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Component Activities of IPM

Pest Population Dynamics

Forest Stand Dynamics

Impact assessment


Forest Database


Treatment Tactics

Environmental Assessment

Management Planning

Decision and Execution




     The major impetus that fueled the development of concepts of IPM came from concern for managing forest insect pest outbreaks on intensively managed public and private forest lands. The research and development projects of the 1970's and 1980's and subsequent investigations have provided a well formulated IPM concept and approach. However, the issue of implementation of IPM within the managerial hierarchy of forest protection-->forest management--> environmental management remains a challenging task. The concepts, practices, technologies, and legal statutes of forest protection, forest management, and environmental management have changed significantly since the architects of IPM crafted the initial principles. In this section we present an overview of the basic activities associated with the practical application of IPM in forests. 
     IPM in forests can be defined as follows: the maintenance of destructive agents, including insects, at tolerable levels by the planned use of a variety of preventive, suppressive, or regulatory tactics and strategies that are ecologically and economically efficient and socially and politically acceptable. It is implicit that the actions taken are fully integrated into the total forest and environmental management process –in both planning and operation.
     From a functional perspective IPM consists of a number of specific, but related, activities as illustrated in Figure (1) (Saarenmaa 1992). This "activity model" is a concise overview of the concept and practice of IPM. It represents a significant advancement over previous constructs in that the research and development components of IPM are integrated with activities needed for implementation of the concept in a real world forest environment. Figure 1 represents IPM to consist of nine separate activities that are related as illustrated by connections and directions of arrows. The basic activities include the following: assessment of pest population dynamics, assessment of tree and forest dynamics, impact assessment, evaluation of control alternatives, monitoring, database management, diagnosis, environmental assessment, 

Monitoring(field and remote sensing) Diagnosis Forest database Treatment tactics Decision and execution Environmental assessment pest population dynamics Management Impacts:social, economic, ecological, political Tree and forest dynamics

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Figure 1: Activities associated with integrated pest management (Saarenmaa, H. 1992. Integrated pest management in forests and information technology. Proc. IUFRO S.207-05. In Dimitri, L. (Ed.) Integrated Control of Scolytid Bark Beetles. Hann. Munden, Germany, 19-22 August 1991.)

management planning, and decision and execution. Each of these activities is examined below. 
     There are eight fundamental principles of IPM in forests that are conveyed in Figure 1:
     1. The basic premise of IPM is that there is a resource or forest condition in need of protection from pests. From a management perspective, the state of the resource is evaluated through an examination of tree and forest dynamics. This examination usually involves use of a simulation model that approximates the expected growth and yield of a valued tree species over at least a rotation period. The condition of the forest is evaluated by integration and interpretation of spatially referenced tabular databases that describe a specific environment. The types of data needed for this purpose include themes such as tree species composition, age, and density; terrain elevation and slope; soil type, etc. 
     2. Insect species are periodically pests because they become sufficiently numerous to damage a valued resource or desired forest condition in some way. Generally, there is a direct relation between population size and impact on forest resources and conditions. IPM, therefore, requires evaluation of pest population dynamics. Again this evaluation can be facilitated through the use of a simulation model. 
     3. The actual or potential importance of a pest species is judged by evaluating its economic, ecological, social, or political impact on values we associate with the resource or forest condition. 
     4. In order to assess the actual or potential impact of a pest species, it is necessary to gather contemporary information about the state of insect populations and the resources and conditions of the forest environment. This activity requires monitoring. To monitor is to observe critically in ways that do not affect the resources and conditions of the forest environment. The information collected during the monitoring activity becomes a part of the forest database. The forest database contains spatially referenced and tabular data that describe the forest resources and condition. 
     5. The contemporary information gained through the monitoring activity is used in diagnosis of the cause and extent of a pest problem. This diagnosis is used to establish the need for directed suppression or prevention actions. Human judgement by experienced individuals is often an important component of the diagnosis. 
     6. Pest population size can be modified (e.g., pesticides) or regulated (e.g., natural enemies) by the application of treatment tactics

Click picture to see big image!

Figure 2: Impact of arthropods on forest resources and conditions.

The procedures may be targeted to suppression of existing populations or prevention of forest conditions that lead to pest outbreaks. 
     7. Decisions to consider application of specific control tactics must be evaluated for their effect on the forest management plan and their environmental impact. These activities link forest protection to the higher levels of the management hierarchy, i.e., to forest management planning and environmental assessment. 
     8. Decision and execution of an IPM program follows from interpretation of the environmental assessment and an evaluation of the effects on the forest management plan. Typically, this activity (decision and execution) requires integration and interpretation of both qualitative and quantitative information and computer based decision support is often a necessity. The results of the decision and execution activity directly affect the pest population and forest tree dynamics. 

     In the following discussion we examine each of the basic activities associated with IPM. 

Pest Population Dynamics
    Pest population dynamics is the study of change in the distribution and abundance of an organism through space and time. The spatial framework for pest species encompasses a range of square centimeters to hectares and the temporal framework may vary from minutes to years. Within this spatial-temporal framework, it is possible to focus attention on populations within a unit of habitat, within a stand, or within a forest landscape (Coulson 1979, and Coulson and Wunneburger 2000). 
     Pests are of major importance in forest management because they are the agents that consume resources, alter the conditions of the forest landscape, and disrupt management plans and schedules. Our interest in managing pests includes immediate short-term response to outbreak conditions involving current population levels and damage as well as long-term planning to anticipate and prevent population levels that lead to outbreaks. Obviously, the approaches used in population management under these two circumstances are quite different.
     When one considers all the variables that affect birth, death, immigration, and emigration in a population of forest insects, it is not surprising to find that mathematical models of population systems are utilized to abstract key elements (Gutierrez 1996). The accuracy and precision of predictive models of population dynamics are related to space-time resolution. Both accuracy and precision diminish as the space-time framework is enlarged, primarily because of the difficulties in forecasting weather over long periods of time. Therefore, best results in modeling populations have been obtained at the stand level of organization and in a period of time ranging from several weeks to several months. In management planning for potential pest problems, variables such as stand age, species composition and density, localized site conditions, physiographic conditions, and climatic zones within the range of a particular pest species are used in predicting the likelihood of pest problems occurring at various age intervals of forest growth. 

Forest Stand Dynamics
     The forest stand is often the focal point of IPM because it is the basic unit used by foresters for inventory, planning, and operations. Stand dynamics includes consideration of causes for changes in the distribution, abundance, and size of a host tree species through space and time. 
     In the context of IPM, we may be interested in either (1) the role of pests (insects, diseases, etc.) in the population dynamics of the host tree species or (2) the role of the host in the population dynamics of the pest. In the first case, where interest is in the role of pests in the population dynamics of the host, the temporal framework spans the rotation time for a particular tree species, which can range from ca. 6 to 200 years. The spatial framework will normally be in hectares. We emphasized earlier that specific pests are associated with a particular tree species, age-class, and plant anatomic parts. Therefore, during the period from seed to mature tree, many pest species, as well as other biotic and abiotic agents, have the opportunity to affect tree growth rate and survival. In the second case, where we are interested in the role of the host in the population dynamics of the pest, the spatial framework can range from a single tree, to stands, and to forests comprised of stands in different age classes. The temporal framework can span from hours to several years. Host trees vary in susceptibility to colonization by insects and suitability as food and habitat. Tree species, age, and general vigor are variables that influence both susceptibility and suitability. Furthermore, many tree species possess defense mechanisms that deter insects; for instance, the resin system of pines is considered to be a primary defense against certain bark beetle species.
     Foresters have developed mathematical models to predict forest stand growth and yield for many of the commercially important tree species. Data for these models are collected as part of the normal forestry inventory conducted on federal, state, and private lands. Growth and yield models have proved to be useful in IPM, particularly when we are interested in defining costs associated with tree mortality or growth reduction resulting from the activities of pest species. 
     Significant advances in both the theory and practice of spatial modeling of forest landscapes have been made in recent years (Gustafson 1998, Mladenoff and Baker 1999, and Rauscher 2000). Major emphasis has centered on advancing scientific understanding of forest landscapes (e.g., forest succession and disturbance, vegetation dynamics, impact of deforestation, harvesting effects on landscape structure, etc. (Mladenoff and Baker 1999) and on applications to enhance forest management practice (e.g., forest management decisions for wildlife, decision analysis for forest ecosystem management, assessment of watershed condition, etc. (Rauscher 2000).

Impact assessment
     The concept of pest impact on forest resources and conditions is a central issue of IPM. Impact is broadly defined to mean any effect on the forest environment resulting from the activities of insects. From an ecological perspective forest insects can act as herbivores, carnivores, or detritivores. Through these activities insects can cause changes in forest conditions (the abiotic environment, biotic environment, and forest configuration) and valued forest resources (timber production, hydrology, fish and wildlife, recreation, grazing, real estate, biodiversity, endangered species, cultural resources, and non-wood forest products). The degree of insect impact is evaluated using ecological, economic, social and political criteria (Figure 2). 
     Typically, for an insect (or other arthropod) to be considered a pest, in a forest management context, the impact must be substantial, i.e., of sufficient magnitude to cause a human reaction. Because any reaction will involve expenditure of capital (human or monitory), pest management programs are often associated with high value forest environments, i.e., intensively managed forest, specialized forestry settings, and urban/suburban forests. In these environments, the reaction is to suppress or prevent the activities of phytophages or anthropophages. 
     Evaluating impacts can be extremely complicated. A particular insect can have both negative and positive impacts depending on the criteria used in judgment and the particular forest management goal. For example, a defoliating insect could, at the same time, reduce incremental growth of a host tree species, provide nutrient enrichment to the forest, and serve as food for fish. The first impact would usually be considered negative, whereas the second and third would be positive. Because of the difficulties involved in assessing impacts, it is not surprising to find, again, that mathematical models are used for interpretative as well as predictive purposes. 
     In the activity dependency diagram for IPM (Figure 1), impact evaluation involves a reciprocal interaction with the pest population dynamics and tree and forest dynamics components. The results of the impact evaluation feed directly to the environmental assessment component. This flow illustrates how forest protection activities link directly to the upper echelons of the management hierarchy. 

     Recall that to monitor is to observe critically in ways that do not affect the resources and conditions of the forest environment. Monitoring involves collecting data about the forest environment. Forest landscapes are monitored for a variety of reasons, e.g., (1) to inventory the resources and conditional states of the forest environment, (2) to demonstrate compliance with legal forest management statutes, (3) to evaluate the impact of disturbance events, (4) to survey the activities of pest organisms, etc. 
     In the context of IPM, surveys involve monitoring tree and forest dynamics and the distribution and abundance of actual or potential pest insects or the damage they cause (Figure 1). There are several types of insect surveys that can be applied in intensively managed forests, specialized forestry setting, and urban/suburban forests. Forest surveys can be quantitative or qualitative with regard to the type of data collected. Surveys are often classed according to their purpose in the following way: (1) detection surveys, (2) biological evaluations, (3) loss or damage surveys, (4) pest control evaluations. The specific procedures used depend on the type of forest situation being sampled, the type of survey being conducted, and the intended use of the data collected. 
     The data collected in a survey are used for two purposes: to diagnose the nature and extent of the pest problem and to enrich the forest data base (Figure 1). Because of the importance of correct and contemporary information for use in IPM decisionmaking and the high costs associated with surveying pest populations, advanced technologies are often used to capture (remote sensing) (Sample 1994), analyze (spatial statistical procedures) (Gustafson 1998), display (geographic information systems - GIS) (Vitek et al. 1996), and interpret (decision support systems - DSS) (Coulson et al. 1999a) survey data. 

Forest Database
     Accurate information on the state of the environment is a critical component of all forest management programs. The data that provide information about the forest environment are collectively referred to as the forest database. The database contains numerical data that describe different attributes of the biotic and abiotic forest environment. The database can also include data on the condition of the atmosphere. Historically, forest landscapes have been organized for management purposes using a hierarchical system. For example on national forests in the US, the basic unit of organization is the stand. Stands are aggregated into compartments. Compartments are combined to form a ranger district. Ranger districts are combined to form a national forest. Commercial timber companies use a similar system for private forest lands. The basic unit of forest management does not have to be the stand. Landscape management practices could, for example, use the boundaries of a watershed to delimit a management unit. Multiple watersheds could be clustered in manner analogous to the compartment configuration. However, the specific numerical data comprising the various themes of the database are associated with a basic management unit.
     Because the forest database is complex, GIS and database management technologies are used to organize, integrate, and display information. Typical spatially referenced themes represented in the database include: a base map, vegetation types, forest tree inventory, terrain features, hydrography, road corridors, etc. Very detailed data about the management unit can be stored in a separate database management system and accessed, manipulated and displayed in the GIS. The forest database is used to store the results of monitoring and to guide management planning (Figure 1). 

     To diagnose is to recognize and identify by examination and observation. There are two aspects of diagnosis: the first involves identification of the cause of the pest problem and the second involves evaluation of the extent damage. Monitoring forest insects, through the various types of surveys, provides basic information about the activities of pest species. The surveys are often routinely scheduled for important pest species. For example, most of the States in the southern US conduct aerial surveys to detect the presence and estimate the abundance of the southern pine beetle, D. frontalis. These surveys are usually initiated in April and May. Diagnosis is closely coupled with monitoring. It involves inspecting infestations on the ground (ground checking) and verifying the causal agent after pest activity has been detected. The pest species could be D. frontalis or another bark beetle species. Verifying the pest to be D. frontalis is important, as this insect is capable of causing significant tree mortality. However, there are other instances where unexpected outbreaks of pest insects occur. For example in 2000-2001, the red oak borer, Enaphalodes rufulus (Halderman) (Coleoptera: Cerambycidae) was found infesting large areas of hardwood forests in Arkansas and Missouri, US. This insect normally is considered to be a minor pest, but, in this instance the population size was sufficient to cause wide-spread mortality to a variety of red oak species. Diagnosis involved examination of the host material to identify the causal agent and an appraisal of the extent of damage that occurred. 
     Forest entomologists (and forest pathologists) diagnose the cause and extent of pest problems. Their diagnoses are based on fundamental understanding of insect pests and the damage they cause. This understanding is founded on knowledge of the natural history of the pest species. 
     Diagnosis often includes consideration of experiential knowledge provided by foresters who are familiar with a particular forest environment, i.e. diagnosis is a collaborative activity that may involve the technical expertise of more than one specialists. Because it is often difficult to assemble technical specialists to address each forest pest problem, computer-based technologies have been employed to capture the heuristic knowledge experts. Expert systems, which are computer programs designed to mimic the reasoning process of human experts, are suitable for this purpose (Coulson and Saunders 1987, Saarenmaa 1992 and 1994, Saunders et al. 1993, Stone et al. 1986). 

Treatment Tactics
     One outcome of the diagnosis activity can be that an insect pest is causing sufficient impact to warrant human intervention. Treatment tactics are planned procedures that are used to modify or regulate the distribution and abundance of a pest species. As with the other elements of IPM, treatments have time and space components. That is, we are interested in ways and means of suppression of an existing pest population and in prevention of potential pest population outbreaks. In the case of suppression the time frame may range from several weeks to months and the space framework from single trees to stands. However, more than one stand within a forest landscape can be affected. In the case of prevention our time framework may span the rotation period for a tree species and the space framework includes stands within forest landscapes. Obviously the procedures used in suppression and prevention are quite different.
     Historically, a great deal of attention has been given to development of treatments for specific pest problems. Conceptually, these tactics affect reproduction, mortality, immigration, and emigration. There are numerous ways to manipulate these population system components. The specific procedure is often referred to as a control procedure or control tactic. It is not our intention here to review all the procedures used against forest insects. Following are several examples that illustrate various tactics used in suppression and prevention. 
     Suppression tactics are directed to existing pest populations. Examples of tactics are: (1) biological control, including augmentation of insect parasitoids, insect predators, avian predators, and disease; (2) chemicals, including various pesticides and herbicides; (3) behavior chemicals, including compounds that result in attraction and dispersal; (4) utilization, which involves harvesting of infested host materials; (5) various mechanical procedures, including felling infested hosts and burning infested hosts, and (6) use of genetically altered (transgenic) host plants. 
     Techniques used in prevention of insect outbreaks include (1) regulatory controls, which are designed to prevent introduction of pests into uninfested forests or contain them (through quarantine) in localized areas and (2) cultural or silvicultural controls that include management of stand characteristics such as species composition, age, and density; site maintenance; and avoidance of disturbances to both stands and sites. 
     The concept of IPM stresses that a variety of tactics can be used simultaneously to manage pest populations. These tactics collectively constitute a strategy. It is possible to develop strategies for both suppression or prevention goals. For a particular treatment tactic to be included as part of a strategy, it must be efficacious, safe, cost-effective, legal, and socially acceptable. Reference to Figure 1 indicates that treatment strategies are directly linked to environmental assessment. 

Environmental Assessment
Environmental assessment deals with evaluating change to the environment resulting from human actions. In the context of IPM, assessment centers on evaluating change in the environment resulting from suppression or prevention activities associated with forest protection. In particular we are interested in the effects of proposed IPM actions on the forest environment. The terms effect, impact, and consequence are used interchangeably. 
     In the US, the substance of environmental assessment is defined by the National Environmental Policy Act of 1969 (as amended) - (NEPA). This act requires that federal agencies assess the environmental impact of implementing their major programs and actions. For projects or actions that are expected to have a significant effect on the quality of the environment, the responsible agency is required to file a formal environmental impact statement (EIS) (Jain et al. 1993). The EIS is a substantial undertaking and involves the preparation of a document that addresses the following key issues for a proposed action (Jain et al. 1993):
     1. The environmental impact of the proposed actions.
     2. Any adverse environmental effects which cannot be avoided should the proposal be implemented.
     3. The alternatives to proposed actions.
     4. The relationship between local short-term uses of the environment and the maintenance of enhanced long term productivity. 
     5. Any irreversible and irretrievable commitments of resources which would be involved in the proposed action should it be implemented. 
     The environmental assessment activity follows from the selection of specific treatment tactics and consideration of the impact of the pest species on forest resources and conditions (Figure 1). The need for IPM actions is often a result of an insect outbreak which was not anticipated or predicted. In these instances, it is difficult for the responsible federal agency to develop an EIS and provide for protection of valued forest conditions or resources in a timely manner. This dilemma is one of the challenges of forest protection. Environmental assessment is a complex, costly, and slow process. 
     It is noteworthy that the initial models of IPM did not explicitly address the issue of environmental assessment. This activity is a key component of the contemporary view of IPM that is addressed formally for public lands through the NEPA – EIS mechanism. It is dealt with directly on private forest lands through the sustainable forestry certification programs and specific environmental statutes. 

Management Planning
The goals of forest management vary among the different types of forest environments. The management plan for a specific forest environment will be based on accomplishing defined goals. For example, the management plan for a commercial seed orchard would emphasize profitability. The details of the plan to achieve this end include ways to maximize production of high quality seed (which the customers require) while minimizing the coasts associated with the operation. The management plan employed by a city government for an urban forest might emphasize scenic beauty as its management goal. The details of the plan to achieve this end would be substantially different from those used by the seed orchard manager. In the US, the management goal for public forests is sustainability while providing goods and services to citizens. The National Forest Management act of 1976 (as amended) specifies this goal. The landscape management model discussed in Chapter 5 defines the general philosophy and scientific basis for the goal. How to achieve this goal is defined by the National Forest System Land and Resource Management Planning rule (as revised). The current rule describes the framework for National Forest System land and natural resource planning (Federal Register 2000). The principal goal for privately owned intensively managed forest properties is profit from the sales of goods and services. The plan to achieve this goal typically will emphasize ways to maximize growth and yield, minimize taxation liability, and minimize negative environmental impacts. The certification programs for sustainable forest management and legal statutes provide boundaries that constrain the management plan. 
     Pest insects are associated with all of the forest environments and, therefore, management plans must consider their impact. In production forests, insect consumers directly compete with humans for resources. IPM is the approach used to deal with insect pests when they disrupt our planned uses of the forest environment. 

Decision and Execution
The final component of the IPM activities model is decision and execution (Figure 1. This activity involves both judgement and directed action. The issues associated with these two components are quite different and we discuss each in turn. 
     The judgement (decision) component of IPM is an integrative step. To reach this position in the IPM model we have had to participate in eight other activities (see Figure 1). The data and information that form the knowledge base for a specific forest management problem involving pest insects (and diseases) often come from several different domain specialties, such as, entomology, forestry, ecology, geography, sociology, and economics. The knowledge base can exist in several forms: (1) tabular information (usually stored in a database management system, (2) spatially referenced data themes (usually associated with a geographic information system, (3) numerical output from simulation models and mathematical evaluation functions, (4) unstructured paper and hypertext documents, and (5) heuristics of experts (based on corporate experiences of humans (Coulson et al. 1996 and Coulson et al. 2000). Given this complexity, integrative computer-based technologies have been used to aid in supporting the decisionmaking process of the forest manager (Coulson and Saunders 1987 and Coulson et al 2000). A variety of approaches have been employed and Schmoldt (2001) reviews applications developed specifically for insects and diseases, e.g., Potter et al. 2000 - (gypsy moth), Power and Saarenmaa (1995) - eastern hemlock looper, Reynolds and Holsten (1996) - spruce beetle. Synthesis for planning, problem-solving, and decision support involves the use of both qualitative and quantitative information. It is a challenging task that is the focus of considerable ongoing research and development. 
     The directed action (execution) component of IPM involves application of one or more of the tactics available for pest population suppression or prevention of damage. The arsenal of weapons includes chemical pesticides, biological control with natural enemies, mechanical or physical methods (e.g., trapping, habitat destruction, etc.), silvicultural practices, and regulatory (legal) procedures (e.g., quarantines. These actions can be combined to form a strategy for protection that can be integrated into the forest management plan. In some instances the evaluation phase may suggest that the best response to the pest activity is no action. For example, the cost of an insecticide application may exceed the value of the trees in the forest stand or the environmental impact may be greater than desirable. 

In the preceding sections of this chapter we examined the basic underpinning of the concept of IPM. We represented IPM as the principal methodology of forest protection and considered why and when insects (and other arthropods) are considered to be pests. Further we described a model that identified the activities of IPM. The model also considered how the various activities were related to one another. This model was indicated to be a significant advancement over previous representations of the concept, as it integrated the research and development components of IPM and established the functional relation of forest protection, forest management, and environmental management. The initial view of IPM was developed under the multiple-use sustained yield model of forest management where emphasis was placed on insects as competitors with humans for forest resources. The landscape model of forest management considers insects in a broader context that includes both forest resources and conditions. This model of management attempts to balance the negative impacts and positive functional roles that insects play in the forest environment. Nevertheless, forest protection against destructive agents, such as insects and diseases, remains an important component of forest management. IPM is the concept and method used in forest protection to deal with negative impacts of pests on resources and conditions of the forest environment. The activities model of IPM (Figure 1) is complex and has not been fully implemented for any forest insect pest. Portions of it are in operation for many pests. It should be understood that the model can be applied even though not fully implemented. It provides a general framework within which pest managers can plan their activities. It is important to understand how activities are dependent on each other (Saarenmaa 1992).


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