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This chapter focuses on the application of biological control in support of conservation programs. It first examines the history, theory, application, benefits, and risks of biological control. It then identifies non-traditional pest targets of conservation importance suitable for biological control. Finally, it discusses novel biological control techniques and experimental approaches in conservation biology.

This chapter gives a history of organic farming and the biological technologies that organic farmers rely upon. Based on present trends, consumer demand and organic-based research are likely to increase. This raises the question of whether GE varieties can help forge a future sustainable agriculture.

This chapter deals with the more applied aspects of the Allee effect. It starts by considering the role and impact of Allee effects in the conservation of rare and endangered populations, including their interaction with habitat fragmentation and reserve design, (re)introductions, ex-situ conservation, and conservation target setting. It then considers Allee effects in the context of population management, including the management of exploited populations (fisheries, the economics of value and rarity), and pest outbreaks and eradication. It reviews methods that managers and conservationists might use for evaluating Allee effects in a population, including scientifically rigorous techniques for demonstrating their presence and calculating the Allee threshold, but also more general precautionary-type strategies for assessing the probability of Allee effects being present. The chapter ends by summarizing key points as a sort of Allee effect aide-mémoire for endangered species and conservation management.

Biocontrol can be a useful tool in forest pest management. Using insect predators, parasitoids and disease-causing pathogens as examples, this chapter discusses the different methods of biocontrol. The augmentation and conservation of natural enemies is illustrated by case studies of the inoculative release of fungal pathogens against gypsy moth, and the inundative release of egg parasitoids against spruce budworm. In classical biocontrol, the selection of appropriate natural enemies is discussed under the topics of evaluation of the pest in the target region, exploration in the pest area of origin, selection of appropriate natural enemies, quarantine and rearing, release of one or more species, and evaluation and monitoring. The risk to non-target populations is considered in relation to the use of generalist natural enemies. Classical biocontrol is illustrated by two case studies: the release of parasitoids against larch casebearer and the role of parasitoids and predators in biocontrol of winter moth. The economic benefits of biocontrol are briefly discussed.

This chapter evaluates the efficiency of experimental techniques in reducing invasive plant species in California grassland ecosystems. It discusses native plant restoration approaches, focusing on techniques to tip the competitive balance toward native species and away from exotic species. These techniques include the reduction of soil nitrogen availability, livestock grazing, prescribed burning, herbicide application, and biological control.

The traditional view of weasels as ruthless predators capable of holding down the numbers of pest rodents tends to underestimate the rate at which pest populations can replace the individuals killed. In fact, weasels can exterminate rodents only in a small area where they have no prey choice and no escape. Contrariwise, shooting of game birds is a widespread sport in North America, Britain, and Europe, and concern to maximize the productivity of game bird nesting seasons often includes control of nest predators, including stoats and weasels. By protecting nesting game- and song-birds from temporary damage by weasels, game estates in the UK also play a valuable conservation role which benefits many other species that would otherwise get no protection at all from their main enemy, chemical-based agriculture. Weasels are abundant and resilient, so are seldom included in any conservation legislation, but they do need protection from cruel traps and secondary poisoning.

This chapter discusses the major role of Lepidoptera populations in natural and human communities. Lepidoptera larvae damage agricultural crops and are a major problem in stored meal, grain, nuts, and in woolen products. Conversely, they play significant roles in pollination in natural communities and aid in crop pollination. Caterpillars convert complex chemical energy in plants to digestible food for other members of the food chain. Lepidoptera are also decomposers, assisting in reducing fallen leaves and fruit, fungi, and animal products to humus. Several species are also introduced as biological control agents.

Once established, some introduced species experience increased fitness or demographic rates in their introduced range compared to their native range. The phenomenon of species becoming invasive as a result of increased success is referred to as “invasion success.” The enemy release hypothesis (ERH) is a leading hypothesis of invasion success; it posits that introduced species lose enemies and undergo release from enemy control. The ERH provides the underpinnings for the management practice of biological control; if enemy release is important, then re-establishing the link between introduced species and natural enemies could provide an effective means of control. Despite the popularity of the ERH as an explanation for invasion success and its implications for biological control, our review reveals that it has only been properly evaluated in limited contexts. More rigorous tests of the ERH are needed for invasive species in higher trophic levels and in aquatic systems to reveal the general importance of this hypothesis of invasion success. A fundamental understanding of what causes invasion success is essential to apply effective control strategies for the management of invasive species.

This chapter focuses on the history and impact of tamarisk biological control in the form of defoliation by Diorhabda spp. leaf beetles. The beetles have become controversial despite their spectacular success as biological control agents. The chapter first presents a brief history of weed biological control before turning to the selection of tamarisk as a biocontrol target and the leaf beetle as biocontrol agent. It then examines the biology of leaf beetles, including their taxonomy and phenology, in order to have a better understanding of their current and future impact on riparian ecosystems as well as their use as a tamarisk management tool. It also considers how beetles congregate to defoliate tamarisk and concludes by discussing the long-term outlook for Diorhabda in tamarisk control.

In its early history, the US National Park Service (NPS) had no policy on nonnative species, and even introduced nonnative fishes for sport fishing and plants for landscaping. By the 1920s, scientists within and outside the NPS militated against new introductions and urged the agency to minimize or eradicate existing ones, but not until a 1968 directive was such a policy substantially implemented. Some park efforts to eradicate or decrease mammal populations aroused opposition from hunters or advocates of animal rights. Park Science was first published in 1980 and initially targeted NPS managers; in the 1990s it broadened its audience to include the general public. Articles in Park Science, though more heavily focused on management than those in most academic journals, track most of the explosive recent development of invasion biology, in particular incorporating the recognition that some invasions can affect entire ecosystems rather than just particular native species. The journal has generally downplayed controversies that have recently roiled invasion biology. National parks, islands in a larger landscape and unable to control national policy on nonnative species, are continually invaded by new nonnatives, but the NPS has risen to the challenge of managing them with some striking successes.

Data obtained from studies of various topics in ant–plant interactions could potentially be applied in insect pest management programs of agricultural systems. Ants possess many characteristics that are associated with the potential to act as biological control agents, especially in tropical agroecosystems, and an economically beneficial role has been associated with ants used for such purposes. Nevertheless, the positive effects of several ant attributes (for example, predation of herbivores, pollination, soil improvement, and nutrient cycling) must be weighed against possible disadvantages (such as leaf-cutter ants and seed predators). Some ants feed on or disturb plants, act as vectors of plant diseases, benefit damaging Hemiptera, and may attack humans, domestic animals, or other beneficial animals. In short, virtually all ant species that prey on pests also possess some potential disadvantages. This chapter reviews some general characteristics of agricultural systems, the herbivore–ant relationship, the role of ants as biological control agents (describing two case studies: maize and coffee), and the relationship between biological control and the study of interspecific interactions.

This chapter demonstrates the use of experimental approaches to control or eliminate exotic and invasive species. It provides an overview of case studies that employ traditional techniques of experimental design to gather information on both invading and indigenous species and form solutions to the invasion problem. It highlights several aspects of integrated pest management (IPM) approaches, the integration and application of multiple control methods, and the correct application of biological control.

This chapter assesses biological control strategies that can reduce turfgrass insect pest populations. Biological control refers to the suppression of pest populations through the activity of living organisms or their by-products. Although a majority of this book is devoted to understanding turfgrass pests, most organisms associated with turfgrass are not pests but instead may be considered beneficial because they reduce thatch, help recycle soil nutrients, or are natural enemies of pest species. Pest outbreaks can sometimes be traced to the absence of natural control agents in the turf environment. Vertebrate and invertebrate predators, insect parasitoids, and microbial pathogens may act as natural enemies of turfgrass pests. Although the effect of one species of natural enemy may be minor, the combined effects of predators, parasitoids, and pathogens can cause considerable reductions in pest populations. Additional agents can be considered as biological controls. These include fungal endophytes (which confer host-plant resistance to some insects), botanicals (botanically derived insecticides), and synthetic compounds that mimic the activity of insect-produced compounds, such as growth hormones and pheromones.

This chapter focuses on mechanistic theoretical approaches to explain the emergence of ratio dependence at a global scale from various behavioral models of species interaction. It explains how refuges and spatial heterogeneity as well as forms of temporal and biological heterogeneities can lead to a ratio-dependent functional response. It provides a two-patch model that shows by what method donor control can emerge from being a prey refuge and being subject to intense predation. It also discusses how ratio dependence emerges in realistic models of predator-prey interactions where spatial distribution of both the predator and prey is explicitly followed. It highlights application of these models to the explanation of successful biological control of insect pests.

Human modification of the landscape can increase the transmission of schistosomiasis, a snail-borne parasitic infection prevalent in Sub-Saharan Africa. The construction of dams and irrigation schemes increases the habitat available for the freshwater snails that serve as the parasite’s intermediate host. Schistosomiasis is considered both a cause and consequence of poverty. The disease is treatable, but its persistence in the environment makes it difficult to prevent reinfection after treatment. Interventions that address the environmental source of infection are a necessary complement to mass treatment campaigns. We present a promising ecological solution for schistosomiasis control that harnesses predator-prey dynamics to suppress snail populations and parasite transmission. We present data on the ecological and epidemiological impacts of restoring Macrobrachium vollenhovenii, a freshwater prawn native to the Senegal River. Harnessing ecology to control disease transmission may be a viable strategy in other geographic regions and other disease systems.

The restoration of California's wildflower flora will require management strategies involving the entire landscape, with a historical perspective to be kept in mind. Local research studies have restricted application because local, high-precision field measurements with limited time scales of data collection have often lead to dangers of extrapolation to landscapes. It is important to increase the breadth of data collection in order to see the big picture of landscapes over long time scales. Another approach is to employ an “adaptive management” perspective. Potential avenues for effective management and conservation to preserve some degree of history in the landscape include spring burning, the use of pathogens as biological controls of invasives, the dedication of new wildflower reserves, and the encouragement of seasonal grazing by domesticated livestock.