Biological Pest Control — an overview, ScienceDirect Topics

Biological Pest Control

Biological control is the release of an organism that will consume or attack a pest species resulting in a population decrease to a level where it is no longer considered a pest.

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Novel Approaches for Reversible Field Releases of Candidate Weed Biological Control Agents


Biological control programs for weeds are coming under increased scrutiny by environmental groups in the USA. Legal challenges not only have stopped the release and redistribution of one group of biological control agents for weeds, but also have apparently delayed the issuance of permits for other biological control agents that have been recommended for field release. In this paper, three experimental approaches are described for predicting the field host specificity of some biological control candidates for weeds in the proposed country of introduction without any risk of permanent establishment of the insects. All three approaches are based on scientifically proven concepts and will facilitate biological control releases on an experimental basis before full-scale implementation.

Biological Control in Deciduous Fruit Crops


Biological control research and implementation for pests of deciduous tree fruits have for the past quarter century tended to emphasize augmentation and conservation of natural enemies associated with secondary indirect pests of these crops such as mites, aphids, leaf miners, scales, and leafhoppers. Population dynamics and biological control effectiveness of the natural enemies associated with these pests have been studied in some detail. Efforts also have been made to develop selective uses of registered pesticides and/or to identify physiologically selective pesticides for control of pest species (e.g., note the many examples of identification of selective acaricides to date). Use of resistant beneficials has had a major impact on the selective use of pesticides on tree fluit crops, especially with the organophosphate insecticides.

Research on classical biological control of primary direct pests of these crops has been limited, although several outstanding successful cases of biological control have been reported (e.g., winter moth, woolly apple aphid, and others). In the future, a balance between research with conservation and augmentation of native natural enemies versus classical biological control studies of imported pests of these crops should be sought. Unfortunately, it is more difficult to support these more long-term studies of foreign exploration, importation, and establishment of exotics than it is to work with better management of already established forms of predators or parasitoids. Major efforts should be made to emphasize the importance of these more costly but highly rewarding approaches to biological control of pests on these crops and the follow-up evaluations that are necessary to document their value and effectiveness in the future.

Biological Control of Weeds in Terrestrial and Aquatic Environments


Biological control is the study of relationships among weeds, their associated organisms, and the environment, followed by the manipulation of selected species of these organisms (natural enemies) to the detriment of a target weed species. Attention is focused on those weed–natural enemy relations that have coevolved to the degree that the weed’s natural enemies cannot exist or would have little environmental impact in the absence of their host. In other words, coevolved natural enemies that have developed a high degree of host specificity have proven the safest to use, are least likely to damage nontarget plant species, and are most suitable for regulating weed abundance. Biological control scientists go to considerable effort to match natural enemies to their weedy host plants in problem environments, seeking combinations and devising manipulations most detrimental to the weeds.

The natural enemies used in biological control are self-perpetuating only in the presence of their weed hosts and then only within the limits set by the environment. According to definitions for biological control offered by Smith (1919 , 1948 ) and DeBach (1964) , the ability of natural enemies to regulate weed or pest arthropod populations in a self-sustaining, density-dependent manner sets biological control apart from other methods of control.

Polyphagous agents (plant-feeding fish, sheep, cattle, geese, and other grazing animals) are useful in removing weeds in some situations (see later), but their numbers and actions must be carefully regulated to avoid damage to nontarget plants. Although these vertebrate grazers remove unwanted foliage, their inability to selectively regulate weed numbers limits their use in biological control.

Whither Hence, Prometheus?

Combating Adventive and Native Pests

Biological control clearly holds great promise for solutions to pest problems affecting agricultural. The ecological principles that underlie biological control in both managed and natural ecosystems do not change with the passage of time; they are basic to interactions among species. Consequently, biological control continues to provide productive, efficient, and economical solutions to pest problems. The record to date indicates that biological control is of significant value and widely successful, providing either partial or complete control in 60% of the cases were it has been used ( Greathead & Greathead, 1992 ). Adventive insects make up a large portion of the world’s most serious pests ( Van Driesche & Bellows, 1996 ), yet biological control has been applied against only 5% of the world’s pest species ( Van Driesche & Ferro, 1987 ). With a 60% success rate and 95% of pest species still waiting to be addressed, this is clearly a field where application will bear a marvelous return on investment.

New biological control efforts are currently needed for many existing pest problems, both for programs targeted against introduced pests and for additional work toward natural-enemy conservation in pest management systems. International man-assisted movement of plant material and insect pests will likely continue, and cause the unintentional eruption of new pests by shipping pest species to new locations while separating them from their natural enemies. Such pests eruptions will require research and action to locate and introduce natural enemies suitable for limiting the pests in their new environments. The dependence of civilization on agriculture, both in developed and developing countries, continues to press the need for integrated management systems for efficient and economical production. Such integrated systems increasingly rely on natural enemies to reduce both costs and pesticide use.

Conservation Biological Control and Biopesticides in Agricultural☆

Conservation biological control is the modification of the environment or of agronomic practices to protect and enhance the efficacy of natural enemies of pest organisms. Biopesticides are natural enemies of pest organisms released en masse to control the pest, where the agent does not usually persist in high numbers in the crop environment. These two methods are the two most recent forms of biological control and are relatively early in their developmental stages. However, these techniques are proving to have potential as effective tools in pest management and do not carry the sometimes high risks of classical biological control. This article will not concentrate on conservation biological control or biopesticides in particular crops, pest species, or diseases. Rather, it will assess the theories involved, progress to date, and prospects for further adoption of these practices and products.

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Application to Sustainability of Ecosystem Services

5.2 Biological Control

Biological control is an essential regulatory service that typically is undervalued until lost. The consequences of predator removal programs (often intended to increase populations of game animals) were so severe (overabundances of starving game species) that predator reintroduction programs have been required to restore the role of predators in regulation of healthy, stable prey populations ( Peterson, 1999; Wilmers et al., 2006 Peterson, 1999 Wilmers et al., 2006 ). Diversity of insectivorous birds and mammals provides important regulation of insect prey, including many pest species ( B. Allan et al., 2009 ; M.D. Johnson, 2000 ; M.D. Johnson et al., 2009, 2010 ; C.G. Jones et al., 1998 ; Kellermann et al., 2008 , see the following section and Chapters 8 and 17 8 17 ). Similarly, insects frequently have been instruments of biological control for other insects or invasive weeds (see Chapter 17 ). L. Thomson and Hoffman (2010) reported that biological control of insect pests was enhanced when vinyards were surrounded by natural remnant forest or planted woody vegetation, compared to no woody vegetation.

Arthropods and Vertebrates in Biological Control of Plants


Biological control of plants using insect and other metazoan herbivores has a long history of research and application throughout the world. Some of the world’s worst weed pests, both terrestrial and aquatic, have been controlled biologically with herbivores. In many of these cases, biological control has been the only possible option, for example, in cases where weeds become naturalized over millions of hectares of native grasslands or colonize natural waterways. Although cultural and chemical control cannot address the presence of a huge, self-reproducing population over vast areas, the use of natural control agents has often proved beneficial and effective.

In the context of “use” of herbivorous insects, mites, nematodes, and vertebrates, we are almost exclusively concerned with the introduction of a herbivore to control either an adventive or a native plant pest. In such work, herbivores become candidate “agents” for use against a particular target weed. As this field has developed, the majority of cases have involved the discovery and release of herbivores into the environment to become naturally reproducing populations; the use of large numbers of mass-reared individuals, as is sometimes done with parasitoids or predators against other insect pests, has found only very limited application in the control of weeds. Thus, we are concerned here with the ecological context of introducing new herbivore species (through the usual channels of strict quarantine and evaluation, see Chapters 5 and 6 ) into environments as permanent members of the new community, with the aim that their presence will reduce the damage caused by a weedy plant. In most cases, the target weed will be adventive, or introduced , into the target environment. The work of biological control of weeds with invertebrates thus involves three broad fields of endeavor: research into plant biology and ecology, herbivore biology and ecology, and herbivore–plant interactions.

In this volume there are two additional chapters that address biological control of weedy plants. Chapter 34 reviews programs against both aquatic and terrestrial weeds from a programmatic viewpoint. Chapter 35 reviews the use of plant pathogens as agents against weedy plants. This chapter reviews the use of invertebrates and vertebrates in plant biological control programs and discusses the taxa that have been used in these programs. We touch briefly on ecological attributes of biological control agents, and review procedures for ensuring the ecological safety of candidate natural enemies.

Biological Control of Forest Insects


Biological control of forest insects has been most prevalent in temperate and Mediterranean regions. This primarily reflects the regions of more extensive and actively managed commercial forests and the regions where forest pests have been accidentally introduced by trade and travel.

There are no organizations devoted solely to the biological control of forest insects. However, the Canadian Department of Agriculture Laboratory at Belleville, and an international organization, the CAB IIBC, formerly the Commonwealth Institute of Biological Control, have devoted a portion of their efforts to forest insects.

Normally projects are organized around the target pest and a project group is created involving federal, state or province, and private agencies. The Sirex project in Australia and the gypsy moth and European spruce sawfly projects in the United States are good examples. In both Australia and the United States there are government agencies in place that are responsible for importation and quarantine but not specifically for forest insects. These agencies, however, participate whenever a forest insect biological control program is initiated.


In Australia, commonwealth and state ministers met in 1962 and created a national Sirex fund. All states contributed approximately in proportion to their acreage of pine and this was matched by the commonwealth government ( Taylor, 1981 ). Private forest owners also contributed to the Sirex fund that was administered by a committee that coordinated research as well as the practical operations. A number of organizations were involved in the program, including the Divisions of Entomology and of Forest Research of Commonwealth Scientific and Industrial Research Organization (CSIRO); the Waite Agricultural Research Institute, University of Adelaide; the Forest Research Institute, New Zealand; Forest Commission of Victoria and Tasmania; and the University of Tasmania. The IIBC also participated in this project. The biological control program against bark beetle Ips grandicollis (Eichoff) in Australia from 1981 to 1990 was organized in a similar way, with private timber companies and government agencies participating in the funding. It was nationally funded by the state forest services from 1983 to 1990 ( Forest Insect Pest Management Association, 1992 ).

United States

In the United States, the Animal and Plant Health Inspection Service (APHIS) of the U. S. Department of Agriculture (USDA) is responsible for controlling the importation of living insect material into the United States. Formerly this responsibility resided in other federal organizations, the Federal Entomology Research Branch and the Bureau of Entomology and Plant Quarantine. The forest biological control projects are normally in cooperation with state agencies and other federal agencies such as the Forest Service and the Agricultural Research Service (ARS).

Generally, importation activities are restricted to the federal government agency and ARS Beneficial Insects Research Laboratory maintains quarantine facilities. The states participate in all the other biological control activities. The one exception to the restriction on importation activities is the state of California. California began importation on an independent basis in 1899 and maintains its own quarantine facilities for receiving insects and mites ( Clausen, 1956 ).

Some examples of early cooperative programs were the natural-enemy studies of the gypsy moth and brown-tail moth that were conducted in Europe when the Massachusetts State Board of Agriculture paid the cost of the foreign exploration by federal personnel. In later releases, the New Jersey Department of Agriculture (NJDA) cooperated with APHIS in distributing parasitoids. The gypsy moth biological control program was one of the largest and most extensive projects in the United States. In the biological control program against the European spruce sawfly in the United States, the Canadian Department of Agriculture provided large stocks of parasitoids that were reared and distributed by the Federal Bureau of Entomology and Plant Quarantine and the State of Maine Forest Service. Because there is not a specific agency for forest biological control in the United States, the programs—always cooperative projects between APHIS, ARS, forest insect researchers in the U.S. Forest Service, and entomologists at universities—involve other state and federal agencies in the implementation phase.

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The evolution of biological control programs and laboratories in Canada has been reviewed by Beirne (1973) . The first introductions of natural enemies against forest pests were conducted by C. G. Hewitt, the second dominion entomologist, who arranged for parasitoid collections in England for use against the larch sawfly in 1910 to 1913. In 1912, the Natural Control Investigations Laboratory was established under J. D. Tothill in Fredericton to combat the invasion of the brown-tail moth in eastern provinces.

Subequently biological control programs were transferred to Belleville, Ontario, where the Dominion Parasite Laboratory was established by the Division of Entomology, Canadian Department of Agriculture under the charge of A. B. Baird in 1929. A 40-room, controlled environment quarantine building was added in 1936 and this provided the necessary facilities for the mass-rearing of imported parasitoids that were released on a massive scale against forest pests between 1934 and 1949. The Belleville Laboratory was responsible for the biological control programs against forest insects between 1929 and 1954, covering the period of peak activity ( Embree & Pendrel, 1986 ) and dramatic successes in the use of natural enemies to control introduced forest insects.

Interest in the potential of insect pathogens for the biological control of forest insects developed in the 1940s as a result of the successful introduction of the viral disease of the European spruce sawfly, and this led to the establishment in 1950 of the Insect Pathology Research Institute (now known as the Forest Pest Management Institute) in Sault Ste. Marie, Ontario. Then in 1954, an agreement was made to transfer the responsibility for biological control of forest pests from the Belleville Laboratory to the Forest Insect and Pathology Unit, headed by M. L. Prebble, with the Belleville Laboratory continuing to handle the quarantined importation of natural enemies from abroad.

From this time the biological control projects became dispersed to the regional research centers of the Forestry Service. With the closure of the Belleville Laboratory in 1972, quarantine facilities moved to Ottawa and currently biological control groups are most active, with their own quarantine laboratories, at the Pacific Forest Center in Victoria, British Columbia and the Great Lakes Forest Center in Sault Ste. Marie, Ontario. Canadian perspectives on the biological control of forest insect pests are provided by Hulme (1988) , Nealis (1991) , and Smith (1993) .

International Institute of Biological Control

The CAB International Institute of Biological Control (IIBC) has been active in the foreign exploration for natural enemies of forest insects in Europe for introduction into Canada, New Zealand, and the United States ( Greathead, 1980 ). This institute was established in 1927 as the Farnham House Laboratory in England, with W. R. Thompson as superintendent from 1928. In these early years much of the collection work was conducted in the United Kingdom or from field stations in France and Czechoslovakia.

In 1940, the difficulties of continuing operations in Europe during World War II led to the transfer of the Laboratory to Belleville, Canada, where it was renamed as the Imperial Parasite Service. After 6 years of being housed at the Belleville Laboratory, the headquarters moved to Ottawa and stations were opened in Trinidad, West Indies, and Fontana (near Riverside), California. Activities were resumed in Europe in 1947 with a station near Zurich in Switzerland, which moved to its present location in Delémont in 1962. F. J. Simmonds succeeded W. R. Thompson as director in 1958 and within a few years the headquarters was moved to Trinidad from Canada, where it remained until 1984. The headquarters is now situated at Silwood Park, the field station of the Imperial College of Science and Technology, London University, United Kingdom under the directorship of J. K. Waage, with regional stations in Europe, Africa, Asia, and the Caribbean. The institute has developed BIOCAT, the most complete database available on global biological control introductions of predators and parasitoids ( Greathead & Greathead, 1992 ).

Foreign exploration for parasitoids and predators of forest insects has been a major concern of the institute from its early years as the Farnham House Laboratory to current times at the Pakistan, European, and now U.K. stations, where forestry projects continue.

Social and Economic Factors Affecting Research and Implementation of Biological Control

JOHN H. PERKINS, RICHARD GARCIA, in Handbook of Biological Control , 1999


Biological control has a place in the most modern and sophisticated of pest control technologies, but researchers and advocates of the technology must be sensitive to the factors working against an easy transition to more reliance on biological control. Failure to be realistic about the social and economic factors weighing against use of biological control will, in the long run, be detrimental to the research enterprise. Despite the problems, several biological and cultural trends could improve biological control technology. An understanding of these trends could promote research and use of biological control in many areas.

Biological considerations of importance to biological control include problems associated with the use of pesticides: resistance, destruction of natural enemies accompanied by pest outbreaks, and damage to the health of nontarget organisms. Carson (1962) presented the first analysis of these problems, and many policy studies since her landmark work have confirmed the correctness of her thinking. Pesticide resistance and destruction of natural enemies often make chemicals technologically ineffective for the pest controller, thus providing an incentive to look elsewhere for relief from pest damage. Harm to nontarget organisms leads to more stringent regulations, which places the pest controller under severe political pressure to find an alternative. In either case, the biological control researcher can find an opportunity to provide a less dangerous mode of pest control, and the client audience of pest controllers will be a willing audience.

Cultural factors affecting the fortunes of biological control are more complex, than the biological considerations. The most important trends can be clustered into two main categories: regulatory and pricing. Many countries have increased regulation of activities related to pest control since the 1960s, mostly as a response to increased awareness of environmental and occupational hazards associated with pesticides. Regulations affecting the manufacture, sale, and use of pesticides are now common. In the United States, for example, the sale and use of pesticides were changed considerably in 1972 when the Federal Environmental Pesticide Control Act completely amended the 1947 Federal Insecticide, Fungicide, and Rodenticide Act. Explicit rules were authorized to protect nontarget organisms, and government regulators were ordered to consider the costs and benefits of the use of a prospective chemical before granting a license to sell and use it. The law was aimed at eliminating from use those chemicals for which environmental costs were out of proportion to benefits. Other legislation aimed to increase the safety of workers engaged in the manufacture of hazardous materials, including pesticides.

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The new laws affecting the manufacture, sale, and use of pesticides were an addition to older laws on the quality and purity of food products. Pesticide residues were regulated through the amendments to the Federal Food, Drug, and Cosmetic Act in 1953. Older parts of that act provided the authority to regulate marketed food for damages or remains of pests. The combination of regulations on pesticide residues and on the levels of pest damage permitted in food reflected a trade-off between the dangers posed by pesticide residues and those posed by the consumption of pest-damaged or contaminated food. Use of pesticides might provide damage-free, cosmetically perfect food products, but only at the expense of increased residues of chemicals on the food. No easy way exists to reconcile the relative danger of residues compared with insect contamination other than a case-by-case study of the particulars. Unfortunately, the ability of pesticides to produce cosmetically perfect food products created a standard in the marketplace for such produce and engendered habits within consumers for always demanding pest-free produce, which lacked visible damage but also contained the invisible residues of chemicals.

In 1996, Congress passed the Food Quality Protection Act, which amended the laws governing pesticide use and sales as well as residues of pesticides on food. Some of the major objectives of Congress were to provide better protection of children’s health from pesticides and to protect against growing concern that pesticides might disrupt endocrine systems of people and other animals ( Mintzer & Osteen, 1997 ). No evidence suggests that such safety regulations will abate in the future. Increasing research in toxicology continually finds damages from ever smaller exposures to hazardous substances, and an increasingly informed and sensitive public continues to demand protection through legislation.

Can this trend be utilized to promote research and implementation of biological control? Almost certainly yes, provided researchers and administrators seek the cases of toxicological hazard that are of most concern and design research programs that could “solve” the problem by creating an alternative technology less reliant on the chemicals. Judicious public relations with environmental and labor advocates could forge alliances to aid the biological control enterprise in the legislative arena.

Farming is very sensitive to price changes. Oil prices went up markedly in 1973 due to the actions of the Organization of Petroleum Exporting Countries (OPEC). Farmers’ expenses thus tended to rise for such essentials as fuel, fertilizers, and pesticides. Financial stress, sometimes considerable, was the result for farmers ( USDA, 1974 ). The shocks of OPEC price rises were sometimes dampened by government support subsidies to farmers, particularly in North America, Europe, and Japan. Instability in the OPEC cartel and energy conservation also produced some downward pressure on oil prices that provided limited relief to farmers ( Brown & Wolf, 1987 ). Nevertheless, the general trend in agriculture since 1973 has been for a squeeze between rising input and output prices. Increased grain production stemming from the modernization of agriculture in previously low-yield countries (e.g., India rapidly increased wheat output in the 1970s and 1980s) further exacerbated the pressure by forcing prices of major food commodities down in world markets ( International Institute for Environment and Development, 1987 ).

No evidence suggests that the pressure on profits of market-oriented agriculture will ease in the immediate future. Biological control, however, may play an increased role because of its cost-effectiveness. Classical and conservatory biological control are open to this line of argument, because purchased inputs are substituted by essentially “free” use of naturally reproducing biological control agents. Successful schemes allow the farmer to substitute a free input for an increasingly costly input. Provided the technology is reliable, the farmer has an economic incentive to seek and to adopt a new mode of production.

It is also possible that a successful political argument can increase state support of biological control. The tendency for increased regulation and for increased downward pressure on farm profits can be used to justify such subsidies. The state can aid biological control research through increased funds for research and for education. The research community will be well attuned to the needs for research, but the educational dimension should be broadly conceived. Programs to train pest control scientists and practitioners should be enhanced; and a broader audience in environmental studies, economics, and public affairs should be addressed. Moreover, educational needs include nonformal situations such as extension education and the media as well as the traditional classroom activities.

Subsidies for biological control technology should also be considered. Research and education to farmers are the easiest subsidies to provide, but it is more difficult to subsidize operating expenses. Heterogeneity in farm operations due to geographic and social factors makes direct operating subsidies extremely difficult to conceive and implement in a just way. Subsidies could be directed somewhat more easily toward industries producing commercial biological control agents, which would be of assistance to schemes based on augmentative biological control. Such subsidies might take the form of tax credits or other incentives to alleviate the start-up and operating expenses of such ventures.

Pricing trends and regulatory policies thus provide opportunities for research in biological control. For example, theoretical studies suggest that incentive payments to farmers or taxes on pesticides both could promote the use of IPM or other non-chemical pest control ( Cooper & Keim, 1996 ; Underwood & Caputo, 1996 ). Large farms, however, may be more sensitive than small farms to loss of profits from restrictions on pesticide use ( Whittaker et al., 1995 ). Multiple factors, however, make it hard to dislodge chemical control from its role as the dominant technology for pest control ( Cowan & Gunby, 1996 ). Organic, sustainable plant and animal crop production in the U.S. is now a $3 billion industry and growing.


We are grateful to the following people for reading a draft of this chapter in manuscript form: Paul R. Butler, Gordon R. Conway, Jack R. Coulson, David J. Girling, David J. Greathead, Carl B. Huffaker, John Mumford, Ralph Murphy, G. A. Norton, Robert Sluss, Edward Smith, and Jeffery K. Waage. We did not accept all their suggestions, but we are deeply indebted to them for stimulating further discussion. The manuscript was much improved with their help, but we remain responsible for any shortcomings it may have.

Special thanks go to the library and publications staff of the CAB International Institute of Entomology; the library staff of the Evergreen State College, particularly to C. J. Hamilton, Kate Howard, Theresa Kewell, Ernestine Kimbro, Sara Rideout, and Andrea Winship; the Division of Biological Control, University of California, Berkeley; W. G. Voigt for graphic illustrations; and D. DeMars for manuscript preparation. Ann Vandeman, Assistant Director for Management, Economic Research Service, USDA, generously helped us locate several recent studies on biological control and IPM.

Financial support from The Evergreen State College and the National Science Foundation (NSF SES-8608372) made part of the work for this chapter possible and is gratefully acknowledged.

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