File Name: biological control of insect pests and weeds .zip
Classical biological control CBC is the introduction of a natural enemy of exotic origin to control a pest, usually also exotic, aiming at permanent control of the pest. CBC has been carried out widely over a variety of target organisms, but most commonly against insects, using parasitoids and predators and, occasionally, pathogens.
For information about UMaine Extension programs and resources, visit extension. Find more of our publications and books at extensionpubs. Biological control is the use of living organisms to suppress pest populations, making them less damaging than they would otherwise be.
For information about UMaine Extension programs and resources, visit extension. Find more of our publications and books at extensionpubs. Biological control is the use of living organisms to suppress pest populations, making them less damaging than they would otherwise be. Biological control can be used against all types of pests, including vertebrates, plant pathogens and weeds as well as insects. The methods and agents used are different for each type of pest. This fact sheet focuses on the biological control of insects and related organisms.
Pests are only a tiny fraction of the insect species around us. Many pest species only occasionally do real damage. Natural enemies play an important role in limiting potential pest populations.
We have seen what happens when pesticides devastate the natural enemies of potential pests. Insects that were of little economic importance can become damaging pests.
When a non-toxic control method is used, natural enemies are more likely to survive and reduce the numbers and damage of potential pest species. Many kinds of predators feed on insects. Insects are an important food for many vertebrates, including birds, amphibians, reptiles, fish and mammals. Insect and related predators are more often used in biological control because they feed on a smaller range of prey species.
These predators, with their shorter life cycles, may also fluctuate in population density in response to changes in the density of their prey. Important insect predators include lady beetles, ground beetles, rove beetles, flower bugs and other predatory true bugs, lacewings and hover flies.
Spiders and some families of mites are also predators of insects and mite pests. Parasitoids are insects with an immature stage that develops on or in an insect host, and ultimately kills the host. Adults are typically free-living, and may be predators. They may also feed on other resources, such as honeydew, plant nectar or pollen.
Because parasitoids must be adapted to the life cycle, physiology and defenses of their hosts, many are limited to one or a few closely related host species.
Thus, accurate identification of the host and parasitoid species is very important if you use parasitoids for biological control. Insects, like other animals and plants, are infected by bacteria, fungi, protozoans and viruses that cause disease. These diseases may reduce the rate of feeding and growth of insect pests, slow or prevent their reproduction, or kill them.
In addition, insects are also attacked by some nematodes that, along with the bacteria they carry, cause disease or death. Under certain conditions, diseases can multiply and spread naturally through an insect population, particularly when the density of the insects is high.
An example of an insect pathogen that has been successfully controlling its host is the fungus Entomophaga maimaiga , a pathogen of the gypsy moth. This fungus was introduced about , but was not recovered in forests until , when it was widespread and abundant in New England. It has continued to control New England gypsy moth populations for several years.
It overwinters in leaf litter as resting spores, which germinate when gypsy moth larvae are present. Newly hatched caterpillars are dispersed by wind, and those that fall to the forest floor are probably infected while crawling to a tree. While these larvae are feeding in the tree canopy, if there is enough rainfall, the fungus in their bodies produces spores that spread to other caterpillars. If conditions are right, this infection cycle occurs again during the larval stage.
Large caterpillars rest during the day in forest litter, where they are also susceptible to infection. In late June, as infected caterpillars die in large numbers, new resting spores are produced to survive the next winter.
This biological control process depends on well-timed rainfall to be successful. Reducing pesticide use: Most natural enemies are highly susceptible to pesticides, so pesticides limit their effectiveness. The first step in reducing pesticide use is to develop economic thresholds and methods to monitor populations to see if they exceed thresholds. The need for pesticides can also be reduced by increasing the pest resistance of crop plants and animals, disrupting pest mating or host-finding behavior, and using cultural and physical methods to reduce pest numbers or their damage.
As you use fewer pesticides, you may increase the effectiveness of existing natural enemies against multiple pests.
So the benefit to the farmer may be much more than just saving the cost of the chemical and its application. Selecting and using pesticides to minimize the effect on natural enemies: The effect of a pesticide on natural enemy populations depends on the physiological effect of the chemical and on how the pesticide is used — how and when it is applied, for example. While insecticides and acaricides pesticides that kill mites and ticks are most likely to be toxic to insect and mite natural enemies, herbicides and fungicides are sometimes toxic as well.
A database has been compiled on the effects of pesticides on beneficial insects, spiders and mites summarized in Croft and Benbrook Among insecticides, synthetic pyrethroids are among the most toxic to beneficials, while Bacillus thuringiensis and insect growth regulators were among the least toxic. In general, systemic insecticides, which require consuming plant material for exposure, and insecticides that must be ingested for toxicity affect natural enemies much less than pests.
Pesticides may also have more subtle effects on the physiology of natural enemies than direct toxicity. Several fungicides, such as benomyl, thiophanate-methyl and carbendazim, inhibit egg laying by predacious phytoseiid mites. Certain herbicides diquat and paraquat make the treated soil in vineyards repellent to predacious mites.
The impact of pesticides on natural enemies can be reduced by careful timing and placement of applications. The goal is to minimize contact between the beneficial organism and the pesticide. Spot applications in areas of high pest density may control the pest without hurting natural enemies in nearby areas. However, this might not work well if the natural enemies are concentrated in or move through the treated area.
Unless they are re-released each year, they must have a suitable environment for overwintering. Some parasitoids and pathogens overwinter in the bodies of their hosts which may have overwintering requirements of their own.
Others may pass the winter in crop residues, other vegetation or in soil. A classic example is the overwintering of predacious mites in fruit orchards. Ground cover in these orchards provides shelter over the winter, refuge from pesticides used on the fruit trees, and a source of pollen and alternate prey.
Many adult predators and parasitoids may need or benefit from pollen, nectar or honeydew produced by aphids during the summer. Many crop plants flower for only a short time, so flowering plants along the edges of the field or within the field may be needed for pollen and nectar.
However, having many different types of plants in the field can also prevent insects, especially some parasitoids, from finding hosts. Populations of generalist predators may stabilize because of ample pollen and prey. But their effectiveness still depends on whether they respond quickly enough to outbreaks of the target pest.
Thus, adding plants or other food sources for natural enemies must be done with knowledge of the behavior and biology of the natural enemy and pest.
For example, the pink-spotted lady beetle Coleomegilla maculata can be an important predator of Colorado potato beetle eggs and larvae. It depends on the availability of aphid prey in crop fields, including crops of alfalfa, brassicas, cucurbits, and corn. It also depends on the availability of pollen from corn or other plants, such as dandelion and yellow rocket.
Although this predator does not control Colorado potato beetle on its own, if we knew more about managing C. This process requires extensive research into the biology of the pest, potential natural enemies and their biology, and possible unintended consequences e. After suitable natural enemies are found, studied and collected, they must undergo quarantine to eliminate any pathogens or parasites on the natural enemy population.
Then, the natural enemies are carefully released, timing their arrival with the enemy pest life cycle, in a site where the target pest is abundant, and where they will do well. Although this process is long and complex, when it is successful, the results can be impressive and permanent. One of many examples of a pest controlled by successful introduction of natural enemies is the alfalfa weevil.
The alfalfa weevil is native to Europe, and was first reported in the United States in It appeared in the eastern United States about , and by the s was a major pest across the country. Larval densities were high enough to require most growers to spray one or more times per year. Several parasitoids were introduced against the weevil. The most successful were two species of parasitoids that attacked the larvae, one that attacked the adult, and a parasitoid and predator that attacked the eggs.
In addition, there was a control program to collect natural enemies, rear them in large numbers, and release them. These natural enemies, plus a fungal disease that infects larvae and pupae, has kept weevil densities in the Northeast far below the economic injury levels. The success of this biological control was enhanced by cultural methods, such as timing cuttings to reduce weevil populations and avoid disruption of natural enemies.
In addition, introductions of other natural enemies of alfalfa pests and pest-resistant alfalfa varieties minimized insecticide use against alfalfa blotch leafminer and aphids. This also allowed natural enemies of alfalfa weevil to flourish. Natural enemies that are repeatedly released require more direct investment and involvement by the farmer. Effectiveness depends on timing and compatible environmental conditions. In other cases, such as in greenhouses, natural enemy habitats are shut down at the end of the season or production cycle.
So with annual crops, or in seasonal systems, the natural enemy may need to be reintroduced regularly to control pests. In an inoculative release, the natural enemy should reproduce itself throughout the season and eventually reach a balance with the pest population.
Seasonal inoculative release of insect parasitoids and predators has been a highly successful strategy for biological control in European greenhouses. The program was originally built around use of the parasitoid Encarsia formosa against the greenhouse whitefly and the predacious mite Phytoseiulus persimilis against the two-spotted spider mite. Over the years, additional natural enemies have been added to control other pests, such as thrips, leafminers, aphids, caterpillars and other whitefly species.
Biological control costs are now much lower in Europe than chemical control costs. Growers learn about programs, new developments and new natural enemies through a network of extension advisers, specialized journals and grower study groups. Another example of seasonal inoculative release in the field is the use of the parasitic wasp, Pediobius foveolatus against Mexican bean beetles.
These parasitoids can not survive Northeast winters. However, they can be reared in the laboratory and released annually, where they multiply, killing their hosts throughout the season. They are reared and released and are also commercially available. Biological insecticides or inundative release: These two approaches are fundamentally different from all the other approaches to biological control because they do not aim to establish a population of natural enemies that reaches a long-term balance with host or prey population.
Carlos Henrique Marchiori 1. Biological control is a component of an integrated pest management strategy. It is defined as the reduction of pest populations by natural enemies and typically involves an active human role. Keep in mind that all insect species are also suppressed by naturally occurring organisms and environmental factors, with no human input. This is frequently referred to as natural control. This guide emphasizes the biological control of insects but biological control of weeds and plant diseases is also included. Natural enemies of insect pests, also known as biological control agents, include predators, parasitoids, and pathogens.
Environmental stewardship and food security are the most important factors that involved in agriculture. In many cases by the misuse of insecticide led to population resurgence, pesticide residues, and pest resistance. The microorganisms like virus, fungus, protozoan or bacterium are the active ingredient in this type of pesticides. Safety of food alludes to the conditions and practices that save the quality of food to anticipate tainting and food borne sicknesses. Natural enemies and botanicals play a vital role to control pests with different mechanisms. Microbial, for example, microscopic organisms, growths, and infections are the major biopesticides being concentrated generally to create contrasting options to chemicals.
Biological control or biocontrol is a method of controlling pests such as insects , mites , weeds and plant diseases using other organisms. It can be an important component of integrated pest management 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, parasitoids , pathogens , and competitors. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators, herbivores , and plant pathogens. Biological control can have side-effects on biodiversity 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.
This segment includes several paragraphs with general information about biological control and these subsections:. Biological control is a component of an integrated pest management strategy. It is defined as the reduction of pest populations by natural enemies and typically involves an active human role.
Наверное, эта женщина - ангел. Она прилетела за. Ангел заговорил: - Дэвид, я люблю. Внезапно он все понял. Сьюзан на экране тянулась к нему, плача и смеясь, захлестнутая волной эмоций. Вот она вытерла слезы.
- Стратмор уже солгал нам. - Она окинула Бринкерхоффа оценивающим взглядом. - У тебя есть ключ от кабинета Фонтейна. - Конечно. Я же его личный помощник.
Мужчина нерешительно кивнул. Беккер заговорил на чистейшем немецком: - Мне нужно с вами поговорить. Мужчина смотрел на него недовольно. - Was wollen Sie. Что вам .
Но потом поняла, куда смотрел коммандер: на человеческую фигуру шестью этажами ниже, которая то и дело возникала в разрывах пара. Вот она показалась опять, с нелепо скрюченными конечностями. В девяноста футах внизу, распростертый на острых лопастях главного генератора, лежал Фил Чатрукьян. Тело его обгорело и почернело. Упав, он устроил замыкание основного электропитания шифровалки.
Неужели Стратмор каким-то образом проскользнул наверх. Разум говорил ему, что Стратмор должен быть не наверху, а внизу. Однако звук повторился, на этот раз громче. Явный звук шагов на верхней площадке.
АНБ, перехватывая эти информационные импульсы, игнорировало их, считая аномалией сети, безобидной тарабарщиной. Но когда ТРАНСТЕКСТ расшифровал эти потоки информации, аналитики тут же увидели в них синхронизированный через Интернет отсчет времени. Устройства были обнаружены и удалены за целых три часа до намеченного срока взрыва.
Сьюзан подумала о Стратморе, о том, как мужественно он переносит тяжесть этого испытания, делая все необходимое, сохраняя спокойствие во время крушения. Иногда она видела в нем что-то от Дэвида. У них было много общего: настойчивость, увлеченность своим делом, ум.
Your email address will not be published. Required fields are marked *