INSECT MANAGEMENT ECOLOGY
Joseph L. Spencer and Eli Levine
At any given moment, we share this planet with a billion living insects having a total mass equivalent to that of the entire human population. We interact little with the vast majority of insect species, many of which provide valuable benefits in the form of pollination services, recycling dead plant and animal tissue, and predation on pest species. Insects also serve as food for animals (and humans), are subjects of scientific research, and have considerable aesthetic value. Though the benefits of insects (estimated at nearly $20 billion per year in the United States) exceed the losses (at about $5 billion per year) caused by the few insect species (2%-5%) classified as pests, we cannot ignore the substantial threat they pose to our health, food supply, and fiber production.
At its founding in 1858, the Illinois Natural History Survey was given the mandate by the State of Illinois to conduct research on economically important insects and provide recommendations for the control of harmful species. The University of Illinois' agricultural college has largely depended on the Illinois Natural History Survey to conduct research for the agricultural community and distribute its findings to the public and our policymakers. Since our beginning, the Survey's research scientists, extension specialists, and support personnel have provided timely guidance to constituents faced with the appearance of new insect problems and changes in the behavior of existing pests.
With an agricultural landscape increasingly shaped by market forces and the needs of a burgeoning human population, our inventory of pest control options has evolved with the revolutions in agriculture. During the last century, humans have employed a succession of suppression and control tactics to alleviate pest problems with insects, mites, plant-parasitic nematodes, bacterial, fungal, and viral plant pathogens, weeds, and vertebrate animals. Perhaps no stratagem was hailed with more enthusiasm (and later decried with greater scorn) than the synthetic organic insecticide revolution that began in the 1930s.
By relying on repeated chemical applications as the sole tactic to control
pests, farms and farmlands
became laboratories for the evolution of insect resistance to insecticides. Some of these insecticides gradually lost effectiveness because the few individuals who happened to be genetically resistant to them survived and reproduced, and soon whole populations possessed the same resistance. Overuse of insecticides during this period inaugurated exponential growth in the tally of insecticide-resistant insect species and is, unfortunately, a lasting legacy of the chemical era. Indiscriminate use of broadly toxic and persistent insecticides also resulted in contamination of the environment with pesticide residues and the death of nontarget organisms and the natural enemies of pest species. Free of natural enemies, pest population densities after insecticide treatment often exceeded those before pesticide treatment. The greatest percentage of pest problems occurred in agricultural production systems, where vast monocultures of susceptible hosts were grown over large areas. Lacking the diversity that buffers natural ecosystems, these systems were especially vulnerable to perturbation.
INHS
researcher Joe Spencer
observing
corn rootworm behavior.
Publication of Rachel Carson's Silent Spring in 1962 was a catalyst for public concern over the accumulating ecosystem-wide effects of more than two decades of unilateral chemical control. By the 1970s, acknowledgment that the nearly exclusive chemical approach to pest control was at variance with ecosystem health, tempered with the realization that insecticides were essential for insect control, lead to a more ecologically based approach to pest control known as integrated pest management, or IPM. The primary goal of IPM is the reduction of losses due to pests in ways that are not only effective, but also economically sound and environmentally compatible. Long-term solutions to problems rather than just short-term protection from pests is an important goal of IPM; reducing or modifying the impact of pests and reducing injury to tolerable levels is of greater concern than simply killing pests.
Frequently associated with crop protection, the scope of IPM is much broader, encompassing pest problems with livestock and pets, urban dwellings, ornamental plants, and medically important pests, such as mosquitoes and ticks, which may cause discomfort and act as vectors of human disease. Within IPM, several techniques are often used simultaneously to solve a specific pest problem. For example, a pest management program may employ the use of natural enemies, resistant varieties, crop rotation, tillage, sanitation, and other advancements to keep pest populations below levels that cause economic damage (economic threshold). Although pesticides may be used in some specific cases, IPM practitioners weigh the needs and alternatives to these chemicals before choosing an approach. Effective tailoring of a management approach depends on identifying the pest that is causing the problem and a thorough understanding of the pest's biology and its relationship to the host and the environment. IPM also requires an assessment of pest status, which is usually determined by sampling for pests and measuring levels of pest injury. Around the world, IPM has become the pest control paradigm of choice for agriculture. In 1993, the Clinton administration called for its adoption on 75% of U.S. farmland by the year 2000.
The Future of Pest Control
IPM and the pest situation are constantly changing. The 1990s witnessed a revolution in plant biotechnology that has provided growers with an ever-expanding selection of plant varieties that may be incorporated into an existing IPM program. The availability of plants that produce narrowly specific toxins which target particular pests species reduces the need for pesticide applications and lessens the impact of pest management on nontarget organisms and the environment. Whereas the hard lesson of pest resistance was learned only belatedly during the chemical revolution, today's scientists are developing strategies for the deployment of new genetically engineered plants before their commercialization so that rapid evolution of pest resistance may be avoided. Recognition that a pest's susceptibility to a control constitutes a precious commodity is transforming the way IPM is applied. The tremendous development costs and potential benefits of transgenic plants warrant that extraordinary attention be directed in the use and stewardship of these products.
A climate of regulatory reform has sharpened our focus on perfecting new insect control modalities and preserving the demonstrated utility of our existing tools. Under the Food Quality and Protection Act (FQPA), the use of some compounds that were chemical mainstays of IPM programs will be restricted or eliminated in the near future.
Transgenic crops and other alternatives to traditional chemical control, such as host-plant resistance, will figure prominently in the future of insect pest management, as will the need to view insects as parts of an integrated system.
As a leading agricultural state, Illinois is at the forefront of innovation in crop production and pest management. Active research programs at the Illinois Natural History Survey are essential for improving current IPM systems and solving new problems as they arise. The western corn rootworm is a case in point. Until recently, western corn rootworm beetles laid their eggs almost exclusively in cornfields. Since rootworm larvae can only survive if they feed on the roots of corn, planting soybeans (a nonhost plant) in a field that was previously infested with eggs broke the rootworm life cycle. Likewise, corn planted after soybeans contained few eggs and no insecticide was needed to protect the crop from rootworms. Annual rotation of corn and soybeans exploited biological constraints on adult and larval rootworm development and formed the basis of a simple but effective IPM system for preventing western corn rootworm injury to corn without the need to use a soil insecticide. However, all that changed in 1993 when Survey scientists discovered that western corn rootworms were beginning to lay eggs in soybean fields. By 1995, widespread injury to rotated corn in nine east-central Illinois counties forced many corn producers to use a soil insecticide on their first-year corn acreage for the first time.
Scott Isard
collecting
western corn rootworms from Malaise
traps.
In response to this change in egg-laying behavior, Illinois researchers
developed sampling procedures (yellow sticky traps) and a preliminary economic
threshold for western corn rootworm beetles in soybean fields. This will allow
farmers to make informed decisions on the need for a soil insecticide in
first-year corn on a field-by-field basis. Fields with fewer than the
threshold number of beetles (seven beetles per trap per day) would not need to
be treated with a soil insecticide when rotated back to corn the following
spring. The need to better understand the change in egg-laying behavior also
led to a detailed study of its possible mechanisms and the role the shifting
spatial and temporal distribution of host and nonhost played in the evolution
of behavioral resistance to crop rotation.
Expertise of Survey scientists along with the findings generated from their research programs will also feature prominently in the design of IPM and Insect Resistance Management (IRM) programs for the imminent deployment of transgenic corn that will specifically target the corn rootworm. Other Survey scientists continue to play prominent roles in the development of models for evaluating the likely outcomes of using genetically engineered crops against major insect pests like the European corn borer. These simulation models rely on accurate and detailed information about pest biology and ecology. Biologically based models offer Survey scientists a venue to explore, among other things, the resistance potential of control programs with the goal to develop resistance management strategies which prolong the life span of newly developed genetically engineered crops such as Bt corn for European corn borers.
The research of other INHS scientists involves development and refinement of IPM strategies to manage additional pest species from increasingly complicated agricultural, urban, and natural landscapes. Examples of these strategies include strip tillage and intercropping to improve vegetable production; evaluation of microbial pesticides, plant-based insecticides, and resistant or tolerant crop varieties; and using natural enemies to control serious weeds, such as purple loosestrife, that reduce the diversity of aquatic ecosystems.
INHS RESEARCH PROJECTS ON INSECT MANAGEMENT ECOLOGY
*Reduced tillage and cover crop mulches: effects on weed, insect, and
disease
problems in vegetable cropping systems
C. Eastman, J. Masiunas (U of I), K. Amisi
*Insect/weed/vegetable crop interactions
C. Eastman, J. Masiunas (U of I), J. Aguyoh
*Alternative broccoli pest management systems using glucosinolate-rich
cultivars
and mulches
C. Eastman, J. Masiunas (U of I), M. Kushad (U of I), C. Velasquez
Damage to cabbage leaves caused by caterpillars.
*Interchange of biota between agricultural and wild systems
M. Irwin, G. Kampmeier
*Plant virus epidemiology
M. Irwin, G. Kampmeier
*Aphid migration and movement
M. Irwin, G. Kampmeier
*International crop protection and soybean pest management
M. Irwin
*Biological database development
G. Kampmeier, B. Heidorn (U of I)
*Population densities of western corn rootworm beetles and egg-laying in
different soybean lines
E. Levine, J. Spencer, M. Gray (U of I), R. Nelson
*Seasonal movement of western corn rootworm beetles from corn into soybean
fields at five locations in Illinois (Urbana, DeKalb, Dixon Springs, Monmouth,
and Perry)
E. Levine, J. Spencer, L. Paul, R. Hines, E. Adee, G. Raines
*Genetic differences between western corn rootworms that lay eggs in corn
and
those that lay eggs outside of cornfields
T. Clark (University of Nebraska), E. Levine, J. Spencer
*Greenhouse insect pest insecticide efficacy
P. Nixon, L. Hanks (U of I)
*Biology and management of turfgrass insect pests
P. Nixon
*Efficacy of insecticides to control alfalfa weevil larva in southern
Illinois
J. Shaw, J. Finger, E. Armbrust
*Efficacy of insecticides to control potato leafhoppers in alfalfa
J. Shaw, J. Finger, E. Armbrust
*Efficacy of pre-plant, planting-time, pre-emergence, and rescue
insecticide
treatments for black cutworm control in Illinois
J. Shaw, J. Finger, M. Gray (U of I), K. Steffey (U of I)
*Efficacy of registered and experimental insecticides to control corn
rootworm
larvae in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of different formulations of Regent applied at planting to
control
corn rootworm larvae and first-generation European corn borer in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of different formulations of the soil insecticide Chlorpyifos
against
corn rootworm larvae in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of seven different seed treatments for control of corn rootworm
larvae
in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of registered and experimental insecticides for control of
first-generation European corn borer in Illinois
J. Shaw, K. Steffey (U of I), M. Gray (U of I), J. Finger
*Efficacy of registered and experimental insecticides for control of
second-generation European corn borer in Illinois
J. Shaw, K. Steffey (U of I), M. Gray (U of I), J. Finger
*The effectiveness of Bt-corn hybrids for control of European corn borer
in
Illinois
J. Shaw, K. Steffey (U of I), M. Gray (U of I), J. Finger
*Evaluation of efficacy of selected conventional and experimental
insecticides
and Bt hybrids for control of corn earworm and European corn borer on sweet
corn in Illinois
J. Shaw, R. Weinzierl (U of I), J. Finger
*Evaluation of efficacy of selected conventional and experimental
insecticides
for control of European corn borer on snap beans in Illinois
J. Shaw, R. Weinzierl (U of I), J. Finger
*Insecticide evaluations for control of lepidopteran and aphid pests of
cabbage
in Illinois
J. Shaw, C. Eastman, J. Finger
*Evaluation of DuPont MP-062 WG and Confirm 2F for control of codling moth
and
other direct pests of apples in Illinois
R. Weinzierl (U of I), J. Shaw, J. Finger, M. Hurt
*Efficacy of registered and experimental insecticides to control corn
rootworm
larvae in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of different formulations of the soil insecticide Chlorpyifos
against
corn rootworm larvae in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of seven different seed treatments for control of corn rootworm
larvae
in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of registered and experimental insecticides to control corn
rootworm
larvae in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Efficacy of seven different seed treatments for control of corn rootworm
larvae
in Illinois
J. Shaw, M. Gray (U of I), K. Steffey (U of I), J. Finger
*Insect pathogen interactions
L. Solter, D. Pilarska (Bulgarian Academy of Sciences)
*New technology for studies of microsporidia
L. Solter, J. Vavra
*Host specificity of insect pathogens
L. Solter, J. Maddox
*Collection of viable microsporidian spores
L. Solter, J. Maddox
*Movement and mating of adult western corn rootworms in east-central
Illinois
cornfields
J. Spencer, D. Onstad, E. Levine, S. Isard (U of I)
*Aerial movement of western corn rootworms into Illinois soybean
fields
S. Isard (U of I), J. Spencer, E. Levine
*Developing strategies to manage the new western corn rootworm strain in
Illinois
M. Gray (U of I), E. Levine, J. Spencer, S. Isard (U of I), D. Onstad, R.
Nelson, M. Berenbaum (U of I)
*Survey of corn rootworms in Illinois soybean fields
J. Spencer, S. Isard (U of I), E. Levine
*Spread of western corn rootworms infesting soybeans
D. Onstad, J. Spencer, S. Isard (U of I), E. Levine
*Consumption of soybean foliage reduces vigor of adult western corn
rootworms
J. Spencer, S. Isard (U of I), E. Levine
*Daily patterns of western corn rootworm flight between corn and soybean
fields
J. Spencer, S. Isard (U of I), E. Levine
*Effect of western corn rootworm diet and diet-mixing on flight in a wind
tunnel
J. Spencer, S. Isard (U of I), E. Levine
*Characterization of substrate features important to western corn rootworm
egg-laying
J. Spencer
*Characterization of western corn rootworm egg-laying behavior
J. Spencer
*Effects of insecticide application and transgenic corn on soil
invertebrates
and soil processes
E. Zaborski, L. Soeken, J. Shaw, M. Gray (U of I)
*Development of pest control strategies for forage alfalfa persistence
E. Zaborski, G. Bollero, E. Armbrust