PART I.   INTRODUCTION

Each year, insect and mite pests cause severe losses to U.S. agriculture by affecting crop yield and quality, either through direct feeding or by transmitting plant pathogens.  Modern agriculture, with its large contiguous plantings, has contributed to the situation by providing these pests with vast food sources, facilitating their rapid population growth and spread.  Although native pests are of considerable importance, rapid transportation by sea and air have broken down the geographic barriers that have historically retarded the spread of insect pests.  Consequently, many exotic invasive species have become established in the United States in recent years.  Almost always, they arrive without any of the natural enemies (parasitoids, predators, and pathogens) that attack them in their land of origin, so they are able to multiply and spread with little hindrance and become major pests over wide areas in a short time.  Unfortunately, we often know little about their biology and natural enemies at the time they are discovered, and considerable research is frequently needed before effective eradication or suppression programs can be implemented.  Free trade policies and agreements implemented in recent years appear to have increased the likelihood of such invasions, as witnessed by the discoveries of Asian longhorned beetle (Anoplophora glabripennis) in New York and Illinois; pink hibiscus mealybug (Maconellicoccus hirsutus) in California; and a soybean aphid in the Midwest.  As pressure from arthropod pests increases, agriculture faces continuing cultural pressures as well, because consumer acceptance and food quality standards prevent marketing agricultural produce blemished by insect or mite attack or containing body parts of the pest.

Because of their extreme diversity (at least one million species of insects and 50,000 species of mites), little is known about many species.  A few species of great economic importance have been studied in considerable detail, but our knowledge of others, including natural enemies, is frequently lacking.  Subtle differences in the biology or behavior of even closely related species, can make the control measures used against one species ineffective against a near relative, so detailed biological data are needed.  Difficulties in detection of these insects and mites may hinder the ability of growers to take timely action when pest populations are increasing in an agroecosystem and may also greatly increase the probability of an exotic pest entering the country through international ports of entry.  The enormous reproductive capacity of insect and mite pests contributes considerably to the damage that they cause.  Though this is one of the pest’s greatest strengths, it also represents a potential weak link that may be exploited.  In-depth studies on all phases of the reproductive process have produced technologies useful in control of many pests.  High reproductive capacity coupled with short generation times leads to rapid population growth necessitating the development of complex models, sophisticated monitoring devices, and accurate decision tools for growers, so that they may act before pest populations reach damaging levels.  Their genetic variability and short generation times permit pests to adapt rapidly to major changes in their environment.  In addition to allowing them to quickly exploit new food sources, this high adaptability has resulted in the rapid development of resistance to insecticides by over 500 pest species during the last 50 years.  Development of resistance is also a concern in the use of plants that have been genetically modified for pest resistance.  Successful management of resistance to Bt toxins will be critical to the continuing usefulness of transgenic crops containing the Bt gene.  Other aspects of basic biology such as body structure, locomotion, and protective adaptations also contribute to the difficulties inherent in arthropod pest control.  Greater knowledge of these systems must be obtained to meet the challenge that insect and mite pests present to U.S. agriculture.

Insect and mite pests have natural enemies (parasitoids, predators, and pathogens) that act to kill or to otherwise regulate their population growth.  Some natural enemies provide natural control, unknown to the grower, helping to optimize crop quality and yield in many crop systems; others are used in applied biological control programs directed at specific target pests.  The concept of integrated pest management (IPM) relies upon the premise that all existing suppressive factors in the environment should be optimized to the greatest practical extent.  However, many pests, especially exotic invasive species, have no effective natural enemies in the United States; information on the natural enemies of these species is needed.  Before a natural enemy can be used in biological control, research is needed in the following areas:  (1) basic biology, including behavior, life cycle, specificity to its host, physiology, genetics, and reproduction [see also Component I - Identification and Classification of Insects and Mites]; (2) population biology and ecology; and (3) rearing, including nutrition and culture techniques.  A better understanding of basic biology and ecology, as well as improved rearing methods, are needed for all categories of natural enemies.  Although there has been marked progress in the use of natural enemies in augmentative and classical biological control programs, their application could be greatly increased.  Future successes in the field of biological control will depend primarily on basic biological and ecological research performed on natural enemies of insect and mite pests.

 PART II.  PROBLEMS TO BE ADDRESSED

A.    Basic Biology

Problem Statement
Rationale.  Modern agriculture is evolving from a broad-spectrum chemical approach to pest control to one of integrated pest management that may include species or group-specific chemicals (i.e., semiochemicals, hormones, and new chemistries), natural enemies, genetically modified plants, sterile male techniques, mating disruption, and other cultural or physical means of pest control or prevention.  For more effective IPM strategies to be developed, fundamental in-depth knowledge of pest and natural enemy biology is needed.  Successful programs of pest suppression or eradication have relied on this information. However, such successes have been realized for but a handful of the pests that affect American agriculture.  Failure of some biological control or eradication programs, biopesticides and cultural control methods has been attributed to lack of sound specific biological knowledge about a pest or natural enemy or their interactions with the environment.  Sound biological knowledge bases are critical to the development of efficient, viable, environmentally friendly, ecologically sound, and sustainable strategies of pest control.

What is known.  Almost every crop grown in the United States is attacked by one to three major insect or mite pests and a myriad of other minor, occasional or potential pests.  For some pests, enough background data have been generated on basic biology to develop effective management approaches that have reduced the pest status of the insect in many areas.  However, most studies have been limited to local populations, even with some major pests, so that insufficient information is available to develop areawide approaches to pest management, expert systems for producers, models for release of parasitoids or predators, and/or to utilize selective chemicals or semiochemicals.  For most insect pests there are some studies on the effect of temperature, moisture, climatic or edaphic (relating to the soil) characters in a particular region on their movement, fecundity, development, physiology, overwintering habits or aspects of their biology.  However, the information may not pertain specifically to a particular species or may concern only one life stage.  Discovery of semiochemicals that were initially recognized as attractants or pheromones have led to advances in pest management and insect detection, for example, areawide suppression of corn rootworms, early detection of Japanese beetles, and mating disruption of codling moth. 

Gaps.  Many aspects of the basic biology of insect and mite plant pests and their associated natural enemies are poorly understood.  Implementation of new approaches to pest management that are environmentally sound and sustainable, requires research into the basic biology of (1) each major insect and mite pest and their natural enemies on each crop, and (2) each secondary, minor, and potential insect and mite pest and their natural enemies on each crop.  This research must consider genetic relationships within and among species and groups of species, physiology and nutrition, mating, fecundity, life tables, developmental processes as related to environmental factors, behavior of all stages, escape tactics, molecular genetics and chemical ecology.  Semiochemicals have not been studied for many pests.  Molecular markers are needed to distinguish cryptic species, track dispersal and identify geographical origins of these insects and mites. 

Goals 

• Develop an understanding of the organismal biology, behavior, chemical ecology, genetics and bionomics of major, minor, occasional and potential crop pests and their natural enemies.
• Identify key factors that influence the development and other life processes of pests and their natural enemies.
• Determine how the interactions of natural enemies and arthropod pests of crops with their environment affect the development and life processes of these organisms (also see Component III, Plant, Pest, and Natural Enemy Interactions and Ecology).

Approach 
Interdisciplinary areas of research (physiology, genetics, chemical ecology, behavior, bionomics, molecular genetics and biochemistry) will be coordinated to study insect and mite pests and their natural enemies (arthropods or microbes).  The effects of interactions among factors will be considered in relation to pest and natural enemy occurrence and pest status, and natural enemy efficacy.  Particular attention will be focused on events, behaviors, communication methods, adaptations or strategies for surviving adverse conditions, developmental thresholds, and genetic components, that may be vital links in the life processes of arthropods.  Understanding such critical links may present opportunities to develop pest management tools or may provide the insight necessary to avoid pitfalls when developing novel pest management strategies.

Outcome

• Knowledge of key factors of life processes that contribute to new and efficient methods of pest management
• Sound biological bases for use in development of environmentally-safe and ecologically-sound pest management systems      

Impact  
Pest management strategies based on biology of target pests and their natural enemies 

Linkages to Other ARS National Programs
Air Quality (203)
Crop Production (305)
Integrated Agricultural Systems (207)
Plant Biological and Molecular Processes (302)
Plant, Microbial, and Insect Genetic Resources, Genomics, and Genetic Improvement (301)
Soil Resource Management (202)
Water Quality and Management (201) 

B.    Rearing of Insects and Mites

Problem Statement
Rationale.  The ability to rear insects and mite pests is a fundamental requirement in conducting research needed to develop tools for their suppression.  In the case of biological control and suppression or eradication strategies, rearing the pests and/or their natural enemies is an essential part of the control program itself.  Since the 1960’s, great progress has been made, but many obstacles still remain.  Some well-known insect pests (e.g., Japanese beetle) still cannot be reared successfully in the laboratory, which hinders efforts to rear their natural enemies.  In addition, even for insect pests for which successful rearing methods have been developed, cost-effective rearing methods are not available for their natural enemies.  Usually, the deficiency involves meeting nutritional requirements, but there are other problems such as determination of optimal environmental conditions, synchronization of life stages, elimination of biased sex ratios, adverse effects of inbreeding and others.  Finally, once an insect or mite or natural enemy can be reared, it is necessary to conduct developmental research so that large numbers of high quality individuals can be produced economically.  In addition, strict control of insect pathogens in host rearing systems must be developed to insure quality of the species produced. 

What is known.  Basic nutritional requirements are known for some of the major groups of insects and mites.  An overall conceptual model of basic feeding biology has been established, but particulars are lacking for many pests and their natural enemies.  Artificial diets have been developed for numerous butterflies, moths, beetles, and flies, and rapid progress is being made for others such as bees, wasps, and ants; in vitro diets have been developed for some parasitoids.  Automation and mechanization are available for diet preparation.  Researchers, commercial producers, and users of mass-produced insects realize that quality, for both hosts and natural enemies, is important in the rearing process.  Diet quality is positively correlated with growth, longevity, and egg production in the insect being reared.  Complementary sex determination and microbial symbionts (e.g., Wohlbachia) are known to affect sex ratio in many parasitic bees and wasps.  Temperature and length of days and nights are known to influence incidence of diapause (i.e. a period of suspended reproduction and reduced metabolism) and its termination in many insects.  For the insects produced, it is not always clear which characteristics are the most important or how to improve them.  In vitro diets have been developed for some parasitoids.  

Gaps.  The characterization of and amelioration of inhibitory compounds in nutrient diets is poorly known, and those for many species need to be detected, identified and eliminated.  Quality control systems need to be developed, not only for the beneficial species but also for their hosts (elimination of pathogens).  In some cases, alteration or lack of an essential nutrient may adversely affect insect development.  Artificial diets for some groups with piercing-sucking mouthparts are lacking.  Strategies for eliminating male-biased sex ratios in parasitic bees and wasps used for biological control need to be developed.  Augmentation of natural enemies to increase their effectiveness in crop protection has met with mixed results and has been hindered by quality control and logistical problems.  Little is known about the genetics of most pest insects and their natural enemies, but the effects of inbreeding on laboratory colonies are believed to be deleterious.  Molecular techniques are needed for determining whether genetic bottlenecks occur in mass-rearing programs.   

Goals

• Develop insect and mite rearing systems that minimize adverse effects of inhibitory compounds in nutrient diets and contaminants, while maintaining the nutrients and environmental conditions needed to produce a quality organism, whether for research or pest suppression purposes.
• Develop production systems that permit the mass-rearing of high-quality insects and mites at a reasonable cost (for improved delivery systems see Component V - Pest Control Technologies).
• Develop new and improved artificial diets for parasitoids and predators, eliminating the need to rear large numbers of host or prey species.
• Develop protocols for quality assessment and quality control of diet ingredients, completed diets and fitness characteristics of reared arthropods. 

Approach
A multidisciplinary approach will be used to develop arthropod rearing practices that increase production efficiency, while maintaining quality of the species being reared.  The roles of nutrients, pH, gelling agents, antioxidants, antimicrobial agents, emulsifiers, purification strategies, and sterilization procedures in the dynamics of feeding, digestion and absorption will be determined.  Research in these areas will be integrated to improve the formulation and shelf-life of artificial diets.  Methodologies, such as real time imaging, will be used to automate sexing and counting arthropods in mass rearing.  Molecular techniques will be used to monitor genetic parameters in laboratory colonies started from field-collected and to make periodic comparisons of selected fitness parameters with those of insects in the field.  In-depth studies on factors affecting sex ratios of parasitic bees and wasps will be conducted.  Economically-, biologically-, and logistically-sound protocols for quality control of reared arthropods and their natural enemies will be developed through interaction with commercial insectaries and action agencies. 

Outcomes

• Rearing systems that produce healthy arthropods for research and suppression purposes
• Production systems that enhance the quality of reared insects and mites
• Improved lower-cost artificial diets that increase the possibilities for autocidal (self-destruct) and augmentative (supplemented) biological control strategies in pest suppression programs 

Impact
Improved research and control of insect and mite pests

Linkages to Other ARS National Programs
Crop Production (305)
Integrated Agricultural Systems (207)
Plant, Microbial, and Insect Genetic Resources, Genomics, and Genetic Improvement (301)