COMPONENT ACTIVITIES OF IPM
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
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,
<click each box to see
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
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,
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.
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.
Figure 2: Impact of arthropods on forest resources and
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
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
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).
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
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.
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
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).
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
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
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 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
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
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.
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
EPILOG TO IPM
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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