Borer is a pest of grain, particularly maize. The insect is native to Europe originally infesting varieties of millet including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was probably introduced from Europe several...
(
Ostrinia nubilalis), one of the most destructive insects in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
. To obtain the needed natural enemies, scientists turned to classical biological control. This is the practice of importing, and releasing for establishment, natural enemies to control an introduced (exotic) pest, although it is also practiced against native insect pests. The first step in the process is to determine the origin of the introduced pest and then collect appropriate natural enemies associated with the pest or closely related species. The natural enemy is then passed through a rigorous
quarantineQuarantine is voluntary or compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease...
process, to ensure that no unwanted organisms (such as hyperparasitoids) are introduced, then they are mass produced, and released. Follow-up studies are conducted to determine if the natural enemy becomes successfully established at the site of release, and to assess the long-term benefit of its presence.
There are many examples of successful classical biological control programs. One of the earliest successes was in controlling
Icerya purchasiIcerya purchasi is a scale insect that feeds on several species of woody plants, most notably on Citrus and Pittosporum. Originally identified in 1878 as a New Zealand located consumer of Kangaroo Acacia, it is now found worldwide where citrus crops are grown.-Life cycle:This scale infests twigs...
, the cottony cushion scale, a pest that was devastating the
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
citrus industry in the late 1800s. A predatory insect
Rodolia cardinalisRodolia cardinalis is a species of ladybird beetle that is sometimes described as endemic to Australia.-New Zealand:...
(the Vedalia Beetle), and a parasitoid fly were introduced from Australia by
Charles Valentine RileyCharles Valentine Riley was an entomologist and artist.He was born in London on September 19, 1843 and moved to the United States at the age of 17...
. Within a few years the cottony cushion scale was completely controlled by these introduced natural enemies.
Damage from
Hypera postica Gyllenhal, the alfalfa weevil, a serious introduced pest of forage, was substantially reduced by the introduction of several natural enemies. About 20 years after their introduction, the population of
weevilA weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than 6 mm , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
s, in the
alfalfaAlfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop. In the UK, Australia, and New Zealand it is known as lucerne and as lucerne grass in south Asia...
area treated for alfalfa weevil in the
Northeastern United StatesThe Northeastern United States is a region of the United States. According to the definition used by the United States Census Bureau, the Northeast region consists of nine states: the New England states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island and Connecticut; and the...
, was reduced by 75 percent. A small
waspThe term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their numbers,...
,
Trichogramma ostriniae, was introduced from
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
to help control the
European corn borerThe European Corn Borer is a pest of grain, particularly maize. The insect is native to Europe originally infesting varieties of millet including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was probably introduced from Europe several...
making it a recent example of a long history of classical biological control efforts for this major pest. Many classical biological control programs for insect pests and weeds are under way across the United States and
CanadaCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
. The population of
Levuana irridescens (the Levuana moth), a serious coconut pest in
FijiFiji , officially the Republic of the Fiji Islands , is an island nation in the South Pacific Ocean east of Vanuatu, west of Tonga and south of Tuvalu. The country comprises an archipelago of about 322 islands, of which 106 are permanently inhabited, and 522 islets...
was brought under control by a classical biological control program in the 1920s.
Classical biological control is long lasting and inexpensive. Other than the initial costs of collection, importation, and rearing, little expense is incurred. When a natural enemy is successfully established it rarely requires additional input and it continues to kill the pest with no direct help from humans and at no cost. Unfortunately, classical biological control does not always work. It is usually most effective against exotic pests and less so against native insect pests. The reasons for failure are not often known, but may include the release of too few individuals, poor adaptation of the natural enemy to environmental conditions at the release location, and lack of synchrony between the
life cycleA life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
of the natural enemy and host pest.
Augmentation
This third type of biological control involves the supplemental release of natural enemies. Relatively few natural enemies may be released at a critical time of the season (inoculative release) or literally millions may be released (inundative release). Additionally, the cropping system may be modified to favor or augment the natural enemies. This latter practice is frequently referred to as habitat manipulation.
Bold textAn example of inoculative release occurs in greenhouse production of several crops. Periodic releases of the parasitoid,
Encarsia formosaEncarsia formosa is a species of wasp and a well known parasitoid of greenhouse whitefly. The tiny females are black with a yellow abdomen and opalescent wings. Males are extremely rare by comparison to females...
, are used to control greenhouse
whiteflyThe whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
, and the predaceous mite,
Phytoseiulus persimilis, is used for control of the two-spotted spider mite.
Lady beetles, lacewings, or parasitoids such as those from the genus
TrichogrammaThe wasps of genus Trichogramma are some of the most widely-studied agents of biological control in the field of entomology. Trichogramma wasps are tiny Hymenopteran insects, measuring 1 millimeter in length or less, that parasitize the eggs of many types of agricultural pest insects...
are frequently released in large numbers (inundative release). 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 depending on level of pest infestation. Similarly, entomopathogenic nematodes are released at rates of millions and even billions per acre for control of certain soil-dwelling insect pests.
The spraying of
octopamineOctopamine is a biogenic amine that is closely related to noradrenaline, and has noradrenergic and dopaminergic effects. Biosynthesis of the D enantiomer is by β-hydroxylation of tyramine by the enzyme dopamine β-hydroxylase...
analogues (such as 3-FMC) has been suggested as a way to boost the effectiveness of augmentation.
OctopamineOctopamine is a biogenic amine that is closely related to noradrenaline, and has noradrenergic and dopaminergic effects. Biosynthesis of the D enantiomer is by β-hydroxylation of tyramine by the enzyme dopamine β-hydroxylase...
, regarded as the
invertebrateAn invertebrate is an animal without a vertebral column. The group includes 95% of all animal species — all animals except those in the Chordate subphylum Vertebrata ....
counterpart of
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
plays a role in activating the insects' flight-or-fight response. The idea behind using octopamine analogues to augment biological control is that natural enemies will be more effective in their eradication of the pest, since the pest will be behaving in an unnatural way because its flight-or-fight mechanism has been activated. Octopamine analogues are purported to have two desirable characteristics for this type of application: (1) they affect insects at very low dosages (2) they do not have a physiological effect in humans (or other vertebrates).
Habitat or environmental manipulation is another form of augmentation. This tactic involves altering the cropping system to augment or enhance the effectiveness of a natural enemy. Many adult parasitoids and predators benefit from sources of nectar and the protection provided by refuges such as hedgerows, cover crops, and weedy borders. Also, the provisioning of natural shelters in the form of wooden caskets,
boxBox describes a variety of containers and receptacles for permanent use as storage, or for temporary use often for transporting contents....
es or (turnaround)
flowerpotA plantpot is any container in which plants are cultivated. Terra cotta is often used to make plantpots but they are also often made from plastic, wood, stone, or sometimes biodegradable material. An example of biodegradable pots are the so-called "Jiffy" pots...
s is a form of this. For example, the stimulation of the natural predator
Dermaptera is done in gardens by hanging up turnaround flowerpots with
strawStraw is an agricultural by-product, the dry stalk of a cereal plant, after the grain or seed has been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat...
or wood wool.
Mixed plantings and the provision of flowering borders can increase the diversity of habitats and provide shelter and alternative food sources. They are easily incorporated into home gardens and even small-scale commercial plantings, but are more difficult to accommodate in large-scale crop production. There may also be some conflict with pest control for the large producer because of the difficulty of targeting the pest species and the use of refuges by the pest insects as well as natural enemies.
Examples of habitat manipulation include growing flowering plants (pollen and nectar sources) such as
BuckwheatBuckwheat refers to plants in two genera of the dicot family Polygonaceae: the Eurasian genus Fagopyrum, and the North American genus Eriogonum. The crop plant, common buckwheat, is Fagopyrum esculentum. Tartary buckwheat or "bitter buckwheat" is also used as a crop, but it is much less common...
near crops to attract and maintain populations of natural enemies. For example, hover fly adults can be attracted to umbelliferous plants in bloom.
Biological control experts in California have demonstrated that planting prune trees in grape vineyards provides an improved overwintering habitat or refuge for a key grape pest parasitoid. The prune trees harbor an alternate host for the parasitoid, which could previously overwinter only at great distances from most vineyards. Caution should be used with this tactic because some plants attractive to natural enemies may also be hosts for certain plant diseases, especially plant viruses that could be vectored by insect pests to the crop. Although the tactic appears to hold much promise, only a few examples have been adequately researched and developed.
Examples of predators
Ladybugs, and in particular their larvae which are active between May and July in the northern hemisphere, are voracious predators of
aphidAphids, also known as plant lice , are small plant-eating insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s such as greenfly and
blackflyBlackfly, black-fly, or black fly may refer to:*Black fly, a fly of the family Simuliidae*Blackfly , a 2001 Canadian comedy series*Aphid or blackfly...
, and will also consume
mitesMITES, or Minority Introduction to Engineering and Science, is a six-week summer program for rising high school seniors held at the Massachusetts Institute of Technology. Its purpose is to expose students from minority, or otherwise disadvantaged backgrounds, to the fields of science and engineering...
,
scale insectThe scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects....
s and small
caterpillarCaterpillars are the larval form of a member of the order Lepidoptera . They are mostly phytophagous in food habit, with some species being entomophagous. Caterpillars are voracious feeders and many of them are considered pests in agriculture...
s. The ladybug is a very familiar beetle with various colored markings, whilst its larvae are initially small and spidery, growing up to 17 mm long. The larvae have a tapering segmented grey/black body with orange/yellow markings and ferocious mouthparts. They can be encouraged by cultivating a patch of
nettleNettle is the common name for between 30-45 species of flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though mainly temperate distribution...
s in the garden and by leaving hollow stems and some plant debris over winter so that they can hibernate.
HoverfliesFlies in the family Syrphidae are commonly known as hoverflies, flower flies, or syrphid flies.As their common names suggest, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae eat a wide range of foods...
resemble slightly darker
beeBees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s or
waspThe term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their numbers,...
s and they have characteristic hovering, darting flight patterns. There are over 100 species of hoverfly whose larvae principally feed upon greenfly, one larva devouring up to fifty a day, or 1000 in its lifetime. They also eat fruit tree
spider miteSpider mites are members of the Acari family Tetranychidae, which includes about 1600 species. They generally live on the under sides of leaves of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed...
s and small caterpillars. Adults feed on nectar and
pollenPollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement between the stamens to the pistil of flowering plants or from the male cone to the...
, which they require for egg production. Eggs are minute (1 mm), pale yellow white and laid singly near greenfly colonies. Larvae are 8–17 mm long, disguised to resemble bird droppings, they are legless and have no distinct head. Semi-transparent in a range of colours from green, white, brown and black.
Hoverflies can be encouraged by growing attractant flowers such as the
poached egg plantLimnanthes douglasii is a species of flowering plant in the meadowfoam family commonly known as poached egg plant and Douglas' meadowfoam. It is native to California and Oregon, where it grows in wet, grassy habitat, such as vernal pools and spring meadows. It can grow in poorly drained clay soils...
(Limnanthes douglasii),
marigoldMarigold may refer to:Plants:* Marigold , Tagetes* Pot marigold, Calendula* Mexican marigold, Tagetes erecta* Tree marigold, Tithonia diversifolia* Desert marigold, Baileya multiradiata...
s or
phaceliaPhacelia, the phacelias or scorpionweeds, is a large plant genus. It contains about 200 species of herbs, native of Western North America , Eastern USA and South America....
throughout the growing season.
DragonfliesA dragonfly is a type of insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera. It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
are important predators of mosquitoes, both in the water, where the dragonfly naiads eat
mosquitoMosquito is a common insect in the family Culicidae...
larvaA larva is a young form of animal with indirect development, going through or undergoing metamorphosis ....
e, and in the air, where adult dragonflies capture and eat adult mosquitoes. Community-wide mosquito control programs that spray adult mosquitoes also kill dragonflies, thus removing an important biocontrol agent, and can actually increase mosquito populations in the long term.
Other useful garden predators include
lacewingsGreen lacewings are insects in the large family Chrysopidae of the order Neuroptera. There about 85 genera and 1,300–2,000 species in this widespread group...
,
pirate bugsThe Anthocoridae are a family of bugs, commonly called minute pirate bugs or flower bugs.-Name:The vernacular name probably stems from the notion that these very small animals can do much pain to humans, just like small pirate vessels can do so to big ships.The scientific name is a combination of...
, rove and ground beetles, aphid midge,
centipedeCentipedes are arthropods belonging to the class Chilopoda and the Subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. A key trait uniting this group is a pair of venom claws or forcipules formed from a modified first appendage...
s, predatory mites, as well as larger fauna such as
frogFrogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by long hind legs, a short body, webbed digits , protruding eyes and the absence of a tail...
s,
toadA toad can refer to a number of species of amphibians in the order Anura. A distinction is often made between frogs and toads by their appearance, prompted by the convergent adaptation among so-called "toads" to dry habitats. Many "toads" have leathery skin for better water retention, and brown...
s,
lizardLizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s,
hedgehogA hedgehog is any of the spiny mammals of the subfamily Erinaceinae and the order Erinaceomorpha. There are 17 species of hedgehog in five genera, found through parts of Europe, Asia, Africa, and New Zealand. There are no hedgehogs native to Australia, and no living species native to North America;...
s,
slow-worms and birds. Cats and rat terriers kill field mice, rats, June bugs, and birds. Dogs chase away many types of pest animals.
DachshundThe dachshund is a short-legged, elongated dog breed, of the hound family. The standard size was developed to scent, chase, and flush badgers and other burrow-dwelling animals, while the miniature was developed to hunt smaller prey, like rabbits....
s are bred specifically to fit inside tunnels underground to kill badgers.
- Phytoseiulus persimilis (against spider mites)
- Amblyseius californicus (against spider mites)
- Amblyseius cucumeris (against spider mites)
- Typhlodromips swirskii (against spider mites, thrips, and white flies)
- Feltiella acarisuga
Feltiella acarisuga is a predatory gall midge which will feed on various species of spider mites. It is especially common when spider mites occur in colonies. It requires a high spider mite density and high humidities to become established....
(against spider mites)
- Stethorus punctillum (against spider mites)
- Macrolophus caluginosus (against spider mites)
- Encarsia formosa
Encarsia formosa is a species of wasp and a well known parasitoid of greenhouse whitefly. The tiny females are black with a yellow abdomen and opalescent wings. Males are extremely rare by comparison to females...
(against white flies)
- Eretmocerus spp. (against white flies)
Parasitoid insects
Most insect parasitoids are wasps or flies. Parasitiods comprise a diverse range of insects that lay their egg on or in the body of an insect host, which is then used as a food for developing larvae. Parasitic
waspThe term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their numbers,...
s take much longer than predators to consume their victims, for if the larvae were to eat too fast they would run out of food before they became adults. Such parasites are very useful in the organic garden, for they are very efficient hunters, always at work searching for pest invaders. As adults they require high energy fuel as they fly from place to place, and feed upon nectar, pollen and sap, thereby pollinating plenty of flowering plants, particularly
buckwheatBuckwheat refers to plants in two genera of the dicot family Polygonaceae: the Eurasian genus Fagopyrum, and the North American genus Eriogonum. The crop plant, common buckwheat, is Fagopyrum esculentum. Tartary buckwheat or "bitter buckwheat" is also used as a crop, but it is much less common...
, umbellifers, and
compositesThe family Asteraceae or Compositae is the second largest family of flowering plants, in terms of number of species....
will encourage their presence.
Four of the most important groups are:
- Ichneumonid wasps
The Ichneumonoidea are insects classified in the hymenopteran suborder Apocrita. The superfamily is made up of the ichneumon wasps and the braconids...
: (5–10 mm). Prey mainly on caterpillarCaterpillars are the larval form of a member of the order Lepidoptera . They are mostly phytophagous in food habit, with some species being entomophagous. Caterpillars are voracious feeders and many of them are considered pests in agriculture...
s of butterflies and mothsMoths may refer to:* Gustav Moths , German rower* Moths , Lower Definition's first full-length album* The Moths!, an English indie rock band* MOTHS, members of the Memorable Order of Tin Hats...
.
- Braconid wasps: Tiny wasps (up to 5 mm) attack caterpillars and a wide range of other insects including greenfly. A common parasite of the cabbage white caterpillar- seen as clusters of sulphur yellow cocoons bursting from collapsed caterpillar skin.
- Chalcid wasp
Chalcid wasps belong to the insect order Hymenoptera, and are one of the largest groups within the order, with some 22,000 known species, and an estimated total diversity of anywhere from 60,000 to more than 500,000 species, meaning the vast majority have yet to be discovered and described.Most of...
s: Among the smallest of insects (<3 mm). Parasitize eggs/larvae of greenfly, whiteflyThe whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
, cabbage caterpillars, scale insectThe scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects....
s and Strawberry Tortrix Moth (Acleris comarianaThe Strawberry Tortrix is a moth of the Tortricidae family. It is found in Europe, the Caucasus, Amur, Kamchatka, China, Korea and Japan.The wingspan is 13-18 mm....
).
- Tachinid flies
Tachinidae is a large and rather variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. There are over 1300 species in North America. Insects in this family are commonly called tachina flies or simply tachinids.They occur in...
: Parasitize a wide range of insects including caterpillars, adult and larval beetleBeetles are the group of insects with the largest number of known species. They are classified in the order Coleoptera , which contains more described species than in any other order in the animal kingdom, constituting about 25% of all known life-forms...
s, true bugs, and others.
Biological control with micro-organisms
Various microbial insect diseases occur naturally, but may also be used as
biological pesticideThe term biopesticide is used for microbial biological pest control agents that are applied in a similar manner to chemical pesticides. Commonly these are bacterial, but there are also examples of fungal control agents, including Trichoderma spp. and Ampelomyces quisqualis . Bacillus subtilis...
s. When naturally occurring, these outbreaks are density dependent in that they generally only occur as insect populations become denser.
Bacteria and biological control
Bacteria used for biological control infect insects via their digestive tracts, so insects with sucking mouth parts like aphids and scale insects are difficult to control with bacterial biological control.
Bacillus thuringiensisBacillus thuringiensis is a Gram-positive, soil-dwelling bacterium, commonly used as a pesticide. Additionally, B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on the dark surface of plants.-Discovery and Study:B...
is the most widely applied species of bacteria used for biological control, with at least four sub-species used to control
LepidopteraLepidoptera is an order of insects that includes moths and butterflies. It is one of the most speciose orders in the class Insecta, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
n (
mothA moth is an insect closely related to the butterfly, both being of the order Lepidoptera. The differences between butterflies and moths are more than just taxonomy. Sometimes the names "Rhopalocera" and "Heterocera" are used to formalize the popular distinction...
,
butterflyA butterfly is an insect of the order Lepidoptera. Like all Lepidoptera, butterflies are notable for their unusual life cycle with a larval caterpillar stage, an inactive pupal stage, and a spectacular metamorphosis into a familiar and colourful winged adult form. Most species are day-flying so...
), Coleopteran (beetle) and Dipteran (true flies) insect pests.
Fungi and biological control
Fungi that cause disease in insects are known as entomopathogenic fungi, including at least fourteen species of entomophthoraceous fungi attack aphids. Species in the genus
TrichodermaTrichoderma is a genus of fungi 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....
are used to manage some soilborne plant pathogens.
Plants to regulate insect pests
Choosing a diverse range of plants for the garden can help to regulate pests in a variety of ways, including;
- Masking the crop plants from pests, depending on the proximity of the companion or intercrop.
- Producing olfactory inhibitors, odors that confuse and deter pests.
- Acting as trap plants by providing an alluring food that entices pests away from crops.
- Serving as nursery plants, providing breeding grounds for beneficial insects
Beneficial insects 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 outcomes from a human perspective...
.
- Providing an alternative habitat, usually in a form of a shelterbelt
A windbreak or shelterbelt is a plantation 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 around the edges of fields on farms. If designed properly, windbreaks around a...
, hedgerow, or beetle bankIn agriculture, a beetle bank is a strip of grass or perennial plants in a field that provide habitat which fosters and provides cover for insects hostile to pests.They are used as a form of biological pest control to reduce or replace the use of insecticides....
where beneficial insects can live and reproduce. Nectar-rich plants that bloom for long periods are especially good, as many beneficials are nectivorous during the adult stage, but parasitic or predatory as larvae. A good example of this is the soldier beetle which is frequently found on flowers as an adult, but whose larvae eat aphids, caterpillars, grasshopper eggs, and other beetles.
Plants to regulate plants
The
legumeIn botanical writing legume is a plant in the family Fabaceae , or a fruit of these specific plants. A'legume' fruit is a simple dry fruit that develops from a simple carpel and usually dehisces on two sides. A common name for this type of fruit is a pod, although "pod" is also applied to a few...
vine
Mucuna pruriensMucuna pruriens is a tropical legume known by a multitude of common names .-Common names:* Velvet bean* Cowitch* Cowhage* Juckbohne * Picapica* Kapikachu* Yerepe * Atmagupta...
is used in the countries of
BeninBenin , officially the Republic of Benin, is a country in West Africa. It borders Togo to the west, Nigeria to the east and Burkina Faso and Niger to the north; its short coastline to the south leads to the Bight of Benin....
and
VietnamVietnam , officially the Socialist Republic of Vietnam , is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea to the east...
as a biological control for problematic
Imperata cylindrica grass.
Mucuna pruriens is said not to be invasive outside its cultivated area.
Directly introducing biological controls
Most of the biological controls listed above depend on providing incentives in order to 'naturally' attract beneficial insects to the garden. However there are occasions when biological controls can be directly introduced. Common biocontrol agents include parasitoids, predators, pathogens or weed feeders. This is particularly appropriate in situations such as the greenhouse, a largely artificial environment, and are usually purchased by mail order.
Some biocontrol agents that can be introduced include;
- Encarsia formosa. This is a small predatory chalcid wasp
Chalcid wasps belong to the insect order Hymenoptera, and are one of the largest groups within the order, with some 22,000 known species, and an estimated total diversity of anywhere from 60,000 to more than 500,000 species, meaning the vast majority have yet to be discovered and described.Most of...
which is parasitical on whiteflyThe whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
, a sap-feeding insect which can cause wilting and black sooty mouldSooty molds are Ascomycete fungi which grow from the sugary honeydew secreted by plants and insects aphids, scales, the whitefly, and other insects which suck sap from their host plants. The name itself is descriptive, as sooty mold is a black, powdery coating on the leaves of ornamentals such as...
s. 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 pupates. It should be introduced as soon as possible after the first adult whitefly are seen. Should be used in conjunction with insecticidal soapInsecticidal soap is defined as any of the potassium fatty acid soaps used to control many plant pests. Insecticidal soap is typically sprayed on plants in the same manner as other insecticides. Insecticidal soap works only on direct contact with the pests. The fatty acids disrupt the structure and...
.
- Red spider mite, another pest found in the greenhouse, can be controlled with the predatory mite Phytoseilus persimilis. This is slightly larger than its prey and has an orange body. It develops from egg to adult twice as fast as the red spider mite and once established quickly overcomes infestation.
- A fairly recent development in the control of slug
Slug is a common word, normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell, in contrast to snails, which are gastropods with coiled shells that are big enough to retract into. All slugs are descended from snails that gradually lost...
s is the introduction of 'Nemaslug', a microscopic nematodeThe "roundworms" or "nematodes" are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 80,000 have been described, of which over 15,000 are parasitic. It has been estimated that the total number of...
(Phasmarhabditis hermaphrodita) which will seek out and parasitize slugs, reproducing inside them and killing them. The nematode is applied by watering onto moist soil, and gives protection for up to six weeks in optimum conditions, though is mainly effective with small and young slugs under the soil surface.
- A bacterial biological control which can be introduced in order to control butterfly caterpillars is Bacillus thuringiensis
Bacillus thuringiensis is a Gram-positive, soil-dwelling bacterium, commonly used as a pesticide. Additionally, B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on the dark surface of plants.-Discovery and Study:B...
. This available in sachets of dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicaBrassica is a genus of plants in the mustard family . The members of the genus may be collectively known either as cabbages, or as mustards...
s and fruit treeA fruit tree is a tree bearing fruit that is consumed or used by people — all trees that are flowering plants produce fruit, which are the ripened ovary of a flower containing one or more seeds. In horticultural usage, the term 'fruit tree' is limited to those that provide fruit for human food...
s. The bacterial disease will kill the caterpillars, but leave other insects unharmed. There are strains of Bt that are effective against other insect larvae. Bt israelensisBacillus thuringiensis serovar israelensis is a group of bacteria used as biological control agents for larvae stages of certain Dipterans. Bti produces toxins which are effective in killing various species of mosquitoes, fungus gnats, and blackflies, while having almost no effect on other...
is effective against mosquitoMosquito is a common insect in the family Culicidae...
larvae and some midges.
- A viral biological control which can be introduced in order to control the overpopulation of European rabbit
The European Rabbit is a species of rabbit native to south west Europe . It has been widely introduced elsewhere often with devastating effects on local biodiversity...
in Australia is the rabbit haemorrhagic disease virusRabbit haemorrhagic disease virus , also known as rabbit calicivirus , is the type species of the genus Lagovirus belonging to Caliciviridae family. RHDV is an important pathogen that causes a highly contagious disease in wild and domestic rabbits, rabbit haemorrhagic disease...
that causes the rabbit haemorrhagic diseaseRabbit haemorrhagic disease , also known as rabbit calicivirus disease or viral haemorrhagic disease , is a highly infectious and often fatal disease that affects rabbits of the species Oryctolagus cuniculus...
.
- A biological control being developed for use in the treatment of plant disease is the fungus
A fungus is any member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. The Fungi are classified as a kingdom that is separate from plants, animals and bacteria...
Trichoderma viride. This has been used against Dutch Elm diseaseDutch elm disease is a fungal disease of elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, the disease has been accidentally introduced into America and Europe, where it has devastated native populations of elms which had not had the opportunity...
, and to treat the spread of fungal and bacterial growth on tree wounds. It may also have potential as a means of combating silver leaf diseaseChondrostereum purpureum is a fungal plant pathogen which causes the Silver leaf disease of fruit trees; plums are especially vulnerable .In the past the name Stereum purpureum Pers...
.
- Several species of dung beetle
Dung beetles are beetles that feed partly or exclusively on faeces. All of these species belong to the superfamily Scarabaeoidea; most of them to the subfamilies Scarabaeinae and Aphodiinae of the family Scarabaeidae. This beetle can also be referred to as the scarab beetle. As most species of...
were introduced to Australia from South Africa and Europe during the Australian Dung Beetle ProjectThe Australian Dung Beetle Project , conceived and led by Dr. George Bornemissza, of the Commonwealth Scientific and Industrial Research Organisation , was an international scientific research and biological control project with the primary goal to introduce foreign species of dung beetle to...
(1965-1985) led by Dr. George BornemisszaGeorge Francis Bornemissza is a Hungarian-born entomologist and ecologist. He studied science at the University of Budapest before obtaining his PhD in zoology at the University of Innsbruck in Austria in 1950. At the end of that year he emigrated to Australia...
of the Commonwealth Scientific and Industrial Research OrganisationThe Commonwealth Scientific and Industrial Research Organisation is the national government body for scientific research in Australia...
in order to biologically control the population of pestilent bush flies and parasitic worms.
- The parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism which it ultimately kills in the process. Thus they are similar to typical parasites except in the certain fate of the host. In a typical parasitic relationship, the...
Gonatocerus ashmeadi (Hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees, and ants. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and πτερόν : wing...
: Mymaridae) has been introduced to control the glassy-winged sharpshooterThe glassy-winged sharpshooter is a large leafhopper insect from the family Cicadellidae, similar to other species of sharpshooter. It is about half an inch in length. Its color is dark brown to black with a black-and-yellow underside...
Homalodisca vitripennis (Hemipterae: Cicadellidae) in French PolynesiaFrench Polynesia is a French overseas collectivity in the southern Pacific Ocean. It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...
and has successfully controlled ~95% of the pest density
Negative results of biological pest control
In some cases, biological pest control can have unforeseen negative results that could outweigh all benefits. For example, when the
mongooseMongooses are a family of about 30 species of small carnivorans from southern Eurasia and mainland Africa. Four additional species from Madagascar in the subfamily Galidiinae, which were previously classified in this family, are also frequently referred to as "mongooses"...
was introduced to
HawaiiHawaii is the newest of the 50 U.S. states, and is the only state made up entirely of islands. It is located on an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of Australia. The state was admitted to the Union on August...
in order to control the
ratRats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
population, it preyed on the
endemic birds of HawaiiThis article is one of a series providing information about endemism among birds in the World's various zoogeographic zones. For an overview of this subject see Endemism in birds....
, especially their
eggsIn most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo. When the embryo is adequately developed it breaks out of the egg in the...
, more often than it ate the rats.
Cane toads (
Bufo marinus) were introduced to
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
in the 1930s in a failed attempt to control the cane beetle, a pest of sugar cane crops. 102 toads were obtained from
HawaiiHawaii is the newest of the 50 U.S. states, and is the only state made up entirely of islands. It is located on an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of Australia. The state was admitted to the Union on August...
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 can't jump very high so they did not eat the cane beetles which stayed up on the upper stalks of the cane plants. The toads soon became very numerous and out-competed native species and became very harmful to the Australian environment, including being very toxic to would-be predators such as native snakes.
http://fdrproject.org.au/pages/toads.htm
See also
- Association of Natural Biocontrol Producers
The Association of Natural Biocontrol Producers is an international not-for-profit professional association representing the biological pest management industry....
- Biological pesticide
The term biopesticide is used for microbial biological pest control agents that are applied in a similar manner to chemical pesticides. Commonly these are bacterial, but there are also examples of fungal control agents, including Trichoderma spp. and Ampelomyces quisqualis . Bacillus subtilis...
- Chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...
(Natural Biocontrol for Agricultural & Horticultural use)
- Insectary plants
Insectary plants is a term used to describe plants that attract insects. As such, beneficial insectary plants are intentionally introduced into an ecosystem to increase pollen resources and nectar resources required by the natural enemies of harmful or unwanted insect pests...
- Integrated Pest Management
In agriculture, integrated pest management is a pest control strategy that uses a variety of complementary strategies including: mechanical devices, physical devices, genetic, biological, cultural management, and chemical management. These methods are done in three stages: prevention, observation,...
- Japanese beetle
The beetle species Popillia japonica is commonly known as the Japanese beetle. It is about 1.5 cm long and 1 cm wide, with iridescent copper-colored elytra and green thorax and head...
(article includes information on biological control methods)
- Organic farming
Organic farming is the form of agriculture that relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation etc.....
- Pest control
Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
- Sterile insect technique
Sterile insect technique is a method of biological control, whereby millions of sterile insects are released. The released insects are normally male as it is the female that causes the damage, usually by laying eggs in the crop, or, in the case of mosquitoes, taking a bloodmeal from humans. The...
- Mating disruption
Mating disruption is a pest management technique designed to control certain insect infestations. Specifically, mating disruption involves the utilization of synthesized sex pheromones to disrupt the reproductive cycle of insects.- Mechanism:...
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