For the Encyclopedia of Food Science and Technology, 2nd Edition
POST-HARVEST INTEGRATED PEST MANAGEMENT
By
Thomas W. Phillips, Richard C. Berberet and Gerrit W. Cuperus
Department of Entomology and Plant Pathology
127 Noble Research Center
Oklahoma State University
Stillwater, OK 74078
2
Effective management of pests within systems where food is produced, processed, and
distributed is critical for maintaining an abundant, affordable, and safe food supply. Over
100,000 pest species are known to cause losses in crop and livestock production, and in
the systems designed for processing and distributing food commodities (1). It has been
estimated that at least one-third of the food supply potentially available to the population
of the United States is lost on an annual basis due to pest infestations during production
and post harvest. In addition, nearly $8.5 billion is spent annually on chemical pesticides
applied in agriculture and industry as farmers and processors attempt to reduce losses (2).
In food production and processing systems, the primary approach to pest control has been
one of eradication, with the objective of total elimination of pest populations (3). This
approach has resulted from concerns, arising foremost in production of fresh fruit and
vegetables, that any pest injury would cause these commodities to become aesthetically
unacceptable to consumers (4). Also, these commodities have such high value that it is
considered unreasonable to risk the possibility of reduced yields or grades of produce (5).
Demands for eradication of pests have resulted in excessive reliance on chemical
pesticides to the extent that applications often been made according to schedules without
assessment of pest infestation levels.
Gradual changes in approaches to pest control are now occurring in food
production, processing, and distribution systems. Whereas there once was little
consideration given alternatives to chemical pesticides, greater interest now exists for
implementation of controls that are less threatening to the environment and non-target
species (6, 7). Integrated Pest Management (IPM) concepts are gradually being
incorporated into the systems that supply food for the world’s population. With
2
3
acceptance of principles of IPM has come willingness on the part of farmers and
processors to implement control programs that are aimed, not at eradication of pests, but
are designed to reduce infestations while monitoring closely the benefits vs. costs of
control measures.
The goal of this chapter is to review general concepts that are basic to IPM as
developed in the production agriculture venue and to provide an overview of the current
issues, methodologies and practical concerns relevant to pest management in the postharvest food industry. The topics included pertain to management of insects or other
arthropod pests that infest durable commodities such as grains, nuts and dried foods, and
all the processed food products derived from these commodities. Pest issues related to
post-harvest handling of fresh commodities will be discussed briefly. Canned or
otherwise processed fruits and vegetables are discussed in other chapters of the
encyclopedia as is prevention of microbial contamination.
WHAT IS IPM?
Integrated pest management is a systematic approach to pest regulation that emphasizes
increased sampling to assess pest infestation levels and promote improved decisionmaking so that control costs can be reduced and social, economic, and environmental
benefits can be maximized (8). From the standpoint of benefit/cost in IPM, the basic goal
of control programs is defined by the concept of economic injury levels. The economic
injury level (EIL) is defined as the pest infestation level at which the loss due to pest is
equal to the cost of available control measures. The EIL concept is used as the basis for
determining economic thresholds (often called ‘action thresholds’), defined as the level of
infestation at which the potential loss due to a pest infestation exceeds the cost of an
3
4
available control measure. In decision-making regarding chemical pesticide applications,
the economic return from use of a pesticide is maximized when the application is made at
the time the pest population reaches the economic threshold level. Implementation of
IPM has typically resulted in reduction of purchased inputs because of more effective
assessment of pest infestation levels and well-defined criteria for determining when
controls are warranted. In crop production systems, programs involving entomologists,
plant pathologists, weed scientists, and economists working together have yielded costefficient tactics for suppressing pests while limiting contamination of the environment
and the harvested food commodities. Integrated pest management concepts are now
being emphasized for post-harvest systems with employment of benefit/cost principles to
guide pest control decisions in storage and distribution systems just as has occurred in
field settings. Considering ecological, as well as economic concerns, IPM is regarded as
an essential approach to preserve a safe food supply and healthy environment, while
keeping U. S. agriculture competitive and profitable.
Explaining the context in which the terms pest and management are used can be
quite helpful to understanding concepts of IPM. The term pest has historically referred to
insects, weeds, plant pathogens, and rodents that compete for resources valued by humans
in production, processing, and distribution systems for agricultural commodities. Thus,
species attain pest status in the context of their association with plant and animal species
used by humans as sources of food and fiber. The abundance of these species, and hence
their importance as pests, is often enhanced in modern production and distribution
systems for agricultural commodities because these systems result in abundant habitats
and vast supplies of resources unlike anything that occurs in natural ecosystems.
4
5
Integrated pest management employs decision-making processes needed to
produce commodities in carefully planned systems intended to keep pest populations
from reaching economically damaging levels, while maintaining profitability of the
enterprise with limited adverse environmental and social effects. The process of
managing pests has significantly broadened in definition and scope over the past 30 years
from unilateral controls applied against single species; to integrated controls employing
multiple tactics against single species; to IPM programs designed to regulate insect pests,
pathogens, and weeds in production systems; and finally, to quite broad concepts of biointensive IPM (1) and integrated resource management (9). There is a substantial need
for increased research and implementation efforts to keep pace with the theoretical
development of management concepts. Practical aspects of implementation have tended
to lag far behind IPM theory (1).
DEVELOPMENT OF IPM PROGRAMS
Basic changes in decision-making processes are important to development of effective
IPM programs. In the past, eradication of pests was often the primary objective, now
programs must address ecological, economic, and health-related concerns in conjunction
with acceptable levels of pest regulation as defined by the EIL concept. Integrated pest
management programs require time and expertise devoted to assessment of problems and
decision-making to gain maximum returns on inputs such as chemical pesticides.
Significant resources must be committed to training of personnel or hiring consultants
who have the necessary expertise to accurately monitor production fields and post-harvest
facilities for the presence of pest infestations and decide on appropriate management
options. Before IPM programs were developed, many applications of pesticides were
5
6
made according to schedules as insurance or prophylactic treatments. However, current
trends in response to economic, environmental, and social concerns addressed in
conjunction with IPM programs require greater time commitments for assessment of pest
infestation levels to assure that controls are employed in the most judicious manner.
As has been learned in field settings over the past 30 years, food processors and
distributors must now realize that most pest management decisions have consequences far
beyond the time and location that pests must be controlled. Comprehensive plans for pest
management greatly improve effectiveness, profitability, and safety of pest control efforts
over what can be achieved with piecemeal approaches. Important keys to effective,
profitable, and environmentally-safe pest management are careful monitoring of pest
populations, complete records of infestation levels and controls applied, and
comprehensive benefit/cost analyses. To provide necessary training and technology, IPM
programs must be supported by multidisciplinary research and extension efforts through
the USDA and Land-Grant universities working in cooperation with the food industry.
The broad range of control options now available for incorporation into IPM programs
include:
1. Biological Controls = using natural enemies such as parasites, predators,
pathogens, and competitors of pest species in applied control programs.
2. Cultural Controls = methods such as tillage, host plant resistance, and crop
rotation to reduce pest infestations in production systems.
3. Chemical Controls = a variety of chemical toxicants, repellents, protectants,
growth regulators, germination inhibitors are used to regulate populations of insect pests,
plant pathogens, and weeds.
6
7
4. Mechanical and Physical Controls = approaches that have their greatest
application in post-harvest pest management include heat and cold treatments, sanitation,
and protective packaging.
5. Legislative Controls = imposition of inspection and quarantine regulations to
prevent importation and spread of introduced pests in living plants and animals or in
harvested commodities.
Integrated pest management programs feature combinations of the above control
options to achieve the safest and most cost-effective regulation of all types of pests in
food production, processing, and distribution systems.
SETTING THE STAGE FOR IPM: THE PESTICIDE ERA
Throughout most of the history of agriculture, a lack of highly effective, unilateral control
measures such as modern-day chemical pesticides resulted in use of various combinations
of controls (e.g., integrated control) to reduce losses caused by pest species. Controls
included a variety of cultural measures such as cultivation and crop rotation; removal of
insects and weeds from crops by hand; and application of inorganic pesticides containing
active ingredients such as sulfur, lime, and arsenic. It was not until the advent of the
“modern insecticide era” after World War II that use of highly effective compounds like
DDT and BHC (benzene hexachloride) introduced a new philosophy of pest control.
Within a few years of their first applications, these organochlorine insecticides were
being used extensively with the objective of eradicating pest populations. Little concern
was given the potential for deleterious consequences to non-target species, hazards to
farm workers, or harmful residues in human food. The ready availability and high degree
of effectiveness of these pesticides resulted in reliance on them as a unilateral controls.
7
8
By 1966, nearly 150 million pounds of insecticides were being applied per year in the
United States, most of which was used in crop production (10). Although insecticides
were the first of the chemical pesticides to be used in such vast quantities, research efforts
led to discoveries of phytotoxic chemicals that resulted in usage of herbicides which
peaked at over 450 million pounds per year in 1982 (10). The increase in the quantity of
fungicides applied has been much more modest, from 21 million pounds in 1966 to 37
million pounds in 1992 (2).
Certainly, the availability of highly effective chemical insecticides has been an
important factor contributing to significant reductions in incidence of arthropod-borne
diseases in humans and domesticated animals. Also, availability of effective chemical
pesticides of all types has been an important contributor to a 230% increase in
productivity of agriculture in the United States from 1947 to 1986 (11). Ease of
application and relatively low cost of these broad-spectrum pesticides have been
important assets resulting in their tremendously high levels of use in food production and
processing systems. By 1970, insecticide use in cotton in the United States had exceeded
70 million pounds per year. By 1985, herbicide use in corn alone had reached 250
million pounds per year (10).
This extensive reliance on the chemical pesticides has led to some serious
problems and resulted in many questions relating to continued use of these compounds.
These questions have resulted in the cancellations of registrations for many uses of these
products. In extreme instances, as many as 40-60 applications of pesticides have been
made per year in cotton (12), with the result being serious issues of environmental
pollution and mortality of non-target species. Among the problems resulting from
8
9
excessive use of chemical pesticides are the following:

Environmental contamination where pesticides in soils have entered
surface and groundwater threatening the safety of water supplies for
human and animal consumption (2, 10).

Increasing human health risks resulting from exposure to residues in food
and water supplies, particularly relating to the potential of some pesticides
to cause cancer, disrupt the endocrine system, and interrupt normal
development of the central nervous system in children (2). Despite
cancellation of registrations for nearly all organochlorine insecticides,
residues of these compounds are still commonly detected in food products.

Threats to non-target organisms such as wildlife species in both terrestrial
and aquatic environments (2).

Mortality of beneficial parasitic, predatory, and pathogenic species that
often serve important roles in regulating pest populations (2, 13).
Destruction of beneficial organisms contributes to problems of pest
resurgence and outbreaks of secondary pest species.

Development of resistance in pest species to chemical pesticides is a
growing problem for all types of pests worldwide, with over 400 arthropod
species, over 100 species of plant pathogens, and over 50 species of weeds
exhibiting resistance to insecticides, fungicides, and herbicides,
respectively, by 1986 (14).

Increasing costs associated with intensive usage of chemical pesticides in
crop production (10).
9
10
The increasing urgency to find solutions to the problems listed above has resulted
in passage of several major pieces of legislation by the federal government in the United
States. The Federal Environmental Pesticide Control Act of 1972, comprised of
extensive amendments to the Federal Insecticide, Fungicide, and Rodenticide Act of
1947, and the Food Quality Protection Act of 1996 will continue to have great impacts on
availability and use patterns for chemical pesticides for the foreseeable future. These
problems have also generated great emphases for research and extension efforts to
develop and employ alternative controls.
SETTING THE STAGE FOR IPM: ENTERING THE IPM ERA
Although environmental contamination and food safety concerns have resulted in some
increased interest in development of integrated control programs to reduce reliance on
chemical pesticides, the major impetus for reduction in usage of these compounds has
resulted from political activism. Publication of the book Silent Spring by Rachel Carson
(15) served as a catalyst resulting in a strong negative reaction by the general public to the
extensive use of chemical pesticides, especially the organochlorine insecticides such as
DDT. Public reaction to threats of environmental pollution and contamination of the
food supply by pesticide residues (16) has resulted in cancellation of all registrations for
most organochlorine insecticides. Although insecticides belonging to the
organophosphate and carbamate classes replaced the organochlorine compounds for most
uses, growing support among farmers and consumers for integrated control programs has
resulted in reduced reliance on these chemical insecticides and movement from an
industrial to an ecological model of pest management (17).
Public support for the IPM concept has led to gradual development of a
10
11
philosophy that integrates pest control tactics and crop management from both agronomic
and economic standpoints (18). From an original, relatively narrow focus on field-crop
production (19), application of principles of IPM has now attained a much broader focus
to include processing and distribution systems for food commodities. In relation to crop
production, application of IPM provides a basis for continued profitable production of
food and fiber commodities with much less threat of environmental degradation or
harmful residues in food. Employing principles of IPM in processing and distribution of
commodities is an additional, important step in maintaining a safe and wholesome food
supply.
FOOD SAFETY AND IPM
Many countries maintain strict guidelines for the wholesomeness and safety of food
products sold to end-user consumers. Food products must be free of contamination by
harmful chemical residues and biological organisms, such as insects or microorganisms.
They must also comply with standards of purity, composition, and preparation that are
specified by regulatory agencies (20). The food safety challenge for industry requires
delivery of products that are free of pest contamination while also containing pesticide
residues that are below legal minimum levels.
Pests, Pesticides and Regulations
11
12
Hundreds of species of insects, mites, and microorgansims are known to infest grain and
other raw commodities in storage, and many of these same organisms infest grain-based
food products after processing and packaging. There is often an additive effect in terms
of damage caused with infestations by multiple species. For example, infestation of bulkstored grains by insects can result in weight loss of the grain, as well as, increased heating
and moisture levels that facilitate growth of molds and spread of mycotoxins. The end
result of these combined infestations by insects and molds is that grain may be rendered
unusable (21).
Most insects infesting grain being prepared for milling can be removed with
sieves before grinding into flour, however, eggs of some species may survive cleaning
and contribute to subsequent infestations in processed foods. Additionally, insect larvae
and pupae inside grain kernels can not be removed, but are milled with the flour and
remain as fragmentary contaminants. Insect fragments, rodent hair, feces, and other
foreign material, are classified as filth that must be kept below acceptable levels. Though
not toxic, insect fragments can have direct human health effects as allergens for some
persons (22). Contamination by insect-related filth signals an overall low level of quality
and wholesomeness of food products.
Chemical insecticides are used in two principle ways to limit infestation of stored
grains by insects. Insecticides in the form of residual protectants are used quite
commonly as grain enters storage facilities to prevent infestation during storage (23).
Fumigant insecticides are used to eliminate insect infestations that have developed after
commodities are placed in storage. Fumigants such as phosphine and methyl bromide
leave little or no residue that may contaminate food. For this reason, they are not
12
13
considered significant threats to food safety, however, the lack of residual effects with
these chemicals means that they do not protect grain from re-infestation following
treatment. By contrast, residual protectant insecticides used to treat raw grain and applied
throughout the food system in the treatment of structures and equipment where foods are
processed and packaged foods stored may pose problems through contamination by
residues. Insecticide residues can remain in stored grain for months or years because the
storage environment having low light or darkness, stable or gradually changing
temperatures, and relatively low moisture levels slows chemical degradation. Milling,
and to a greater extent, baking or cooking do cause substantial degradation of residues.
However, some residues may still remain as the original chemical used in treatment or in
the form of degradation products (24).
Pesticide residues in food pose both proven and suspected health risks to humans
and generate much public concern and governmental regulatory action throughout the
world (25). The commonly used residual insecticides applied in grain storage facilities
belong to the organophosphate and pyrethroid chemical classes. In the United States,
relatively few organophosphate insecticides are registered for application directly to
grain, however, additional organophosphates and certain pyrethroids can be used in
structural surface treatments (23). The Codex Alimentarius Commission has established
international guidelines for permissible residues of organophosphates and pyrethroids in
both raw grain and processed food products. Individual governmental regulatory agencies
in most countries have generally concurred with these guidelines by passing appropriate
regulations for enforcement.
In the United States, surveys of stored grain for detection of for pesticide residues
13
14
have not revealed levels above established tolerances, however, the majority of samples
have contained detectable residues of organophosphates (Table 1). In spite of evidence
for compliance by the food industry with established tolerance levels for pesticide
residues, consumer advocacy organizations have called for stricter tolerance guidelines.
The Food Quality Protection Act (FQPA) passed by the U.S. Congress in 1996 mandates
a reassessment of all existing pesticide registrations with strict attention to human safety.
The FQPA emphasizes accumulated risk resulting from exposure to classes of chemical
pesticides, not just to individual active ingredients. For example, all organophosphates
used in a variety of applications to food commodities, inside homes, on lawns, and in
public areas will be considered together in estimating accumulated exposure. Risks will
be assessed based on the most sensitive members of the population, that being infants and
children. Residues in food appear to constitute the highest exposure risks because they
result in direct ingestion of pesticides.
Organophosphate insecticides have been targeted as a class for initial review and
potential elimination by the U.S. Environmental Protection Agency because of their
activity as neurotoxins and their potential as endocrine disruptors (26). Cancellation of
registrations for organophosphates currently applied to grain and used throughout the
food industry would creat a great need for effective controls as replacements.
The fumigant methyl bromide is a fast-acting, residue-free chemical that is used
routinely in grain storage bins, flour mills, food processing facilities, and warehouses to
control insect infestations. It has perhaps been the most effective insecticide used in the
food industry, but registrations for this product are slated for cancellation. Because
methyl bromide is an ozone-depleting substance and may pose a threat to the protective
14
15
atmospheric, ozone layer around the earth, its production and application is scheduled to
cease in the United States by the year 2005 as mandated by the Clean Air Act. Other
industrialized and developing countries worldwide are eliminating or severely reducing
use of methyl bromide over the next several decades in compliance with an international
agreement known as the Montreal Protocol (27). In this case, an environmental rather
than a food safety concern is fueling the campaign for cancellation of an effective and
residue-free insecticide for the food industry. This cancellation could possibly lead to
increased use of residual insecticides. Ideal substitutes for methyl bromide have not been
found, but much research and discussion are aimed at developing safe alternatives for the
food industry. One alternative that may become quite important is IPM, an approach that
could keep chemical insecticide usage at a minimum while utilizing a variety of
alternative controls to limit pest populations.
15
16
The Case for IPM in the Food Industry
It seems apparent that the impacts of more stringent regulations on pesticide use in the
food industry in combination with growing consumer demands for more wholesome and
pesticide-free foods must result in more extensive adoption of IPM practices. Although
purchase contract specifications for grain now commonly stipulate that there can be no
detectable pesticide residues, also stipulated is the requirement that the grain be of
relatively high quality with little insect damage (28). In addition, the tolerance levels for
insect contaminants in value-added, finished food products are even lower than those for
raw commodities, essentially a zero tolerance. For the future, it is clear that raw
commodities destined for use in food products must be kept in good condition by
combined action of several preventative measures employed through an IPM program.
Similarly, pest-free, finished products in warehouses and retail outlets that are at risk for
reinfestation must be protected until purchased by the consumer.
Managers at all levels of the food processing and marketing continuum, from bulk
storage of commodities to retail outlets of high-value, finished products, must adopt IPM
strategies that include sanitation, prevention, effective monitoring, and informed
decision-making regarding pest suppression tactics. Informed decision-making based on
cost/benefit analyses is the cornerstone of IPM, and should guide pest control decisions at
all levels of the food industry. The economic injury level concept explained earlier in this
chapter must become the basis for these decisions. Because the relative value of products
varies greatly through the different levels of the food industry, so also will the economic
thresholds used to guide control decisions.
16
17
IPM FOR FOR FRESH COMMODITIES WITH ZERO PEST TOLERANCE
Fresh fruits and vegetables are sold as soon after harvest as possible and there is typically
little time or need for post-harvest IPM. However, IPM is practiced during production of
these commodities to prevent damage, and those involved with post-harvest handling
must be concerned with quality preservation. Only undamaged, blemish-free fruits and
vegetables are selected for the fresh table market. Not only must producers work to avoid
damage that is evident in an exterior examination, but also to eliminate insects confined
within tissues of harvested produce. These pests are not only serious problems for the
domestic market, but in the export market are often the targets of legal quarantines
enforced to prevent the spread of pest species.
Fumigants such as methyl bromide and ethylene dibromide were once commonly
used to insure that fresh fruits and vegetables for export were pest-free (29), but these
chemicals are now being replaced by non-chemical methods. Safe and effective physical
controls are being used commercially, such as cold treatment to eliminate codling moths
from apples and vapor heat treatment to kill fruit flies infesting papayas (30). Ionizing
radiation is an effective treatment for killing immature insect life stages inside fruits and
vegetables while maintaining product quality (31). However, radiation has only limited
commercial adoption for use with fresh produce because of serious opposition in some
locations by consumers who reject irradiated food. Research on controlled atmospheres
using high carbon dioxide concentrations or low oxygen levels shows promise for
controlling post-harvest pests of fresh commodities, but practical limitations in
maintaining proper treatment conditions has hindered commercial adoption of these
methods (32).
17
18
POST-HARVEST IPM FOR RAW, DURABLE COMMODITIES
Although IPM methods discussed here address stored grain almost exclusively, the same
concepts and methods apply to other durable commodities such as legumes, nuts, dried
fruits, and other dried commodities that can be stored in bulk. Cereal and feed grains
comprise the most important basic inputs to the world food supply, and because of their
seasonal growth patterns they must be safely stored and maintained for year-round
consumption.
Grain Storage: Pest Prevention and Sanitation
Insect pest problems in stored grain can be prevented or delayed by limiting access to the
storage facility. With exception of a few species that may infest ripening grain to a
limited extent before harvest, stored grain insects do not infest crops in the field and
normally do not enter storage facilities with the new harvest (33). Insects that become
pests in storage facilities must have dried grains or other appropriate food on which to
feed and reproduce. Typically, the source of insects infesting a newly stored commodity
is from populations already infesting some previously stored material. A common source
of infestation is from residues of grain in ‘empty’ storage structures (bins or silos),
harvesting and conveying equipment, and transportation vehicles. Grain storage
structures and grain handling machines must be thoroughly cleaned of residual grain
before a subsequent crop is stored. If grain is stored in an insect-free structure then the
only source of insects to infest grain is by immigration into the structure. Every effort
must be made to repair leaks and close openings in grain bins and silos to prevent insect
entry. Complete exclusion of insects from grain storages is extremely difficult, but
minimizing entry points does reduce potential routes of infestation. Once storage
18
19
structures are cleaned and sealed, surfaces should be treated with a residual spray of a
registered insecticide to provide protection against insects that may remain hidden within
the structure or that may immigrate into the bin soon after grain is stored.
Monitoring Storage Conditions
Insect population growth in grain is dependent primarily on temperature of the air and/or
grain, moisture content of the grain, and the quality of the grain as a food source (33).
Because most grains and grain products are nutritionally adequate, unless they have been
severely degraded by microbial agents, food quality is rarely limiting for insects infesting
stored grain. Temperature and grain moisture may vary greatly among storage situations
are very important for insect survival and population growth. Biological factors such as
development time from egg to adult, survival rates, and the number of eggs produced by
females all attain maximum levels within optimal ranges of temperatures and grain
moisture. Typically, these life history variables decrease at temperatures and moisture
contents either above or below the optimal zone (Fig. 1).
Insects that feed as larvae
inside grain kernels are more sensitive to grain moisture content than are the external
feeders. Optimal grain moisture levels for growth and survival of internal grain feeders
ranges from 12 to 15%. Optimal temperatures for growth and development of stored
grain insects are between 25 and 32 C. Most species experience mortality or reduced
population growth at prolonged periods above 40 C and cease development below 15 C
(34). It is clear, therefore, that insect population growth can be slowed by maintaining
grain in a cool, dry condition.
19
20
It is essential for effective stored grain IPM to have the best information possible
about the current status of the commodity being managed and the potential pest
populations at any time. As grain enters the storage facility, it should be characterized for
quality factors such as bulk density, percent composition comprised by broken kernels
and foreign material, and moisture content. Information on initial moisture content is
critical because high moisture grain may need to be stored separately, mechanically died,
or later blended with drier grain to attain a composite grain mass that is safe for storage.
The storage structure should be equipped with thermocouple cables or similar
devices to monitor grain temperature at various locations throughout the grain mass
during the storage period. Temperature cables are typically hung from the roof of a
storage structure and extend vertically through the grain mass. Thermocouples are
positioned on cables at a spacing of 2-3 m from bottom to top of the mass and a series of
cables should be deployed at 5-10 m intervals so that the grain mass is evenly monitored.
Temperatures from each monitoring point should be recorded on a regular basis, ideally
weekly or bi-weekly, and any abrupt increases in temperature over a short period of time
should be investigated by sampling the grain mass. Temperature cables are useful in
detecting “hot spots” where moisture, mold growth and insect infestation may have
begun. Temperature monitoring is also important to check the progress of grain cooling
during aeration.
The species and numbers of insects in stored grain can best be monitored by direct
and systematic sampling of the grain, and by use of traps. Direct grain sampling is the
best monitoring approach, but it is labor-intensive and requires a certain level of skill.
Managers of grain storage facilities can easily learn the required methods and implement
20
21
grain sampling for insects as part of their regular commodity management routine.
Samples can be obtained to a depth of 1-2 meters by using a spear-shaped sampler
to withdraw grain from the mass, or sampling may be done as grain is moved from bin to
bin within a facility using a cup-type (pelican) sampler (Fig. 2). Increasing the numbers
of samples enhances the level of accuracy achieved in estimating insect population
density (35). For example, five-1 kg samples must be taken from each 27 metric tons
(1000 bushels) of grain to determine with 90% accuracy if a grain mass contains as many
as 2 insects per kg; a common economic threshold for control decisions. Grain samples
must be processed with an appropriate sieve or sifting device to remove insects for
identification and counting. Grain probe traps are also available that capture insects as
they move through a grain mass (Fig. 2). These traps are effective for detection of insects
at low population densities (36), but the data obtained are not easily converted to numbers
of insects per unit of grain volume.
Decision-making for Insect Control
Correct interpretation of insect sampling data is important for making control decisions in
stored grain IPM. As indicated earlier, decisions should be based on cost-benefit analyses
that incorporate assessments of the quality parameters. Raw grain is marketed based on
quality, which is quantified by a numerical grade in the United States. The highest
quality grain, in addition to having a high bulk density (test weight) and little or no
foreign material, contains no live insects, and has no measurable damage from insects.
Damaged kernels result from feeding within by species such as weevils in the genus
Sitophilus and the lesser grain borer, Rhyzopertha dominica, that chew holes through
kernels. If one or more members of these species are found in a grain sample or probe
21
22
trap sample then more extensive sampling should be conducted. Discovery of damage by
internal feeders may warrant a fumigation treatment to eliminate the infestation and
prevent additional damage.
The presence of large numbers of external feeding insects, which cause no direct
grain damage, may be revealed in grain or trap samples, but they can be tolerated until the
time of sale as long as grain quality, temperature and moisture remain acceptable. Live
external feeding insects can be eliminated with an effective fumigation before grain is
transported. It should be noted that many international markets will not tolerate even
dead insects in grain, so treatment decisions must be adjusted accordingly.
Non-chemical Controls for Stored Grain Pests
Effective IPM programs for stored grain involve a variety of approaches intended to
prevent the occurrence of damaging pest infestations. Sanitation was discussed earlier as
a preventative measure employed before grain enters the storage facility. Among the
most effective non-chemical means for pest prevention or suppression after grain is in
storage is use of ambient air cooling with aeration. This is achieved with air flow from
fans mounted at the base of the storage structure that either blow air into the bottom of
the mass and force it upward, or draw air through roof vents downward through the grain
mass. Effective aeration cooling occurs only when the outside air temperature is below
the temperature of the grain. Thermostatically controlled fans can be used to insure that
they operate at the proper ambient temperatures (37). Because insect developmental rates
are directly influenced by temperature, lowering the temperature of the grain mass below
the optimum level for insect growth (below 15 C for most species) can significantly
reduce population increase and the potential for damage. Low grain temperatures are
22
23
achieved most efficiently in temperate regions after seasonal changes from summer to fall
result in lower ambient air temperatures. However, even if grain cannot be cooled below
15 C immediately, marginal cooling can be effective in reducing rates of insect
population increase (33).
Simulation models of temperature-dependent insect population growth rates have
been developed for the most damaging stored grain pests. These models verify the
benefits of aeration for suppression of pest populations (Fig. 3). Although costs of
aeration depend on local electricity costs, in most cases expenditures are justified based
on reductions in insect infestations that can be achieved (38).
Biological controls and biologically-based pesticides may provide additional nonchemical methods for pest control in stored grain. The community of insect species that
infests stored grain includes those that consume the grain itself, those that feed on molds
which infect the grain, and entomophagous parasitoids and predators. Studies have been
published in which experimental populations of grain pests have been reduced by
addition of natural enemies to storage containers (39). A recent study conducted in grain
bins has validated the efficacy of introducing parasitic wasps to suppress populations of
the lesser grain borer (40). The objective of these studies has been to identify benficial
species that can maintain pest populations at below the economic injury level (Fig. 4).
Although some companies mass produce and sell parasitoids and predators of stored grain
pests, the use of beneficial insects in grain storage facilities has not yet been widely
adopted.
(Add some additional material about basics of Bt crops here)
Genetic engineering to incorporate genes into crop plants for production of
23
24
microbial agents toxic to insects is being adopted for several major agronomic crops. The
potential is being investigated that these toxins may be present in sufficient quantities
within grain produced by these crops to control insects which feed on that grain in
storage. These toxins are not harmful to humans, and may be a valuable asset in IPM for
stored grains if they prove to be effective for post-harvest pest control.
Chemical Insecticides for Stored Grain Pests
When alternative non-chemical controls fail to maintain insect pest populations
below economic injury levels, chemical insecticides remain the most effective tools for
pest suppression in stored grain. Fumigant insecticides are ideal for bulk-stored
commodities because they are released as gases that penetrate the commodity in place.
Phosphine gas, or hydrogen phosphide, is the most commonly used fumigant for stored
grain worldwide (41). Phosphine formulated as pellets or tablets remains a relatively
inexpensive control costing a few cents per bushel (38). Phosphine is liberated from
pellets or tablets of aluminum or magnesium phosphide upon reaction with water in the
air. Because phosphine has a density close to that of air, it penetrates bulk commodities
well. It must be stated, however, that this same low density property can be a detriment
as it allows phosphine to dissipate easily if structures are not sealed well. Aluminum
phosphide pellets are typically added to grain that is being transferred from one storage
structure to another or to a transport vehicle, allowing even distribution throughout the
grain mass.
Re-circulation methods have been developed that allow adequate penetration by
the gas even when pellets are applied just to the top of a large grain mass and/or to a
bottom access via the aeration plenum. Phosphine accumulated in the headspace above
24
25
the grain is drawn through a pipe in the roof of the structure and reintroduced at the
bottom of the mass where it travels upward through the mass and attains even distribution
(42). Phosphine is relatively slow-acting and several days exposure at optimum
temperatures may be required to produce insect mortality. Long exposure time for bulk
grain is usually not a problem as considerable time is available during storage or
transport. Treatment times may be reduced by use of phosphine gas dissolved in carbon
dioxide and contained in gas cylinders now becoming available in some countries. This
formulation also provides a means for rapid, even distribution of gas througout a storage
structure.
Grain protectants are among the most commonly used controls for insects in
stored grain. These residual insecticides are applied to grain at the time it initially goes
into storage to provide protection against infestations for several months. Although more
expensive than phosphine on a per bushel basis, protectants are the preferred control if a
high risk of infestation exists. Among the disadvantages of grain protectants, as
mentioned earlier, is the potential for residues to remain in the grain at the time of sale.
Also, as the time grain is kept in storage increases, the possibility exists that the
insecticide may lose effectiveness. There is also evidence that some species are not
effectively controlled due to development of resistance to the insecticides (43).
Malathion, for example, remains a commonly used grain protectant in the United States,
though it is well established that many populations of the common stored grain insects
have evolved resistance to this compound (43). Because of these problems and the
growing expense of protectant applications, the future of this approach to control of
stored grain insects is in doubt. In addition, the use of protectants is not consistent with
25
26
principles of IPM because they are often applied with little assessment of potential pest
infestation levels. It is possible that use of insecticides as preventative measures will be
restricted to applications as residual sprays in empty structures as part of a comprehensive
sanitation program.
Diatomaceous earth is a naturally occurring absorbent dust that poses no chemical
residue or food safety problems. This material kills insects by eroding waxes from the
exoskeleton that function to seal the insect against loss of water. Death occurs due to
desiccation (44). However, diatomaceous earth is as expensive to use as synthetic
chemical insecticides, and it reduces the bulk density and the value of grain with which it
is thoroughly admixed. And, because its effectiveness is yet to be well-established, the
future contribution of diatomaceous earth to IPM in stored products is not clear.
IPM FOR FOOD PROCESSING
The information below relates to any facility in which a raw commodity such as
grain is processed in any way to make a more valuable product; such a product may be
ready for the consumer market or it may be an intermediate product that is processed
further at another facility. Thus food processing here refers to activities of flour mills,
bakeries, pet food plants, breakfast cereal manufacturers, snack food plants, chocolate
factories and confectioners.
Stored-product insects that infest food processing facilities are essentially the
same species that infest raw grain, but the species composition and their relative
importance is different. Internal grain feeding insects such as weevils and borers are not
as important in processing environments because the concern for grain damage is no
longer an issue. Species considered secondary in importance in raw grain because they
26
27
feed only on broken kernels, such as flour beetles, sawtoothed grain beetles and storage
moths such as??, are considered of primary importance in food processing because they
can easily infest milled products and contribute to problems with contaminants. For
example, the Association of Operative Millers has listed the red flour beetle as the most
important insect pest of flour mills because of its ability to survive and reproduce in flour.
This species is also difficult to control in flour mills (45). By comparison, the red flour
beetle, though common in stored grain, is rarely considered more than a nuisance. Also
important is the consideration that once grain is milled into flour, its value increases
greatly, and economic injury levels for pests decrease accordingly.
Sanitation and Prevention
27
28
Food processing facilities must devote personnel and other resources to sanitation, pest
monitoring, and pest control if they are to maintain a level of cleanliness and product
quality that is demanded by consumers and mandated by governmental regulations. As
with stored grain, preventive measures are basic to pest management programs. For flour
mills and other processing plants, the sanitation routine should include daily or twice
daily cleaning of equipment and floors where flour dust can accumulate (46). Use of
compressed air to blow dust from machines and floors is a popular cleaning tool, but it
should used used sparingly so that dust is not simply blown into hard-to-clean areas.
Food debris that accumulates in these areas can support residual populations of pests that
constantly contribute to infestation of the product. Sweeping is effective when combined
with vacuum cleaning. Problem areas for dust accumulation should be identified and
regularly targeted with vacuum cleaning. Spills need to be cleaned immediately and
broken packages discarded. Broken windows, window screens, and other structural
components should be repaired promptly to limit entry of food pests into a facility.
Rotation of raw and finished stock to utilize older products first represents a simple
preventive measure to avoid the opportunity for growth of pest populations. Common
sense approaches to sanitation and prevention need to be adopted, but in many facilities
the simple measures are overlooked in favor of increased production.
Monitoring for Pest Infestations
Active efforts at pest detection and monitoring should be incorporated into a regular
routine with sanitation and prevention efforts of food plants. Direct sampling of
products and residues from the production line can alert managers to the presence of
incipient pest problems (46). As dust and siftings from different points in the milling
28
29
process are cleaned up, these materials should be carefully inspected daily for the
presence of insects. Similarly, floor sweepings and the residue form machinery cleanouts must be inspected. Boots of elevator legs and the bottom trays of vertical conveyor
systems contain spaces where food and pests can accumulate, and should be cleaned and
inspected regularly. Insect traps baited with attractants for certain species, or designed to
capture any insects present, can be used throughout a facility to determine the presence,
relative abundance and location of pests (47). Traps baited with pheromones are highly
sensitive to the presence of the target species for the attactant. By deploying traps in a
regular grid-like arrangement throughout facilities, manager can identify areas with the
highest likelihood of insect infestation and concentrate monitoring efforts in these areas.
Monitoring data from traps or product and residue samples must be documented and the
records maintained over time, so that trends in pest numbers can be observed and utilized
in IPM decisions.
Controlling Pests (without Methyl Bromide)
29
30
Methyl bromide has been used effectively for many years to suppress pest populations in
structures such as flour mills and food processing plants, so that chronic infestation
problems have not persisted (48). Grain millers and other processors consider this
chemical to be an essential component of their pest control and sanitation programs.
Methyl bromide will be unavailable for most uses in the United States and in most other
industrialized countries beginning in the year 2005. No fumigant gas is available that can
directly replace methyl bromide for rapid, effective insect control without harmful
residues in food products. Phosphine is registered for use in structures containing food
and leaves no harmful residues on food. However, phosphine often requires several days
to achieve effective insect control, compared to several hours required with methyl
bromide. Large flour mills and similar plants continue production 7 days weekly, and can
not operate profitably with the long shut-downs that would be required for phosphine
fumigation. Another concern of many food processors when considering fumigation with
phosphine is that copper and other metal components of machinery can be corroded by
phosphine at high humidities and warm temperatures (49). Electrical wiring and sensitive
electronic equipment may be put at risk when phosphine is used in flour mills or food
processing plants. One innovative application method for phosphine as a substitute for
methyl bromide is use of relatively low doses with elevated temperatures and the addition
of carbon dioxide. This method may increase activity of the insecticide and reduce
potential damage to machines by shorter exposure times, especially in areas where
sensitive electronic equipment is housed (50, 51). The presence of carbon dioxide and
higher temperatures apparently increases respiration rates of insects and enhances
mortality.
30
31
Various other physical and chemical methods have been proposed as alternatives
to use of methyl bromide for pest control in food processing, however, none can be
considered an effective replacement in terms of efficiency and effectiveness (52).
Controlled atmospheres with high carbon dioxide or low oxygen concentrations have
been proposed but are not practical or cost-effective for food processing facilities because
of the need for enormous amounts of gases released in structures that can not be sealed
tightly. Heat treatment, or “heat sterilization”, of entire facilities has been attempted with
some success, however, for effective insect control it is necessary to maintain the
temperature at approximately 50 C for 24-36 hrs (53). A major problem with heat
treatment is the difficulty in attaining temperatures lethal to insects inside walls and
machines, and close to floors in basements.
Numerous residual insecticides have been proposed as replacements for methyl
bromide. Their effectiveness is limited, however, because they often cannot be applied in
all areas where control is needed because of risks of contamination of food products by
chemical residues. Consequently, control must be attained through residual activity on
treated surfaces where insecticide residues are not likely to contaminate food products
with the hope that insects may be controlled through contact with treated surfaces (43).
Also being evaluated in flour mills is a combination of elevated temperatures and
thorough dusting with diatomaceous earth (54). This method also has limitations for
control of insects harbored deep within structures. It seems apparent that when
registrations for methyl bromide are finally cancelled, food processing facilities will be
forced to develop more intensified efforts at prevention, vigilant monitoring, and
specialized mitigation measures to replace the current unilateral applications of methyl
31
32
bromide for pest control.
IPM FOR VALUE-ADDED FOOD PRODUCTS
At the end of the food processing continuum are the high-value, packaged products ready
for retail marketing to consumers. After leaving a processing facility, these products are
typically transported to regional wholesale distribution centers where they may be stored
for periods ranging from a few days to many months. Although ownership of these
products may reside with retail marketers, problems with pest infestations during storage
and even at retail outlets, are often blamed on the food processors. Regardless of who
takes the responsibility for protection of these products, substantial investments in
preventive measures must be made to protect finished products from infestation.
Internal corporate regulation of finished product quality must be maintained
through a system of regular inspections and business-partner accountability. As a first
step, conscientious food companies should set rigorous, internal standards and conduct
sanitation audits on their own facilities and those of suppliers to insure that their
standards and those imposed through governmental regulations are met. Sanitation
standards or specific Good Manufacturing Practices (GMPs) are sometimes specified in
supplier contracts, placing suppliers at risk of losing business should their facilities fail to
pass sanitation audits (55). All facilities should be inspected through the auditing system,
including mills, processing plants, warehouses, and retail outlets.
Companies that produce value-added products can take several measures to
prevent pest infestations through protective food packaging and even by engineering
modifications to buildings. Many types of food packaging are at risk for penetration by
insects, with those comprised of paper and cellophane being least resistant.
32
33
Polypropylene and similar polymer films provide some additional protection against
boring and chewing insects, and their resistance to penetration improves with film
thickness (56). The greatest protection is afforded by glass and metal containers. Certain
food-safe, natural insect repellents have recently been approved by EPA for use in food
packages to deter insect infestation, but the effectiveness of these agents has not been
proven.
Structural design features for production facilities, warehouses, and retail outlets
can be improved to enhance sanitation and pest control. Cracks, crevices, and other
unnecessary openings in walls and floors should be sealed. Wall to floor junctions should
be protected by concave molded tile to prevent harborage of pests, and wood-to-wood
joints should be avoided or appropriately sealed. Voids in double-wall construction
should be eliminated in new structures as they may allow accumulation of food debris and
provide excellent harborage for pests. Physical separation of raw commodity storage
areas, processing areas, and warehouses will help to prevent movement of pests from raw
grain storage to high-value processed foods. Building exteriors should be free from
vegetation, soil, and product spills. Exterior lights should not be mounted over doors or
windows, to avoid attacting insects to these openings at night. Rather, lights should be
positioned away from the building and illuminate the structure from a distance.
ADOPTING IPM: CHALLENGE AND NECESSITY
33
34
The post-harvest food industry faces serious challenges in pest management due to
attractiveness of food products to pests, greater public demands for safe, high-quality
food products, and increasing regulatory constraints on use of chemical insecticides. It is
apparent that the industry will no longer be able to rely on the ‘quick fix’ provided by
chemical pesticides such as methyl bromide. The industry must develop and adopt IPM
programs to meet consumer demands and comply with governmental regulations.
Fundamental components of the IPM programs for the food industry must include
preventing infestations wherever possible through sanitation and pest exclusion by
sealing of structures. Also, consistent monitoring programs and judicious decisionmaking to guide the use of chemical pesticides will be critical. Alternatives to chemical
pesticides, such as biological control agents must be used when possible. Thus, IPM in
the food industry will be both preventive and responsive (57).
Decision-making parameters are not as well-defined in the post-harvest food
industry as in production agriculture, but economic injury levels and economic thresholds
must be established for all key pests. Adoption of IPM practices is being encouraged
through incentives at various levels in the industry. Some retailers are putting IPM
labelling on products and report a favorable public response to these products. A positive
public perception of IPM coupled with a desire to reduce pesticide inputs is giving
momentum to the drive for adoption of IPM.
Need some additional explanation here.....Despite adoption of IPM, there are
many unknowns regarding the safety and quality of the food supply with fewer pesticide
inputs. Increased adoption of HACCP?? and ISO-9000 protocols?? will facilitate coadoption of IPM for insect pests and should help ensure safety and quality.
34
35
BIBLIOGRAPHY
1.
C. O. Knowles, “The Pesticide Revolution,” Proceedings of Pesticides: Risks,
Management, Alternatives, Virginia Polytechnic and State University, Blacksburg,
VA, 1988.
2.
C. M. Benbrook, “Pest Management at the Crossroads,” Consumers Union,
Yonkers, NY, 1996.
3.
D. J. Sissons and G. M. Teiling, “Agricultural Chemicals,” in S. R. Tannenbaum,
ed., Nutritional and Safety Aspects of Food Processing, Marcel Dekker, Inc., New
York, 1979.
4.
G. F. Stewart and M. A. Amerine, Introduction to Food Science and Technology,
Academic Press, Orlando, FL, 1973.
5.
G. W. Ware and J. P. McMullum, Producing Vegetable Crops, The Interstate
Printers and Publishers, Inc., Danville, IL, 1980.
6.
J. M. Luna and G. J. House, “Pest Management in Sustainable Agricultural
Systems,” in C.A. Edwards, R. Lal, P. Madden, RH. Miller, and G. House, eds.,
Sustainable Agricultural Systems, Soil and Water Conservation Society, Ankeny,
IA, 1990.
7.
R. Frisbee and J. Magaro, “IPM in the Southwest,” in Proceedings of the
American Chemical Society Meeting, Point Clear, GA, 1989.
8.
E. G. Rajotte, R. F. Kazmierczak, G. W. Norton, M. T. Lambur, and W. A. Allen,
The National Evaluation of Extension’s Integrated Pest Management (IPM)
Programs, Virginia Cooperative Extension Service Publication 491-010, 1987.
9.
C. J. Scifres, “Decision-Analysis Approach to Brush Management Planning for
35
36
Integrated Range Resources Management,” Journal of Range Management 40,
482-490 (1988).
10.
National Research Council, Alternative Agriculture, National Academy Press,
Washington, DC, 1989.
11.
P. I. Szmedra, “Pesticide Use in Agriculture,” in D. Pimentel ed., Handbook of
Pest Management in Agriculture, Vol. 1, CRC Press, Boca Raton, FL, 1991.
12.
W. H. Luckmann and R. L. Metcalf, “The Pest Management Concept,” in R. L.
Metcalf and W. H. Luckmann, eds., Introduction to Insect Pest Management,
John Wiley & Sons, Inc., New York, 1982.
13.
B. Croft, “Pesticide Effects on Arthropod Natural Enemies: A Database
Summary,” Chapter 2, Arthropod Biological Control Agents and Pesticides,
John Wiley and Sons, Inc., 1990.
14.
National Academy of Sciences, Pesticide Resistance. Strategies and Tactics
for Management, National Academy Press, Washington, DC, 1986.
15.
R. Carson, Silent Spring, Fawcett, Greenwich, CT, 1962.
16.
Anonymous, Residues in Food-1988, Food and Drug Administration,
Washington, DC, 1988.
17.
R. Levins, “Perspectives in Integrated Pest Management: From an Industrial to an
Ecological Model of Pest Management,” in M. Kogan, ed., Ecological Theory and
Integrated Pest Management Practice, John Wiley & Sons, Inc., New York, 1986.
18.
V.M. Stern, R.F. Smith, R. Vanden Bosch, and K.S. Hagen, “The Integrated
Control Concept,” Hilgardia 29, 81-101 (1959).
19.
B.A. Croft, “Integrated Pest Management–The Agricultural Rationale,” in R.E.
36
37
Frisbee and P.L. Adkisson, eds., Integrated Pest Management on Major
Agricultural Systems, Texas A&M University, College Station, TX, 1985
4.
20.
Jayas, D. S., N. D. G. White and W. Muir (eds.). 1995. Stored Grain Ecosystmes.
Marcel Dekker, Inc. New York. 757 p.
Phillips, J. K. and W. E. Burkholder. 1984.
Snelson, J.T. 1987. Grain Protectants. ACIAR Monograph No. 3. Canberra. 448 p.
Keith, L. 1997. Environmentla Endocrine Disruptors: A Handbook of Porperty Data.
John Wiley and Sons. New York. 1232 p.
Price, N. 1996.
Kenkel, P., G. Cuperus, T. Phillips, R. Noyes and J. Criswell. 1997. Biological
preservation of grain quality: losses in storage and handling. Pp. 385-389 In:
Steele, J. L. and O. K. Chung, eds., “Proceedings of the International Wheat
Quality Conference,” Grain Industry Alliance, Mahattan, KS.
Stark, J. 1994.
Armstrong, J. W. 1994.
Nation, J. L. and A. Burditt. 1994.
Hallman, G. J. 1994. Controlled atmospheres. pp. 121-138, In Paull, R. E. and
Armstrong, J. W., eds. Insect Pests and Fresh Horticultural Products. CABI
International. Wallingford, UK.
Hagstrum et al. 1996
Fields, P. 1992.
37
38
Cuperus, G. W. and R. C. Berberet. 1994. Training specialists in sampling procedures.
Pp. 669-681. In: Handbook of Sampling Methods for Arthropods in Agriculture.
CRC Press. Boca Raton. Xxxp.
Subramanyam, B. and D. Hagstrum. 1996
Walter, V. 1991. Fumigation in the food industry. pp. 441-457 In Gorham, J. R., ed.
Ecology and Management of Food Industry Pests. FDA Technical Bulletin 4.
Association of Official Analytical Chemists. Arlington, VA.
Noyes. R. T. and P. Kenkel. 1994. Closed loop fumigation systems in the south-western
United States. Pp. 335-341. In Highley, E., Wright, E. J., Champ, B. R., and
Banks, H. J., (eds.). Proceedings of the Sixth International Working Conference
on Stored-Product Protection. CABI Press. Canberra.
Kenkel, P., J. T. Criswell, G .W. Cuperus, R. T. Noyes, K. Anderson, W. S. Fargo, K.
Shelton, W. P. Morrison and B. Adam. 1993. Current Management Practices and
Impact of Pesticide Loss in the Hard Red Wheat Post-harvest System. Oklahoma
Coop. Exten. Service Circular E-930.
Arthur, F. H. 1996. Grain protectants: current status and prospects for the future. J.
stored Prod. Res. 32: 293-302.
Korunic, Z. 1998. Diatomaceous earths, a group of natural insecticides. J. Stored Prod.
Res. 34: 87-97.
Noyes, R. T., G. W. Cuperus and P. Kenkel. 1994. Using controlled aeration for insect
and mould management in the south-western United States. Pp. 323-334. In
Highley, E., Wright, E. J., Champ, B. R., and Banks, H. J., (eds.). Proceedings of
the Sixth International Working Conference on Stored-Product Protection. CABI
38
39
Press. Canberra.
Browewr et al. 1996
Flinn et al. 1996
Faustini, D. L. 1990. How to use Tribolium pheromone traps. Association of Operative
Millers Bulletin. Pp. 5715-5717.
Mills, R. and J. Pederson. 1990. A Flour Mill Sanitation Manual. Eagan Press. St. Paul,
MN 156 p.
Phillips, T. W. 1997. Semiochemicals of stored-product insects: research and
applications. J. Stored Prod. 33:17-30.
Chakrabart. 1996.
Bond, E. J , T. Dumas, and S. Hobbs. 1984. Corrosion of metals by the fumigant
phosphine. J. Stored Prod. Res. 20: 57-63.
Mueller, D. K. 1994. A new method of using low levels of phosphine in combination
with heat and carbon dioxide. pp. 123-125 In Highley, E., Wright, E. J., Champ,
B. R., and Banks, H. J., (eds.). Proceedings of the Sixth International Working
Conference on Stored-Product Protection. CABI Press. Canberra.
Mueller, D. K. 1995. Low concentration phosphine fumigation method. U.S. Patent
number 5,403,597. 13 pp.
Annis and Watterhouse. 1996.
Sheppard, K. 1984.
Fields, P., A. Dowdy and M. Marcotte. 1997. Structural pest control: The use of an
enhanced diatomaceous earth product combined with heat treatment for the
39
40
control of insect pests in food processing facilities. Agriculture Canada
Publication.
Hohman. 1991
Highland, H. 1991.
Hagstrum, D. W. and P. Flinn. 1996.
(below not used yet)
National Pest Control Association. 1994. Integrated Pest Management in Retail Food
Stores. Technical Release ESPC 07210. Vienna, VA.
USDA Agricultural Marketing Service. 1997. Pesticide Data Program: Annual Summary
Calendar Year 1995. Washington, D.C.
USDA Agricultural Marketing Service. 1998a. Pesticide Data Program: Annual
Summary Calendar Year 1996. Washington, D.C.
USDA Agricultural Marketing Service. 1998b. Pesticide Data Program: Annual
Summary Calendar Year 1997. Washington, D.C.
Flinn, P., D. Hagstrum and L. Song. Stored grain advisor, an expert system for stored
grain management. Ver. 3.01. USDA ARS
45.
40
41
Table 1. Detection of Insecticide Residues in Wheat Samples from Grain Elevators in
Major Wheat-Producing States of U.S.1
Percentage of Samples with Detectable Levels in a Given Year2
Insecticide
1995
1996
1997
(600)
(340)
(623)
0.5
0.3
0.3
4.7
5.2
Carbaryl
Chlorpyrifos 19.5
14.4
6.4
Chlorpyrifos Methyl3 54.2
73.2
Dichlorvos
0
0
0
Malathion3
71.0
70.3
68.2
Methoxyhlor
Methyl Parathion
55.6
1.0
0
0.3
0.2
1
Data compiled from x y and z
2
Number in parentheses refers to the number of samples analyzed in a given year
3
Registered by U.S. Environmental Protection Agency for direct admixture to grain as a
protectant; other insecticides residues presumably resulted from other applications.
41
42
Figure Legends
Fig. 1. Survival of lesser grain borers as a function of temperature and wheat moisture
content (adapted from Hagstrum et al. 1996)
Fig. 2. Devices used to sample grain for insect population monitoring. a. A spear-shaped
grain trier to extract a sample of grain from bulk storage. b. An insect probe trap that is
inserted into a grain mass; insects moving through the grain pass through the holes in the
trap and fall into the collection tip. c. A pelican sampler used to collect a sample of
flowing grain as it falls vertically.
Fig. 3. Conceptual plot of a grain insect population size with and without aeration to cool
grain and slow population growth. ET=economic threshold; EIL=economic injury level
(adapted from Hagstrum and Flinn 1996).
Fig. 4. Conceptual diagram indicating how a pest population can be suppressed by the
introduction of a parasitoid, which is a biological control agent. PE=population
equilibrium; EIL=economic injury level; ME=modified equilibrium (adapted from
Brower et al. 1996).
42