Defining and Implementing Ecologically Based Pest Management
There is a need to develop new pest-management systems that are long-term, cost-effective, solve unmet needs, and protect human and environmental health. As presented in Chapter 1, conventional, chemically based pest-management strategies encourage short-term solutions that can be harmful to the environment and to human health. Broad-spectrum chemicals also are ineffective against some pest problems. Future pest-management systems will be based on a broad knowledge of the agroecosystem and will seek to manage rather than eliminate pests. Agricultural practices that augment natural processes that suppress pests, where available, will replace existing practices that disrupt natural processes; and these practices will be supplemented with the judicious use of biological-control organisms and products, target-specific chemical pesticides, and pest-resistant plants. It will also be necessary to reopen and develop channels of communication at all levels that increase the flow of information and cooperative action, subsequently lowering risk to users, fostering interdisciplinary interaction, and improving the profitability of alternative pest-control methods.
GOALS OF ECOLOGICALLY BASED PEST MANAGEMENT
The fundamental goals of EBPM are (1) safety, (2) profitability, and (3) durability.
Pest-management systems must be safe for growers and workers who use them, and for consumers of the food produced. Minimizing health risks must be a primary criterion of acceptability of novel management systems.
Pest control strategies must be cost-effective as well as effective, easy to implement, and readily integrated with other crop-production practices. Economic factors involving cost-effectiveness include crop prices, costs and availability of labor, land, equipment, and other production inputs.
Pest-management programs must ensure that pests in the agroecosystem can be managed over the long-term without adverse environmental, economic, or safety consequences. Current pest-management strategies that rely on repeated applications of conventional broad-spectrum pesticides encourage the development of resistant species. In new ecologically based approaches, addressing potential development of pest resistance will be important.
EBPM promotes the economic and environmental viability of agriculture by using knowledge of interactions between crops, pests, and naturally occurring pest-control organisms to modify cropping systems in ways that reduce damage associated with pests. Ecologically based management relies on a comprehensive knowledge of the ecosystem, including the natural biological interactions that suppress pest populations. It is based on the recognition that many conventional agricultural practices disrupt natural processes that suppress pests. Agricultural practices recommended by EBPM will augment natural processes, supplemented by biological-control organisms and products, resistant plants, and targeted pesticides.
An ecosystem is dynamic with interacting physical, chemical, and biological processes. The coexisting crops, herbivores, predators, pathogens, weeds, and other organisms interact with one another and respond to their environment. Each organism has developed a repertoire of offensive and defensive maneuvers in response to changes in the behavior of other organisms in the cropping system. This web of interrelated interactions also confers stability on the system; while a population increases and decreases, it is subject to the checks and balances imposed by populations of the other organisms.
Stability (i.e., low variance in density of pests over time) is an essential feature of successful pest management. When effective predators, parasites, pathogens, or competitors of potentially destructive pests are present in the managed ecosystem, pest populations are suppressed and held in check. In natural systems, biological-control organisms are often quite diverse, leading to stable, low pest populations.
Activity of most biological organisms is density dependent—i.e., when pest density is low, density of, and hence suppressive activity of control organisms tends to be low, and vice versa. Negative feedback related to population density keeps both pest and control organism from both glut and extinction. Because neither pesticides nor host-plant resistance methods are responsive to feedback, achieving stability and balance within the agroecosystem is not possible with those systems, but is a fundamental goal of EBPM. EBPM is founded on the importance of natural processes inherent within agricultural and forest produc-
tion systems. To this is added, in a complementary way, other technologies for managing pest problems.
Ecological balance is more difficult to attain in a highly modified agricultural environment, such as a large-scale monoculture farm, where the goal is to maximize production of one crop species exclusively. In this monoculture ecosystem, biological-control organisms that depend on other plant species for growth and reproduction may suffer tremendous population reductions. On the other hand, a pest adapted to utilizing the primary crop has an unlimited resource at hand, resulting in a pest population explosion.
The National Research Council report on alternative agriculture describes alternative systems to manage pests, crop nutrients, soil erosion, and livestock production (National Research Council, 1989b). The goal of alternative agriculture—profitable, safe, and healthy ecosystems achieved by integrating individual practices into an overall farm management system—are consistent with the goals of EBPM.
EBPM should be viewed in the context of whole-farming systems. Pest-management methods cannot be isolated from other components of agronomic systems such as fertilization, cultivation, cropping patterns, and farm economics (National Research Council, 1989b, 1991). These physical, biological, and chemical practices are interrelated; changing one system component will impact another entity. For example, choosing a particular rotating crop can augment suppression of soil-borne plant pathogens and affect levels of soil nitrogen. Such natural processes of interdependence are augmented and exploited by ecologically based pest-management systems. Biological and ecological processes are fundamental to pest control even in the most intensively managed ecosystems; EBPM builds on and supplements them, rather than impeding or replacing them.
SUPPLEMENTS TO NATURAL PROCESSES
A major premise of EBPM is that most potential pest species are held in check by naturally occurring beneficial organisms. Supplemental inputs, either natural or synthetic, must not suppress either the populations or activities of these indigenous beneficial organisms. It is therefore essential that the use of supplemental inputs be based on an understanding of target organisms so that the potential for development of resistance, disruption of natural and biological processes of control, and unintended effects on nontarget organisms or ecosystems are minimized. Supplemental inputs that meet the criteria of safety, profitability, and durability are valuable and, quite possibly, finite resources. Their use should be accompanied by sophisticated diagnostic and monitoring tools and methods of deployment that prolong their effect. Lasting solutions require anticipation of potential disruptions and evolutionary responses that could result from pest-management practices (Gould, 1991).
The self-sustaining system requires no supplemental inputs, relying instead
Integrating Components of a Managed Ecosystem: Cover Crops
Cover crops are an excellent example of an innovative strategy to integrate multiple components of a managed ecosystem. These noncrop plant species, such as vetch and clover, are grown as ground cover to manage pests, provide nitrogen for subsequent crops, increase soil organic matter, and reduce soil erosion (National Research Council, 1989b). Because cover crops increase ecosystem biodiversity which, in turn, affects multiple biological interactions involving pest management, soil fertility, and plant nutrition, ecosystem interactions should be carefully considered when integrating a cover crop into a pest-management strategy. Since the long-term impacts of cover crops are not well known, additional research can provide a greater understanding of their role in crop production (Hanna et al., 1995).
Cover crops can provide habitat and a food source for biological-control organisms. California vineyard managers plant clover and other legume ground covers to attract beneficial wasps and spiders; their abundance is associated with decreases in leafhopper pests (Hanna et al., 1995; National Research Council, 1989a). Some cover crops produce allelopathic compounds that can suppress plant parasitic nematodes. Ground covers also can delay weed emergence, giving a competitive edge to the primary crop.
However, interactions of a cover crop with other ecosystem components can lead to undesirable effects; a cover crop species that is optimal for biological control of arthropod pests may not be competitive with a troublesome weed (Ingels, 1995). Thus, considerable knowledge of ecosystem processes is necessary to successfully manage pests in cover-cropping systems.
Soil Fertility and Plant Nutrition
Cover crops can increase soil fertility and plant nutrition; legumes such as vetch and clovers exhibit powerful nitrogen-supplying capabilities. Symbiotic bacteria initiate nodules on the roots of legumes, which transform atmospheric nitrogen into a useful nitrogen source for plant growth (nitrogen fixation). This complex nitrogen-transformation process is influenced by numerous factors including soil microorganisms, cover crop species, tillage, and water (National Research Council, 1989b).
Since cover crops may also remove nutrients from the soil, nutrient status of a primary crop needs to be monitored. Thus, growers need to weigh the benefits and disadvantages of using cover crops to increase soil fertility and plant nutrition.
on natural, biological processes. Supplemental inputs will undoubtedly be required, however, to achieve EBPM. These will include biological-control organisms and products, narrow-spectrum synthetic pesticides, and resistant plants.
Biological-control organisms are living organisms that can be used to manage arthropod (mites and insects), weed, and plant (bacteria, fungi, viruses, and nematodes) pests and pathogens. Generally, control organisms do not immediately alleviate disease or prevent or curtail attack; they also do not immediately reduce the pest population. Rather, control is generally achieved over a period of several generations. Biological control organisms commonly interacting with their hosts at low population densities, preventing pests from reproducing to economically important population levels. Control organisms are themselves arthropods, plants, and pathogens and are as diverse as the pests (Ferris, 1992; Flint, 1992; Schroth et al., 1992; Turner, 1992):
arthropods that prey on or parasitize other arthropods,
arthropods that prey on or parasitize plants,
pathogens of plant pests,
bacterial or fungal antagonists of plant pathogens,
beneficial nematodes that parasitize arthropods,
mild strains of plant pathogens, and
other beneficial organisms that parasitize or prey on plant pathogens or nematodes.
Predatory arthropods can be very host specific, depending on their ability to locate, consume, and utilize a particular prey species for growth and reproduction; however, environmental factors and habitat may modify prey specificity. A predator invariably consumes more than one individual during its life span and, if conditions are favorable, some arthropod organisms kill hundreds of host individuals during their development. Arthropod parasitoids attack and disarm the arthropod host species and subsequently deposit one or more eggs within or on the host organism. Parasitoid larvae then feed on and complete development on a host individual, and in the process, kill the host. Parasitic organisms are usually highly host and habitat specific. Arthropod herbivores that prefer feeding on weed plants can be used as controls, feeding on foliage, roots, stems, flowers, fruit, or seeds of weeds.
Viruses, bacteria, fungi, protozoa, and other microbes that cause disease in arthropods, plant pathogens, or weeds are also used as biological-control organisms. Under favorable conditions, they infect their hosts and can cause epidemics that can lead to a marked decline in the pest population. Certain of these persist on the plant, in the pest, or in the environment, causing recurring infections in their hosts.
Microbial antagonists can suppress plant pathogens by producing antibiotics or by means of competition—producing larger populations, and thus occupying and competing for the same ecological niche. A competitor will challenge the pathogen for infection sites, nourishment, or other resources and, in the process, reduce the population size of the plant pathogen. Microbial antagonists can produce toxins active against arthropods, plant pathogens, or weeds, or compete with plant pathogens for nutrients or preferred sites on plant surfaces. Mild strains of plant pathogens that cause little or no disease can induce resistance responses in the plant or otherwise provide protection from disease.
Genes or gene products derived from living organisms that kill, disable, or otherwise regulate the behavior of plant pests are biological-control products. Examples include the Bacillus thuringiensis (Bt) toxin, delivered by a killed microbe, and pheromones or other semiochemicals used to kill or disrupt the reproduction of arthropod pests.
It must be noted that genes or gene products are derived from living organisms, but they are not inherently more suitable supplements than synthetic products. Indeed, certain synthetic products can be less detrimental to environmental balances than some products derived from organisms; some natural plant products used to formulate botanical insecticides such as rotenone and pyrethrum have broad-spectrum activity and can be highly toxic to beneficial organisms. It is the spectrum and activity of products used in ecologically based pest management that are of primary importance rather than the source of the products. The most useful biological-control products are those that have minimal impact on all components of the agroecosystem—except for the target pest.
Narrow-spectrum synthetic pesticides that meet the criteria of safety, profitability, and durability are suitable supplements for EBPM. For example, the synthetic insecticide pirimicarb is highly selective for one group of pest arthropods, aphids, and does not adversely affect most biological-control organisms.
Plants that have developed resistance against pests will be important components of EBPM. Plant breeders have successfully identified and deployed genes for disease and arthropod resistance in numerous crops; in the future, molecular genetic methods will become more important as a means to producing pest-resistant plants. At present, resistance is the predominant defense against many plant diseases, such as rust diseases, that would otherwise severely limit cereal
Pirimicarb: The Saga of a Selective Pesticide
The insecticide pirimicarb is a selective aphicide; it controls many of the most damaging aphid pests but has little if any effect on most other arthropods. Because it does not directly interfere with beneficial predatory and parasitic arthropods, it fits well in alternative pest-management programs that rely on biological control. However, pirimicarb had a relatively short early history in the United States; it was first registered in 1974 but was voluntarily withdrawn from the market in 1981 because of regulatory and marketing problems.
Pirimicarb was registered only on specialty crops, specifically potato and greenhouse crops, where aphids are serious pests. After initial registration, the Environmental Protection Agency (EPA) requested additional metabolism and residue information that would have been very expensive to gather. Also during this time, the synthetic pyrethroid insecticides were coming on the market, and many pest managers preferred products such as these that had broad-spectrum activity. Faced with the economics of clearing regulatory hurdles as well as facing competition from the new pyrethroids, it was decided to withdraw registration of pirimicarb in the United States, even though the product continued to be used in Canada and Europe.
Over the past 20 years, the climate in the United States has improved to favor the use of selective products that provide effective and economic alternatives to more broad-spectrum pesticides. Pirimicarb is currently undergoing reregistration review in Europe. Data required for this review will satisfy some of the EPA requirements; therefore the parent company intends to once again submit pirimicarb for registration in the United States.
Had a mechanism been in place in the 1970s to foster the development of specific pesticides by helping companies meet regulatory requirements, pirimicarb and other selective pesticides would likely be more widely used in agriculture today.
SOURCE: Personal communication, 1995, M. Moss, ZENECA Ag Products, Wilmington, Delaware.
crop production in much of the world. In the case of rust diseases, a plant cultivar generally is resistant to only one specific race of a pathogen. Other races of the pathogen can infect the plant, and the shift in race composition of the pathogen leads to a boom-and-bust syndrome of rust diseases. Strategies of resistance-gene deployment, in which fields are planted with mixtures of cultivars, each with a different race-specific resistance gene or with one cultivar containing multiple race-specific resistance genes, can be very successful in diminishing this syndrome. Race-specific resistance genes deployed in this manner can be quite successful in controlling plant diseases. Plants also may have a general resistance to plant pests, conferred by the collective action of multiple genes. Polygenic
resistance can be quite stable and for this reason will be an important component of EBPM.
To date, resistant plants have been developed almost entirely through plant breeding. Future breeding programs will continue to rely on diverse wild germplasm as a source of resistance genes but will also incorporate resistance genes identified in research programs. These investigations will enhance the plant's inherent strength to survive in its environment. There is good reason to believe, based on the tremendous recent progress in identifying pest-resistance genes, that numerous genes identified by these approaches will be incorporated into crop plants in the future. The promise of durable resistance can only be reached, however, if breeding programs also strive to enhance, rather than diminish, the genetic diversity of plants grown in forest or agricultural ecosystems. Stable and long-lasting pest management will depend on the availability of crop plants with broad bases of genetic variability.
ECONOMIC FEASIBILITY OF ECOLOGICALLY BASED PEST MANAGEMENT
EBPM will be implemented on a farm level and must be profitable for the grower. Adoption of an alternative pest-management strategy depends on its relative profitability, risk, public policies, and the information and education available to the grower. The realistic potential of EBPM systems will, in large part, depend on how feasible those systems appear to the individuals who must implement the systems. Management systems that effectively suppress pest populations but suffer from poor profits, high risks, discouragement by public policy, or lack of available information for the grower will not be implemented.
The economic feasibility of pest management must be determined by examining the economic factors a grower might consider when considering adoption of EBPM strategies. It should be noted that a larger knowledge base is necessary to make economic comparisons of EBPM strategies.
Economic Feasibility of Pest Management
Economic feasibility, as defined by Reichelderfer (1981), refers to the likelihood that a management system will bring net returns greater or equal to that of any other management system being considered by a grower. A grower will be encouraged to adopt an ecologically based technology if it results in net profit at least as great as does the system the grower is currently using. Relative profit is a great incentive to adoption. Indeed, if the profit margin is great enough, growers may even be induced to alter their management styles in order to take advantage of the new opportunity.
Economic feasibility does not consider social costs and benefits, but it is the starting point for broader analysis of the desirability of a pest-management sys-
Biological Control of Citrus Pests
Worldwide, efforts to develop ecologically based approaches to arthropod, pathogen, and weed control for citrus production are producing diverse, effective, and economical alternatives to frequent, heavy applications of pesticides. Some of the methods noted below are well established, some are being rediscovered, and others are still in developmental stages.
Biological Control of Arthropods
Augmentation of Existing Control Organisms
In California, the California red scale (Aonidiella aurantii), one of the primary citrus pests, is now controlled by augmenting populations of Aphytis lingnanensis—a parasitoid of the red scale. Normally A. lingnanensis is more abundant in the summer, whereas adult female red scales accumulate in the spring. The control method is to release the parasitoid, commercially raised in grower-owned cooperatives, in the spring when the adult female red scale appears. The parasitoid is active against the female red scale before it can reproduce, thus eliminating the need for multiple applications of broad-spectrum scalicides (Graebner et al., 1984).
Commercially produced microbial pesticides that have been investigated for use in the citrus system include the fungus Hirsutella thompsonii, which is active against the citrus rust mite Phyllocoptruta oleivora, the most important citrus pest worldwide. Although problems with formulation of this product (Mycar®) limited the availability of this fungus in the 1980s, researchers continue to seek methods to solve these difficulties (McCoy and Couch, 1982). A commercial product currently in use for biological control of root weevils in Florida citrus is the entomophagous nematode Steinernema riobravis. This beneficial, soil-inhabiting nematode is cosmopolitan in distribution, but occurs naturally in soils at low levels, insufficient for effective management of the weevil larvae and pupae. Commercial fermentation culture has led to the marketing of a product (Biovector®) that is applied to the soil beneath citrus trees. The degree of success with this biological-control product remains to be determined, as the product has been in use for only 3 years (McCoy and Duncan, 1995). An acaricide (miticide) recently registered for use in citrus, Avermectin®, interferes with molting and transformation of mites from nymphs to adults. This growth regulator is an example of biologically based products that can be employed in pest management (Knapp, 1995).
Conservation of Existing Control Organisms
The importance of already existing natural processes of control is illustrated by the example of the bayberry whitefly, Parabemisia myricae, an introduced pest from Japan that became established in California citrus groves. Parasitoids of the whitefly were found in Japan, and several species were introduced into California, but without successful control. However, in 1982 populations of the whitefly declined
dramatically. It soon became apparent that a native parasitoid Eretmocerus debachi had begun to attack the bayberry whitefly and eventually reduced it from a serious pest to simply another of the many innocuous species that inhabit citrus groves.
Classical Biological Control
The most famous use of an exotic biological-control organism to achieve permanent control of an arthropod pest of exotic origin is the control of the cottony-cushion scale, Icerya purchasi, that threatened the continued existence of the California citrus industry in the late 1800s. The predaceous Vedalia beetle, Rodolia cardinalis, was introduced into California citrus groves in 1889. By 1890, the cottony-cushion scale was no longer a threat to California citrus production (DeBach and Rosen, 1991). This success in California led to similar successful introductions of the Vedalia beetle into citrus groves in Florida, Texas, and eventually worldwide in 25 other countries (DeBach, 1974).
Biological Control of Plant Disease
Cross-Protection against Citrus Tristeza
Cross-protection against citrus tristeza virus has been used for more than 2 decades in Brazil, where millions of citrus trees have been protected against highly virulent strains of the virus by mild strains (Costa and Müller, 1980). The citrus tristeza virus is a serious disease organism that has crippled commercial industries worldwide. Transmitted by aphid vectors, citrus tristeza virus has escaped attempts at management through aphid control, disease therapy, and continued efforts to develop effective host-plant resistance. Inoculation of healthy susceptible trees with a harmless ''mild strain" of the virus has been demonstrated to confer protection against subsequent inoculation with more virulent strains.
Suppression of Postharvest Rot
Early in 1995, two microorganisms were registered by the Environmental Protection Agency for the biological control of postharvest diseases of citrus. The yeast Candida oliophila was registered for control of postharvest rot of citrus and apple, and the bacterium Pseudomonas syringae was registered for control of storage rots of citrus, apple, and pear (Wilson and Janisiewicz, 1995).
Biological Control of Weeds
A host-specific strain of the pathogenic fungus Phytophthora palmivora has been developed as the commercial mycoherbicide DeVine® to manage milkweed vine (Morrenia odorata), which infests citrus groves.
tem (Headly, 1985; Reichelderfer, 1985). Reichelderfer (1981) and Carlson (1988) identified several factors which determine economic feasibility. These factors can be grouped either as pest control factors or economic factors. The interrelationships between these two factors indicate how difficult it is to achieve economic feasibility, and the need for biological and social scientists to cooperate in research, development, and distribution of ecologically based management systems (Headly, 1985; Reichelderfer, 1981).
Three pest-control factors that have important effects on the economic feasibility of a pest-management system are (1) the severity of pest-induced losses, (2) the variability of pest populations, and (3) the technical efficacy of the management system. These factors are defined in the discussion below.
A pest-management approach is economically feasible only if it reduces an important pest population to an extent that it no longer limits profitability. If even low population densities of the pest can cause serious damage, economic losses may remain too high after the management system is implemented and the relative economic benefits from the management system will decrease (Carlson, 1988; Reichelderfer, 1981). Hence, the economic feasibility of an ecologically based pest-management system will depend on how much damage the steady-state population of the pest can cause. Economically feasible, ecologically based control may be easier to effect for pests that can be tolerated at moderate populations without economic damage.
The variability of the pest population over time and space can also affect economic feasibility of a management system. If the pest is only a problem every few years, then an economically rational decision would be to wait until the pest surpassed an economic threshold before treating it. Waiting to employ a biological-control organism until the pest problem becomes severe, however, may not be feasible for all biological-control organisms and depends on their method of deployment. Inoculating the crop to prevent a pest problem that occurs only infrequently will result in unnecessary expenses in some or perhaps most years. In cases where the pest problem occurs frequently and predictably, routine inoculation with biological-control organisms may be economically feasible (Carlson, 1988; Reichelderfer, 1981). In contrast, some augmentative or classical biological control can provide permanent population reduction below economic levels, i.e., prevent the pest from becoming a pest. This is an advantage in many cases—classical biological control using organisms is preventative rather than therapeutic.
Technical efficacy of an ecologically based management system refers to the ability of the system to prevent or reduce damage caused by pest populations. As the management system becomes more efficacious, it becomes more economically feasible, assuming there is no change in other factors such as the cost of
other production inputs, the prices of commodities, or the effectiveness of alternative management systems (Reichelderfer, 1981).
Economic factors such as crop price and yield, costs of alternate management methods, and implementation costs determine the economic return a grower realizes from use of an alternative pest control system.
Crop price and yield determine the gross return a grower receives per hectare. As the gross return goes up, so does the value per unit of pest damage, which in turn increases the value of management systems that decrease the damage (Carlson, 1988; Reichelderfer, 1981). Crops that produce large gross returns per hectare create strong incentives to invest in pest-management systems. Growers will, in general, be more willing to invest in alternative pest control systems when the value per hectare of the crop they are producing is large. Ecologically based management systems that solve pest problems that cannot be solved with current systems will be immediately attractive to growers, particularly if the cost of current pest damage is high.
New, ecologically based management strategies will compete for adoption and implementation with the systems currently used by growers. In most cases, the current system is based on the use of broad-spectrum, conventional pesticides to kill pests. The costs of an alternative management system include the costs of (1) pesticide, biological-control organism, biological-control product, or other supplemental input, (2) capital investment of machinery, (3) machinery operation, (4) management time, and (5) labor (Carlson, 1988).
Some ecologically based methods are much cheaper than current systems. Reichelderfer (1981) and Cate and Hinkle (1993) for example, noted the cost advantages of classical biological-control methods over pesticides. The benefits of permanent, successful pest management achieved with a one-time introduction of a biological-control organism will, over time, be more cost-effective than annual pesticide applications. Costs of seasonal releases of a biological-control organism may be competitive with pesticidal alternatives (Reichelderfer, 1985).
Implementation costs are the costs imposed by switching to and learning a new management system. These costs also include the time and money the grower must invest in physical and human capital to be able to use the new management system. Switching to a new system may require training or the purchase of equipment and retirement of current equipment. Initially, more labor and presumably more management for an indefinite time period would be required to learn and integrate the management system into the farming system. Any effects of a new pest-management system on farm program eligibility, off-farm employment, or other factors affecting income are also included in implementation costs.
Implementation costs are very important considerations for growers decid-
ing to implement alternative pest-management systems. The more similar the new management system is to the current system, the less likely new machinery will be needed, and the easier it will be to learn the new system—all resulting in low implementation costs. Biological-control organisms formulated as seed treatments, for example, may be readily integrated into current agricultural practices and require no specialized equipment for implementation.
Plant breeding for arthropod and disease resistance is an excellent example of an ecologically based approach that has been easily integrated into current production systems. Growers regularly substitute one resistant variety for another with very low implementation costs. Indeed, the ongoing development of new resistant varieties is the primary line of defense against important plant diseases such as wheat rusts that annually spread into the United States from Mexico.
The potential of ecologically based management systems may depend as much on how well they meet the economic criteria of those who use them, as on their direct effect on pest populations.
Economic Feasibility and Risk
Risk plays a large role in a grower's decision to adopt a new pest-management system. In the case of growers,
the value of controlling a pest, whose incidence varies in an uncertain way, is greater than the average loss caused to them by the pest. Risk-averse growers are willing to pay a premium or insurance charge to reduce the risk of uncertainty they face (Tisdell et al., 1984: p. 172).
In other words, growers are interested in minimizing the variability surrounding returns and yields as well as the absolute return or yield achieved (Headly, 1985).
There are tradeoffs between expected net returns and year-to-year variability of returns (Kramer et al., 1983; Reichelderfer, 1981). Kramer et al. (1983) found that profit maximization and risk aversion were the most important criteria determining the choice of soil conservation technologies. Even when required to meet reduction standards, risk-averse growers chose the more erosive systems to guarantee less net return variability; risk-neutral growers adopted more practices optimizing soil conservation.
Growers have been quick to adopt pesticides because of the certainty pesticides bring to production and profitability, and increased uncertainty about pest damage results in increased use of pesticides. Too much variability in net returns from year to year may induce a risk-averse grower to select a pest-management system that produces more certain results even if average returns are lower (Headly, 1985; Tisdell et al., 1984). Risk-averse growers with tight cash flows may decide to use a production system that brings a lower average return but has less income variability than a production system that is more variable but has a
higher average return. This also could speak to technology systems where the returns over the life of the investment are high but initial returns are low.
Uncertainty about the efficacy of ecologically based management systems is a major source of concern for growers. Uncertainty surrounding the effectiveness and consistency of alternative pest-management systems has been a barrier to the adoption of IPM practices. Fernandez-Cornejo et al. (1992), for example, found that adopters of IPM technologies were less risk-averse than those who did not adopt IPM. Risk-averse growers were more likely to rely on a conventional pesticide system (Fernandez-Cornejo et al., 1992) and placed more value on immediate reduction of the pest (Reichelderfer, 1985). Risk averse growers may be reluctant to forgo application of a pesticide while waiting for uncertain results from an ecologically based system.
Risk also depends on the stability and supply of the biological-control organisms, biological-control products, or other supplemental inputs to ecologically based systems. A steady supply of biological-control organisms or other inputs to the system or knowledge is essential to insure that growers can find what they need, when they need it. Though supply shortages can also occur in conventional pest-management systems, uncertainty about the availability or use of an essential component of an ecologically based system increases the risk to the grower of using that system.
The interaction of economic feasibility and risk largely determines the likelihood that an ecologically based management system will be adopted or implemented by growers. Economic feasibility and risk can create both barriers to or opportunities for the implementation of ecologically based management systems. A national initiative to develop and implement ecologically based systems should focus on those strategic opportunities where the economic feasibility and risk characteristics increase the likelihood of eventual adoption and implementation by growers.
Safety, profitability, and durability are not mutually exclusive, but the public interest in reducing risk to human and environmental health may outweigh private considerations of economic feasibility. Directing investments toward ecologically based systems that are economically feasible and less risky for growers will help ensure that the systems are profitable and at least economically durable. Growers, however, cannot consider all the social and environmental costs of alternative management systems when they make their decisions. For instance, society needs to consider costs to monitor for potential development of resistance of EBPM solutions implemented in managed agricultural and forest ecosystems. The public at large also benefits from effective, long-term solutions to pest problems that minimize environmental and health risks. Strategic opportunities to encourage grower adoption and minimize the ecological and human health risks should also be explicitly identified as part of the planning for a national initiative to implement ecologically based management systems.
As a first step, an ecologically based management initiative should be directed to systems that initially
promise to reduce risks to human or environmental health posed by current management practices,
promise to achieve lasting solutions to pest problems,
solve pest problems that have no feasible pesticide solution,
are less expensive than conventional pesticides or are applicable to high-value crops,
require minimal changes in current production systems, and
promise to reduce the risk and variability of annual returns to the grower.
Ecologically based systems that meet one of these criteria are targets for investment of public resources; systems that meet several of these investment criteria are the most promising targets.
Growers are likely to adopt EBPM systems that generate lower risks and higher profits. There is always perceived risk in embracing new technologies; the greater the divergence from previous practices, the greater the perceived risk. The value of information is that it reduces the pest manager's uncertainty about pest control decision making (Lawson, 1982), thereby increasing the likelihood of acceptance of a new practice. The public at large has an opportunity to invest in new knowledge and tools that will help the grower successfully implement ecologically based pest-management systems.
THE ROLE OF INFORMATION IN PEST MANAGEMENT
The complexity of managed ecosystems indicates a need for more multidisciplinary information to develop and implement EBPM. All technological advances are driven by information flow; the importance of this for development and adoption of new pest-management technologies has been well documented (e.g., Edwards and Ford, 1992; Fitzner, 1993; Frisbie, 1989; Frisbie et al., 1992; Grieshop et al., 1988; Lawson, 1982; Mumford, 1982; Norton, 1982; Poston, 1989; Putter and Van der Graaff, 1989; Scott and Harris, 1989; Tette and Jacobsen, 1992; Van Driesche, 1991; van Lenteren, 1989; Zalom and Fry, 1992). Conventional pest management itself requires a high level of information, some of which is not being effectively transferred from research to the field. Hoy (1989) stated that "… ineffective transfer of information from the developmental phase to the implementation phase seems to explain why new pest-management techniques are not implemented more frequently." Ecologically based IPM will require an even higher level of knowledge to guide management decisions (Edwards and Ford, 1992; Fitzner, 1993). Grieshop et al. (1988) stated that "attributes of [an] IPM innovation, particularly its complexity, figure prominently in adoption rates." Tremendous complexity of EBPM may result in slow adoption rates. Therefore, we are faced with a dilemma; current IPM technology
Integrated Management of Frost Injury and Fire Blight
Frost injury is a serious problem on agricultural plants, most of which cannot tolerate ice formation within their tissues. Annual losses to agricultural production in the United States alone are estimated at more than $1 billion. At temperatures only slightly below freezing (-10° C and above), even frost-sensitive plants have a natural ability to super cool, thereby avoiding ice formation within their tissues. The capacity to super cool is limited, however, by the presence of ice-nucleation active (Ina+) bacteria, especially Pseudomonas syringae, a common inhabitant of aerial plant surfaces. Ina+ bacteria have an outer-membrane protein—the ice protein—that orients water molecules in an arrangement that mimics the crystalline structure of ice. The oriented water molecules do not super cool but, instead, freeze at temperatures very close to freezing (i.e., -2° C to -5° C). Once ice formation is catalyzed by Ina+ bacteria on the plant surface, ice crystals rapidly spread into the plant, injuring plant tissues irreversibly. Injury at temperatures close to freezing (i.e., -2° C to -5° C) can be avoided by reducing the number of Ina+ bacteria.
Fire blight, an important disease of pear and apple, is caused by the bacterium Erwinia amylovora. The pathogen can grow on shoots, leaves, or blossoms; enter the plant; and then can grow internally, sometimes killing the tree. At present, growers manage fire blight by spraying trees with the antibiotics streptomycin or Terramycin, which reduce the population size of E. amylovora on the plant surface. Resistance of E. amylovora to streptomycin, which previously was the most effective antibiotic, is now common in many pear-growing regions of the United States.
Frost injury on a variety of agricultural plants and fire blight of pear and apple can be suppressed by Blight-Ban®, a product composed of the bacterial-control agent Pseudomonas fluorescens A506. After even a single application of Blight-Ban, large populations of P. fluorescens A506 can develop on treated leaves or blossoms. These populations compete with E. amylovora or Ina+P. syringae for limiting nutrients on plant surfaces. The severity of fire blight and frost injury is reduced because the population size of the causal organisms is reduced through competition with the beneficial bacterium. Although A506 has been as effective as streptomycin in suppression of fire blight in many field experiments, it can also be used in concert with conventional practices for management of fire blight. It is naturally resistant to streptomycin and Terramycin, so can be combined with antibiotics in spray programs. The opportunity to integrate chemical and biological control is attractive to growers, who are more likely to adopt biological control initially if risks can be minimized by combining it with familiar and effective methods.
SOURCE: Lindow, S. E. 1985. Integrated control and role of antibiosis in biological control of fire blight and frost injury. In Biological Control on the Phylloplane, C. Windels and S. E. Lindow, eds. St. Paul, Minn.: APS Press.
is sometimes transferred at a slow pace and EBPM will require different and even more information. An intense and well-coordinated information, education, and training initiative is going to be essential to resolve this dilemma and move agriculture from conventional, chemically based pest control to EBPM.
Putter and Van der Graaff (1989) identified four levels of decision makers in the pest-management process: growers, research and extension workers, regulators, and the private sector. Here we expand this list to the following six functional groups: (1) researchers, (2) educators, (3) policy makers and regulators, (4) private business, (5) the general public, and (6) end users. The information each of these groups needs may be different, but facilitating the flow and use of information to and within each group is essential. A breakdown in information flow to one of the six groups may seriously hamper the development and implementation of EBPM, as it has in the development of other technologies. Although the timely and unrestricted transfer of new information between all of these groups is critical, here we will emphasize only the importance of this process to the end users (Figure 2-1).
End users are those who make and carry out pest-management decisions. They include growers, crop consultants, pest control advisors, corporate field representatives, nursery and greenhouse managers, landscape maintenance professionals, forest managers, stock handlers, stored product managers, pest control operators, gardeners, and others. These end users are referred to collectively as pest managers. Delivery of information to this group is crucial to changing from current chemically based pest management to ecologically based strategies. Regardless of the technologies available, if end users do not have a clear understanding of the use and impact of these technologies, change will not occur. Although this is the most important link in the pest-management chain of knowledge from basic research to implementation, the total linkage of information transfer to the end user needs to be strengthened and streamlined.
Putter and Van der Graff (1989) have indicated that pest managers are decision makers, and that sound decisions require sound information. Knowledge, or at least ready access to appropriate information, is essential to successfully and economically manage pests. Efficient information flow is critical to successful pest management because (1) the knowledge needed is complex and a large amount of information is available; (2) there is a diversity of sources of information, both public and private; and (3) pest situations are dynamic and change substantially in both the short term and the long term (Lawson, 1982).
Putter and Van der Graff (1989) stated that growers must be knowledgeable in three areas to successfully manage pests:
they must have information about the pests, including biological characteristics and type and significance of damage;
they must have information about pest control options and the implications of using these options; and
they must be knowledgeable about the economic implications of specific pest-management decisions.
Norton (1982) proposed a general approach that can be used to improve crop protection decision making. This approach can be viewed as closing "information gaps" and consists of a three-step process:
identifying the types of information needed by the pest manager,
identifying how the information is needed, and
analyzing how the information gets to the grower.
Norton (1982) distinguished between "total need" and "specific need" information. To satisfy the total need, the pest manager must be familiar with all options and thus require a breadth of information. For example, the pest manager must know the entire range of cultural controls, biological controls, chemical controls, and host resistance options available. To satisfy the specific need, the pest manager must know detailed information about each of the individual practices being considered. For example, if releasing a natural enemy for augmenta-
tive biological control, the pest manager must know the proper time of release based upon susceptible stages of the target pest(s), rates of release based upon pest pressures and efficacy under different environmental conditions, range of target pests controlled, and cost.
Information has to be provided to the end user at the appropriate technical level, and in a clear and convincing presentation. Both the information and the delivery can take many forms. Although we often think of the formal channels of communication (such as through extension programs, publications, trade journals, or industry advertising), informal channels also play a key role. The innovative end user will be the first to evaluate and adopt new technologies; the actions taken by this person reduce the risk perceived in the rest of the community, and the innovator then becomes an informal resource for his/her colleagues.
Growers will require more ecological and economic information to manage agricultural and forest production systems. Because farms vary in their microenvironment, both spatially and temporally, growers that previously employed similar pest-management strategies may now use different systems. For instance, information of interactions among organisms within the agroecosystem can vary dramatically from the previous season's production system. Such information is more useful in a system which cuts across many interfaces, such as agroecology and economics, hence, enabling a grower to consider a wide variety of circumstances, drought versus a wet season, presence of specific pests, varying commodity and input prices, and a change in crop rotation. Part of an ecologically based pest-management system's success will be on an accompanying information system to help a grower manage the system.
Future pest managers may rely on computer based tools for greater efficiency and precision in decision making. More information on production system management is not only needed, it needs to be very accessible. Growers cannot lose time waiting for information on a timely decision nor can they lose time trying to find an information source. Though this information is not currently available for most agroecosystems, personal computers can improve the success of EBPM.
Researchers can provide growers with operational models to help growers make production decisions more directly. Some of the operational models now used, or that are being developed, are programs to use on a personal computer. An operational model is more effective when researchers work together to ensure accuracy of measurements used in the model; nonetheless operational models may be useful tools for decision making in EBPM.
Demonstrations are an effective means of reducing grower uncertainty to alternative management strategies. An effective demonstration of a new technology is probably the most powerful form of education. Pest-management demonstrations are conducted on university experiment station property or on private farms, often during planned workshops or field days. Such demonstrations also can be conducted by grower networks or cooperatives, Cooperative Extension
personnel, or private business or other public or private agencies or organizations.
Demonstration research needs to be large in scale to reflect actual farming practices and to reduce outside influences (such as movement of arthropod pests and their natural enemies or plant disease spores). Whole-farm demonstrations are ideal, and these should be replicated throughout the area. Further, because local environment, pest pressures, and cropping practices vary from region to region, such demonstrations must be conducted in locations representing the entire range of the crop.
The agricultural information and education infrastructure has changed and adapted to new circumstances since the inception of the land grant colleges in 1862 (Goe and Kenney, 1988). The importance of the public sector in agricultural information was reinforced by the passage of the Smith-Lever Act of 1914, which created the Cooperative Extension Service, a unique cooperation of national, state, and local agencies for the primary purpose of providing practical information to growers. The current infrastructure will have to be retooled and strengthened to meet the knowledge needs for ecologically based pest management.
Historically, extension agents focused predominantly on recommendations for using pesticides, because of the large quantity of information available, the generally high degree of efficacy of the products, the ease of use of pesticides, rapid changes in pesticide use technology, and changes in pesticide use regulations. However, extension specialists recognize a need to increase their educational emphases in EBPM. A 1992 survey of 178 extension entomologists from throughout the United States, for example, found that 18 percent of their educational time was devoted specifically to programs relating to conventional biological control; the respondents indicated, however, that they expected the time would increase to 38 percent within 10 years (Mahr, 1995). This increase will be driven by research developments in biological control as well as by demand from the agricultural community for pesticide alternatives (Mahr, 1991).
Private businesses that rely on pest-management information can be placed in two categories: those with products to sell (such as agrichemical companies, biotechnology companies, and suppliers of biological-control agents), and those that provide a service (such as independent crop consultants). Both groups use information generated in-house as well from external private and public sources.
Product-oriented companies use scientific information (to further their own research on new products), regulatory and policy information, and marketing trends. Some of this information is also passed along to their customers, in the form of advertising, use recommendations, or product profiles. For example, the Association of Natural Biocontrol Producers, which is the association of companies which market predatory and parasitic insects for biological control, has developed a series of ''Product Profiles" on the various types of commercially available natural enemies. Profiles provide information on the general biology of
natural enemies and how they are best used in pest management. Information to develop the profiles derives from both public and private research.
Independent pest-management consultants sell their knowledge about pest control to growers and others who manage pests. As pest management becomes more biologically based, it is likely to become more knowledge intensive; it is therefore likely that private consultants will play an increasing role in pest-management decision making. Consultants require immediate access to new pest-management information, including new techniques and new products. In addition, they conduct their own research and use their own observations to evaluate how new practices and new products perform for their clients. Therefore, consultants routinely take advantage of all possible educational opportunities, including meetings, field days, publications, and trade journals; many of these opportunities such as extension programs, originate from the public sector.
The public sector, such as cooperative extension programs, must continue to have a major role in the delivery of pest-management information directly to growers and pest managers. The public sector is more likely to do environmentally oriented education than the private sector, especially with those important pest-management practices that are not related to commercial products or services. Also, the public sector, because it is not product or profit oriented, is perceived by the agricultural community as being less biased than the commercial sector when evaluating and teaching crop protection and production practices.
Pest-management methods that are effective, economically practical, long lasting, and not damaging to human health and the environment will require knowledge for effective implementation. As pest management becomes more biologically based, it is likely to become more knowledge intensive; this increased complexity will likely generate an increased demand for private consultants who can sell their knowledge about pest control to growers and others who manage pests. The numbers of these consultants is likely to be important for future information dissemination activities.
There is a need to assure educational and training opportunities for such consultants. The need for pest-management professionals has been emphasized by Mumford (1982). Edwards and Ford (1992) noted a lack of trained personnel to collect and process pest-management data for decision making—i.e., pest-management consultants. Alms (1994) advocated professional consultants with technical problem-solving skills who also can interact with the growers to help them change. The lack of well-trained resource people to work one-on-one with growers, either in the public or private sector, will constrain the rate at which ecologically based management systems are implemented.
Few universities have a fully integrated curriculum in plant health or pest management at either the undergraduate or graduate level. A few universities have developed such integrated programs in the past, especially at the M.Sc. level. Three reasons may partially explain the lack of success of such programs:
(1) they were too theoretical without building adequate practical experience into the program, (2) unfunded graduate programs could not compete with research programs providing stipends or assistantships to students, and (3) these programs may simply have been ahead of their time, coming during a period of relatively simplistic approaches to pest management that did not require practical knowledge needed by future practitioners of EBPM.
There is a need for greater coordination and better feedback mechanisms to ensure adoption of new EBPM strategies (Fitzner, 1993; Hoy, 1989; Norton, 1982; Zalom and Fry, 1992). All parties need to be involved in a coordinated process, including researchers, state and local extension personnel, the pest-management industry, end users, environmental groups, and administrators and policy makers.
ROLE OF COLLECTIVE ACTION IN PEST MANAGEMENT
Collective action can increase the successful development and implementation of EBPM. The previous section emphasized the need for information to decrease grower risk and increase adoption of these alternative approaches to pest management. Collective action strategies that unite growers or are the result of public policy can reduce costs and ensure the availability of effective biological organisms, products, or resistant plants.
Economically feasible solutions to solve pest problems often require the coordination and cooperation of growers of the same crop located within the same region. For example, the Fillmore Citrus District of Ventura County, California manages their supply of biological-control organisms and keeps pest-management costs below those of other districts (DeBach and Rosen, 1991). Growers are willing to pay for ecologically based management if they are assured that other members of the cooperative are paying their fair share too (Rook and Carlson, 1985).
Rook and Carlson (1985) assessed factors affecting the participation by North Carolina cotton growers in a private pest-management group over a three year period. The number of hectares in a time-competing crop, farm size, low costs of participation, and high expected cotton yield all contributed to the grower's decision to join the group. Growers that grew a time-competing crop found group management a way to free up time for the other profit making production system. Larger areas planted to the crop means greater vulnerability to damage and, hence, greater probability of joining the group. A cooperative can offer lower prices to growers which relieves some of the economic burdens associated with individual pest control and high cotton yields place a higher value on pest control.
The disadvantage of pest-management groups is that they are not necessarily
set up to meet the unique demands of each grower. The quantity of pest control may be more or less than the needs of an individual grower. Thus, the more similar the needs and characteristics are among a pest-management group, the more likely that growers will join and participate.
Some of the most effective biological-control organisms and products in EBPM are projected to have modest uses or small markets, and will require public sector support for regulatory approval as well as for research. The best cases involve release of self-perpetuating classical biological-control organisms that produce great public good, but which have no commercial viability in the private sector. The costs associated with obtaining registration can discourage commercialization of biological-control organisms, as is the case now for minor use chemical pesticides, products needed on small acreage or in such small markets that they lack commercial appeal. In the same way that public funds help with approval processes of minor use chemical pesticides by regulatory agencies, public investment can ensure continued progress for biological technologies.
Organized efforts to increase distribution of high-quality biological tools will facilitate grower acceptance of EBPM. The procedure of crop seed certification by state agencies guarantees that new cultivars are genetically pure and that noxious weeds, arthropods, and pathogens are below detection limits. Each certification board tests, increases, releases, and distributes new field crops according to predetermined standards (Poehlman and Sleper, 1995). Such a process of release benefits the individual grower with valuable information on product performance and quality, lowering the risk of adoption.
Monitoring for the potential development of resistance by pest organisms is key to managing the long-term viability of ecologically based systems (Gould, 1991). Biological-control organisms, products, and resistant plants are valuable entities and the numbers of these tools that meet the criteria of EBPM—safe, profitable, and durable—must be considered finite. Pest resistance to broad-spectrum, chemical pesticides is a recurring problem. Resistance to Bt, a microbial pesticide derived from Bacillus thuringiensis has also been observed in certain arthropod pests (Gould, 1991; National Audubon Society, 1991). The predominance of resistance biotypes will be directly related to the degree and duration of selection pressure applied to the target pest by the biological-control organism, product, or plant. If resistant biotypes selected from pest populations
Fillmore Citrus Protection District in California
The 3,500-hectare Fillmore Citrus Protective District in Ventura County, California, is a unique cooperative pest-management association. The district maintains its own insectaries to produce biological-control organisms as needed and uses only a minimum of selective insecticides. They have nearly perfected ecologically based management; as a result their pest-management costs are the lowest of any district in California and their fruit quality and quantity among the highest. Between 1971 and 1980, the mean annual cost of pest management in the Fillmore District was only $72 per hectare. This compares to $362 per hectare of Valencia oranges in Ventura County (Graebner et al., 1984).
The Fillmore Citrus Protective District originally was organized in 1922 to assist in the chemical eradication of the California red scale (Aonidiella aurantii), which had just been discovered in several orchards in the district. Prior to about 1940, most of the citrus orchards in the district were fumigated annually with hydrogen cyanide gas or sprayed with oil to reduce the Mediterranean black scale (Saissetia oleae), which was the major citrus pest in southern California at that time. Other pesticides were applied to control a variety of less critical pests.
The importation of a parasitoid, Metaphycus helvolus, from South Africa in 1937 to control black scale marked the beginning of a gradual shift to ecologically based management. This parasitoid has become established and provides good management of black scale. The original release of the parasitoid has been supplemented by periodic release of insectary-reared parasitoids in some Fillmore District groves. For the 10-year period of 1960 to 1970, an average of less than 5 percent of the groves were sprayed each year to manage black scale. This alone amounts to annual savings of $100 per hectare, more than $300,000 per year for the district.
The red scale parasitoid, Aphytis melinus, was imported from India and Pakistan and became widely established in the Fillmore District in 1961. Supplementary releases of insectary-reared Aphytis have been made as needed; nearly 4.5 billion parasitoids have been released since 1961. Since the parasitoid has been used, only about 1 percent of the district has had to be treated with insecticides annually for the California red scale.
In total, 12 arthropods that are serious major pests in other districts or other countries are being completely suppressed by use of biological-control organisms in the Fillmore District. Four of these were major pests at one time or another in the Fillmore District but now are either minor or innocuous due to importation of new biological-control organisms.
SOURCE: from DeBach, P., and D. Rosen. 1991. Biological Control by Natural Enemies. Cambridge, U.K.: Cambridge University Press, Second Edition. Pp. 372-373. Reprinted with the permission of Cambridge University Press.
Campbell Soup Company—IPM Success on a Large Corporate Scale
Because of the greater complexity and more intense management needs of EBPM, questions have been raised about its probable degree of success in large-scale corporate agriculture. This example of the successful implementation of traditional IPM approaches by the Campbell Soup Company addresses this issue.
Campbell Soup Company is a major producer and user of vegetables and other agricultural products. Its primary crop is tomato, but it also has its own mushroom and poultry operations. It contracts with vegetable growers in California, Ohio, Michigan, Texas, New Jersey, and Florida; much of its tomato production is in Mexico. Campbell recognizes the public's concern about pesticide use and residues in food. Therefore, in 1989 it embarked on an ambitious goal to reduce synthetic pesticide applications by 50 percent on crops grown for the company by 1994. Through its contracts, Campbell has encouraged its suppliers to use the latest IPM techniques. This program has resulted in substantial reductions in the use of pesticide and adoption of ecologically based practices.
Campbell's Approach to IPM
Campbell's IPM program includes three interrelated components. First, cultural practices include field selection and crop rotation to minimize weeds and diseases; vegetable varieties are selected based on their resistance to diseases; and field sanitation limits infestations of arthropods, weeds, and pathogens. Second, monitoring for pest activity is conducted at least weekly. The third component is treatment, which is implemented only when necessary and where appropriate, uses ecologically based practices such as sprays of Bacillus thuringiensis for caterpillar control.
Anthrachnose Fruit Rot of Tomato in Ohio
Anthrachnose was the primary disease affecting tomato production in Ohio. Campbell adopted a computerized disease forecasting system, developed by the Ontario Ministry of Agriculture, that determines disease severity based on local weather conditions. Growers using this system used an average of 4.3 fungicide
become dominant, the usefulness of the biological control will be limited. The importance of monitoring pest populations in individual fields is critical to the accurate assessment of tactics aimed at delaying pest resistance to biological control.
Ensuring the durability of biological-control organisms, products, or resistant plants in the agroecosystem must be managed through collective action. An
applications in 1991, compared to 9 applications for non-IPM growers, at a cost savings of $39 per acre. The quality of tomatoes did not decline in the IPM fields.
Virus Abatement in Mexican Tomato Production
In the 1980s gemini viruses were causing serious fruit losses in the state of Sinaloa, Mexico. These viruses are transmitted by whiteflies. Campbell developed a cooperative research program with California, Arizona, and Sinaloa. Geographic Information Systems (GIS) technology allowed for the identification of high-risk fields, which were then planted after whitefly populations dropped to low levels. More attention was paid to field sanitation, which eliminated alternate hosts for the whitefly. Using this approach, both pesticide use and disease incidence dropped substantially.
Lepidopterous Pests of Tomato in Sinaloa
A complex of caterpillars including tomato pinworm, tomato fruit worm, beet armyworm, and yellow-striped armyworm are prominent pests of tomato in Sinaloa. Traditional control of this complex required the use of up to 40 applications per crop of broad-spectrum insecticides. This led to detectable levels of insecticide residues. A variety of ecologically based practices have now been implemented, and their use is based on strict pest-monitoring practices. For example, pheromone mating disruption and microbial insecticides are used for tomato pinworm, and parasitic wasps are produced on site by Campbell and provided to growers for control of tomato fruit worm. This program resulted in the reduction in use of synthetic chemical insecticides in Sinaloa from 22,000 pounds in 1986–1987 to 0 pounds by 1992–1993, at a savings to growers of approximately $76 per acre.
In summary, through the adoption of effective monitoring techniques and the use of various EBPM practices, ranging from field sanitation to biological control, Campbell Soup Company has been able to increase yields, maintain quality, reduce pesticide use and detectable residues, and save its growers more than $1 million in pest-management inputs.
SOURCE: Adams, C. E. 1994. The role of IPM in a safe, healthy, plentiful food supply. Pp. 25-34 in Proceedings, Second National Integrated Pest Management Symposium/Workshop, Las Vegas, April 19-22, 1994.
effective mechanism currently used to delay pest resistance is the coordination of pest control activities among growers (National Audubon Society, 1994); sharing pest monitoring activities and collected information is useful in developing countermeasures that will limit additional crop losses. Practices, comparable to the use of mixtures and multilines to conserve the durability of plant resistance genes, can be developed and put into practice in order to enhance the durability of
valuable biological-control organisms and products. Efforts to do this can be coordinated by industry, perhaps modelled on such organizations as the fungicide resistance working group, which is dedicated towards developing practices and implementation recommendations to enhance the long-term use of fungicides. Cooperative efforts among researchers, industrial suppliers, and growers can increase the durability of these biological tools.