ndFor the Encyclopedia of Food Science and Technology, 2 Edition
POST-HARVEST INTEGRATED PEST MANAGEMENT
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
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
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 post- harvest 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 decision-making 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
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 cost-efficient 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.
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 bio-intensive 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
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.
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. 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
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).
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