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CENTER FOR ECONOMIC ENTOMOLOGY

Description --- Public Service --- Special Recognition --- Project Summaries

Illinois is constantly threatened by the appearance of new insect pests as well as changes in the behavior of existing pests that produce new and different problems. Survey entomologists are often required to address these issues in a timely manner. Such was the case last year with a change in corn rootworm behavior in corn and soybean fields. The Center provides many educational programs and opportunities in cooperation with the University's Agricultural Experiment Station and Cooperative Extension Service to provide up-to-date information on the management of insect pests of agricultural, horticultural, forest, and urban environments and on the control of mosquitoes and other medically important arthropods. Reduced environmental and health hazards associated with the use of insecticides is a major component of the Center's programs.

Center extension affiliates, in cooperation with Survey entomologists and University of Illinois specialists from other disciplines, produce newsletters to provide the agricultural community with information related to current and emerging crop and livestock protection problems and give homeowners and landscape professionals up-to-date management techniques for home and garden pest problems.

Another important service of the Center is its series of educational programs that provide a learning experience for children. For example, Insect Theatre provides a series of plays, sketches, and skits to teach young audiences about insects and biodiversity. For more mature audiences, the Center staff have made numerous presentations at professional scientific meetings, museums, public and private organizations, and the College of Agricultural, Consumer and Environmental Sciences' Open House, Agronomy Day, and Insect Expo.

National leadership in entomology has characterized our Center for several years. Its members are appointed to editorial boards of prestigious scientific journals, hold elected positions within the Entomological Society of America and the American Mosquito Control Association, and serve as representatives to numerous North Central Regional Research Committees and U.S. Department of Agriculture planning committees at the national level. Staff expertise is often called upon for manuscript and grant review for the National Science Foundation, U.S. Department of Agriculture, U.S. Forest Service, and the Cooperative States Research Service.

Each year Center scientists and extension specialists, cooperating with scientists in the Center for Biodiversity, perform a time-consuming but much-needed public service-the identification of insects and other arthropods for individuals and for a variety of projects involving entomology. Economically important insect pests and potential pests must, for obvious reasons, be accurately identified. The Survey has one of the largest and most important insect collections in the United States. These collections, and the Survey's scientists who identify and classify insects, are invaluable.

Members of the Center for Economic Entomology strive for excellence in all aspects of their work. Recognition for special professional achievement is often granted by peers. Dr. Robert Novak has been elected President of the American Mosquito Control Association, Dr. Kevin Steffey is President-elect of the North Central Entomological Society of America, and Drs. Michael Gray and Richard Weinzierl are members of the executive committee of that Society. Expertise is often recognized by appointed or elected positions on special committees. Drs. Catherine Eastman, Michael Irwin, Eli Levine, William Ruesink, Richard Weinzierl, Robert Wiedenmann, the Center Director, and many of the Center's support staff hold appointments in various national organizations. The Center Director received the Alpha Gamma Rho, University of California-Davis Hall of Fame Award.

Excellence in research is often recognized by successfully obtaining competitive grants from external funding agencies. Center staff have been awarded numerous awards from the National Science Foundation, Consortium for Food and Agricultural Research, Illinois Soybean Program Operating Board, and the U.S. Department of Agriculture. Many other agencies and the agribusiness community have provided resources to support our programs. Support of this nature is vital to the continuation of the Center's research and outreach activities in fundamental and applied entomology.

Project Summaries
Pest Management --- Taxonomy - Systematics - Identifications --- Biology and Ecology --- Surveys

Pest Management

Cover crop mulches for vegetable crops
C. Eastman, J. Masiunas, H. Bottenberg, D. Eastburn (University of Illinois)
Use of cover crops could reduce soil loss and control weeds in vegetable systems. A 1995 interdisciplinary study compared the effect of conventional tillage versus reduced tillage plus mulches of rye, rye and clover, or excelsior on incidence of weeds, insects, and pathogens in two vegetable crops. Cabbage in rye mulch had fewer insect pests but yielded less than in conventional tillage. Rye mulch had a variable impact on insects in snapbean, with lower populations of pests such as potato leafhoppers and thrips. Research on fertility management and reduced soil compaction is needed to make yields more competitive in reduced-till systems.

Control of cabbage pests
J. Shaw, C. Eastman
Experimental insecticides were rated for control of aphids and larvae of the diamondback moth, imported cabbageworm, and cabbage looper in late-crop cabbage. Caterpillar numbers were moderate to low, with cabbage looper larvae the most common pest. All products reduced numbers of diamondbacks and imported cabbageworms below those in untreated plots, but only the commercial product Warrior 1EC was effective against loopers. Numbers of aphids and thrips were low all season. Experimental and commercial products were equally effective for aphid control. These evaluations are part of a program that provides impartial evaluations of pesticides for potential use on Illinois vegetables.

Biological control of purple loosestrife
R. Wiedenmann, D. Voegtlin
This project includes applied research to help solve the problems with purple loosestrife in northern Illinois by optimizing rearing and releasing leaf beetles to control this exotic weed. Because the beetles have an obligate overwintering period, Survey researchers are determining how best to overwinter adult beetles in the refrigerator, how to put them into and out of diapause, and how varying overwintering times and conditions affect survival and egg laying. Researchers also are releasing beetles in 30 locations in northern Illinois. As of May, approximately 50,000 beetles have been released at 12 sites in 1996.

Host-parasite associations of stemborers
R. Wiedenmann
This project is determining how to use novel-association parasites safely and effectively for biological control of stemborer pests. Researchers have found that three closely related parasite species each have different plant habitats they prefer, and plant habitats they definitely avoid. Also, researchers have shown that physiological compatibility differs among the three parasite species when they attack several different pest species. These results show that each species will restrict the kinds of host species encountered and attacked successfully, meaning that the parasites can be used safely with little possibility of harming nontarget species.

Biological control using Orius insidiosus
C. Armer, R. Wiedenmann, M. Irwin
Orius insidiosus is a predaceous insect that also feeds on plants. Researchers have found that Orius feeds in selected tissues of soybean plants, telling us the kinds of nutritional benefits the predator gains from plant feeding. Also, the insect must feed on prey in order to produce eggs. When prey is scarce, this predator feeds on plants, using plant nutrients to supplement its diet. Experiments using different strains of virus-infected soybean have shown slight differences in the insect's survival and fecundity among plants infected with different virus strains. Results suggest using less-serious viral strains to inoculate against virulent strains does not negatively affect this predaceous bug, thus helping conserve this important predator in soybeans.

Insecticide evaluation of crops
J. Shaw, M. Gray, K. Steffey, R. Weinzierl, C. Eastman
Field trials were conducted to provide an impartial evaluation of chemical and biological pesticides applied against the major insect pests for a variety of field, forage, and vegetable crops at several locations in Illinois. Resistant or tolerant crop varieties and genetically engineered corn varieties were assessed for efficacy of the major insect pests of their respective crops. All trials generated meaningful data to support current Integrated Pest Management (IPM) recommendations and the development of new IPM approaches.

Sources of insect resistance in soybeans
C. Helm, R. Nelson (University of Illinois)
Field and laboratory evaluations of 1,200 primitive soybean lines from China for new sources of insect resistance have identified seven lines with promising levels of leaf-feeding resistance. Further studies and crosses with existing varieties may help expand the genetic diversity of soybean, simultaneously improving yield and offering resistance to leaf-feeding insects; however, insect resistance is only part of the development of genetically improved soybean. A team of scientists from the Survey, University of Illinois, and USDA Soybean Germplasm Collection is also evaluating these primitive lines for other traits that could be used directly to improve soybean varieties.

Alfalfa weevil management
E. Armbrust, S. Roberts
A three-year study was initiated in 1995 to compare alfalfa weevil management practices and determine the impact of scheduled livestock grazing on weevil management and forage production. Management practices include a spring spray for alfalfa weevil control, fall grazing of alfalfa, early spring alfalfa harvest, spring grazing of alfalfa, late winter/early spring burning of alfalfa, early spring pyrethroid treatment, and fall harvest of alfalfa after the first killing frost. Monitoring of the alfalfa weevil's life stages, predators, parasites, and pathogens provides the optimum control strategy in a production system that includes controlled grazing of livestock.

Pathogens for control of gypsy moth
J. Maddox, L. Solter, M. Jeffords, D. Onstad, M. McManus
The gypsy moth is an established nonindigenous pest in North America. As is the case with many nonindigenous pests, gypsy moth populations in North America do not have the full complement of natural enemies that are important control agents in its native range. Eurasian gypsy moths are being examined for the presence of naturally occurring pathogens. Researchers have isolated at least six species of microsporidia, an important phylum of insect pathogens, from gypsy moths collected in Portugal, Czech Republic, Slovak Republic, Romania, Austria, and Bulgaria. The characteristics and suitability of these microsporidia as classical biological control agents are being examined.

Efficacy of current tire treatments
J. Siegel, R. Novak, R. Cieslik, J. Clarke III
One of the concerns in any tire treatment scheme for controlling mosquitoes is what percentage of the pesticide applied reaches the tires. With cooperators from the City of Chicago Department of Health and Clarke Outdoor Spray Company, a tire yard in Chicago was treated with blank granules. The number of granules per tire was counted and percent coverage was calculated. Three methods of stacking tires were evaluated: random, shingle-stacked, and column-stacked. Granule penetration was highest in the random-stacked piles and lowest in the column-stacked tire pile. Overall, between 10 and 20% of the granules actually reached their target.

Taxonomy - Systematics - Identifications

A world monograph of the Therevidae
M. Irwin, B. Wiegmann (North Carolina State University), D. Yeates (University of Queensland, Australia), G. Kampmeier, D. Webb
Researchers at the Survey, the University of Illinois, North Carolina State University, and the University of Queensland are bringing together and expanding the world knowledge of a group of predaceous flies (Diptera: Therevidae). Stiletto flies are poorly known, yet are indicators of habitat health in fragile, sandy environments. They are also biological control agents of root-feeding insects. Databases have been created to catalog the thousands of specimens from museums around the world. Stiletto flies now have a home page on the Web: http://www.inhs.uiuc.edu/cee/wwwtest/therevid/stiletto_fly.html

Asian tiger mosquito infests St. Louis
S. Hanson, R. Novak, R. Lampman, J. McDougal (Missouri Botanical Garden)
In the summer of 1994, the climatron (an indoor area similar to a greenhouse for displaying plants) at the Missouri Botanical Garden in St. Louis became infested with Aedes albopictus, the Asian tiger mosquito. The garden is visited and financially supported by many citizens of Illinois. A. albopictus was found in treeholes, bromeliads, and rock pools. Toxorhynchites amboinensis, a nonbiting mosquito whose larvae eat the larvae of other mosquitoes, has been released in the climatron to control Ae. albopictus. Bacillus thuringensis, a bacteria that kills mosquito larvae, has also been used to control A. albopictus in the climatron.

Revision of the genus Ozodiceromyia
S. Gaimari, M. Irwin
The genus Ozodiceromyia (Diptera: Therevidae) contains numerous Nearctic and northern Neotropical species. As larvae, these flies are subterranean predators of larval insects, such as beetle grubs. They are important predators in this habitat, and may be useful in assessing health of dry, friable soil habitats. This genus is poorly understood taxonomically, despite its abundance in agricultural habitats. Survey researchers are seeking a better understanding of the genus and its relationships with other therevid genera, as well as relationships within the genus. A full phylogenetic and biogeographic revision is under way, using traditional adult taxonomy, life history information, and molecular systematic techniques.

Systematics of the Chamaemyiidae
S. Gaimari, M. Irwin
Chamaemyiid larvae (Diptera: Chamaemyiidae) are predators of soft-bodied homopterans, such as aphids, scales, and mealybugs. Despite their potential importance as predators of these insects, they are poorly known taxonomically. Survey researchers are studying several aspects of this predaceous family, including nomenclatural status, revisions of several poorly understood and understudied genera, and descriptions of several new genera. Several papers are currently in review and in press on the life history and morphology of chamaemyiids. Survey researchers are also considering the systematic relationships within the family, using adult and immature morphological characters, life history information, and molecular techniques.

Revision of the genus Brachylinga
M. Metz, M. Irwin
The New World stiletto fly genus Brachylinga (Diptera: Therevidae) currently contains 16 described species. Original descriptions are ambiguous, and analyses of morphological characters appear to split the genus currently known as Brachylinga into multiple genera. As immatures, these flies, found in loose, sandy soils, are subterranean predators of larval insects such as beetle grubs, and may contribute to the natural control of several agricultural pests. Unfortunately, we know little about their bioecology or ecological impact. A phylogenetic and biogeographic revision of the genus, using adult morphology, life history information, and molecular systematic techniques, is under way.

Biology and taxonomy of microsporidia
J. Maddox, M. Baker, C. Vossbrinck, L. Solter
The Phylum Microsporida is a group of obligate pathogens infecting many groups of animals, primarily arthropods. Microsporidia are often important natural control agents of insects and may influence their population cycles. Most species of microsporidia are undescribed and the phylogenetic relationships between genera are poorly known. Using life cycle characteristics, ultrastructural features, and rRNA sequences, we are describing new species of microsporidia and evaluating the taxonomic importance of traditional morphological and ultrastructural characters.

Analysis of mosquito ribosomal (r) DNA
M. Vodkin, B. Debrunner-Vossbrinck, R. Novak
Members of the Culex pipiens complex have been reported to vector the St. Louis encephalitis virus. However, it is not possible to distinguish species of this group from field-collected samples and thus to make inferences on vector capability. Insect-specific primers were designed to amplify (via the polymerase chain reaction) the variable ITS region. All members of the complex could be distinguished after restriction digestion of the amplified product. Even geographic isolates within the same species had a characteristic pattern. Because a single leg sufficed for this assay, the rest of the mosquito is available for genetic or viral analysis.

Biology and Ecology

The movement of apterous aphids
H. Zhang, M. Irwin
Nonflight movement of aphids under a number of direct and indirect perturbations was studied in a greenhouse environment. Under crowded conditions, aphids relocated at a significantly higher rate than for any other single perturbation. When two or more perturbations were combined, aphid movement patterns were altered but the number of aphids that moved was not. Aphids move an average of three to four plants (about 13-20 cm) from the plant they originally colonized. When analyzing aphid crowding using a computer model, movement was found to be directed away from the center of crowding.

Death march and brain infection
D. Guyot, J. Maddox, M. Irwin, W. Ruesink
Baculoviruses are used as insecticides for pests in corn, soybeans, and other crops, yet, little is understood about how these viruses move in the environment. The "death march" behavior triggered by the virus before it kills the caterpillar may explain rapid dispersal of the virus in an agro-ecosystem. Researchers tested the hypothesis that this behavior is induced by infection of insect brains. A molecular genetic technique developed at the University of California at Berkeley allowed researchers to visualize individual and clusters of infected cells in insect brains. No correlation was found between brain infection and induction of death march behavior.

Western corn rootworm damage
E. Levine
Reports of severe damage to first-year corn following soybeans by corn rootworm larvae increased dramatically in Illinois in 1995. Larvae collected in damaged cornfields and reared to the adult stage were all western species. Soil samples taken in October from soybean fields that were adjacent to injured cornfields revealed that significant egg laying was taking place. No viable eggs were present in earlier soil samples taken in July. This confirms researchers' beliefs that the problem is being caused by eggs that are laid in soybean fields rather than eggs that prolong their diapause.

Rootworm egg-laying preferences
E. Levine
Cage studies with western corn rootworm beetles from problem fields in Illinois and beetles from nonproblem areas in Nebraska were conducted in a greenhouse. Beetles from Nebraska were used because of the heavy concentration of continuous corn in that area. When given a choice between mature corn and soybean plants, western corn rootworm beetles from Illinois laid a significantly greater percentage of their eggs in the soil of the soybean plants than beetles from Nebraska. Researchers believe that intense crop rotation in Illinois may have selected for a strain of western corn rootworm that lays eggs in soybean fields.

Prolonged diapause in rootworms
E. Levine
Prolonged diapause allows northern corn rootworm eggs to pass through two or more winters before hatching rather than the normal one-year pattern; this permits larvae to damage corn following another crop. Researchers found that the percentage of eggs showing this trait was nearly twice as high for eggs maintained at 4šC than for eggs maintained at either 8 or 10šC for five months. This suggests that environmental conditions may play a big role in the expression of the prolonged diapause trait. Previously our researchers reported that there is a genetic component to prolonged diapause as well.

Microsporidian host specificity
L. Solter, J. Maddox
Host specificity is the most important question relative to the safety of biological control agents. Most studies on host specificity have been conducted in the laboratory and have generally produced yes (susceptible) or no (not susceptible) results. INHS research on microsporidian pathogens of insects has shown that, in the laboratory, host specificity is influenced by a complex set of variables that seldom produces a simple yes or no result. Additionally, Survey studies are indicating that, in the field, most species of microsporidia are host specific.

Mosquito eggs survive waste-tire chopping
S. Hanson, R. Lampman, R. Novak, P. Purseglove (Illinois Environmental Protection Agency)
Tires that were either crudely chopped or more finely processed into shreds had viable eggs. Field-collected remnants of two to three chopped tires had a viable Aedes albopictus egg. After shredding tires that were seeded with mosquito eggs, 34 (4.6%) of an estimated 746 Ae. albopictus eggs and 21 (2.7%) of an estimated 774 Aedes triseriatus eggs survived. Chopped and shredded tire remnants may serve as a means of dispersing mosquitoes.

Spatial dynamics of potato leafhopper
S. Roberts, E. Armbrust
The potato leafhopper is a serious pest of alfalfa causing losses in forage crop production that results in reduced quality and quantity. Adult leafhoppers migrate into Illinois during the spring and often inhabit hosts other than alfalfa prior to reaching pest status on alfalfa. Monitoring interhabitat movement of potato leafhopper adults provides information to predict when and why leafhoppers develop as pests in alfalfa. Using sticky traps, movement was monitored at six diverse sites in St. Clair County at the Southern Illinois University Belleville Research Center.

Dispersal of Aedes albopictus in Illinois
R. Lampman, S. Hanson, R. Novak
Although several major tire sites are undergoing cleanup, little is known about whether this will limit the spread of Ae. albopictus. The Asian tiger mosquito is both a potential vector of several arboviruses and a major nuisance pest. Researchers recovered this species from sod-baited gravid traps at seven test sites in southern Illinois. Five of these test areas (Newton, East St. Louis, Mounds, Ullin, and Campbell Hill) were within 0.5-1.0 km of a waste-tire site, whereas the other positive areas (Red Bud and Steeleville) did not have an obvious source of tires.

Mosquito variation at a waste-tire yard
R. Lampman, S. Hansen, R. Novak
Urban and rural tire dumps are foci for the proliferation and dispersal of numerous vector and nuisance mosquitoes. Ten mosquito species were collected from tires at a tire yard in Jasper County. Based on collections from three different times of the year, the most abundant early species is Aedes atropalpus. Culex pipiens and Ae. albopictus are the most abundant species late in the season. Various species also exhibited preferences for tires that were either shaded and near trees or those that were in an open meadow. Follow-up studies will determine how the cleanup of this site affected species abundance.

Assay for western corn rootworm oviposits
M. Vodkin, E. Levine, R. Novak
Within the last three years, increasing numbers of farmers in Illinois who annually rotate corn have been experiencing problems with damage from the western corn rootworm (WCR). Circumstantial evidence suggests that the WCR has overcome rotational strategy by ovipositing in soybeans. In order to monitor the scope of the problem prior to crop damage and identify fields or areas at risk, a surrogate assay is under development. Insect-specific primers were designed to amplify the internal transcribed spacer region, and the 1,100 base-pair product from individuals that oviposited in either corn or soybean is being sequenced to compare differences.

Algorithm for discontinuous, linked queries
M. Vodkin, R. Novak
Public and commercial programs are available to search for sequences in the nucleic acid or protein databases that are homologous to a query. However, the popular programs are ill-suited to manipulate discontinuous data that are frequently encountered with RAPD analysis (oligonucleotides) or N-terminal analysis of a partial proteolytic digestion (oligopeptides). A strategy was designed using an extant program, FindPatterns, in the University of Wisconsin GCG package, to manipulate such data. The program was successful in identifying a previously unidentified protein from a data set.

Surveys

Monitoring vectors of St. Louis encephalitis
R. Lampman, R. Novak
Culex mosquitoes, vectors of St. Louis encephalitis, lay their eggs in areas that contain water with a high organic content. Various materials have been used to mimic these natural oviposition sites in order to attract mosquitoes to traps. Baited traps allow monitoring of oviposition or collection of female mosquitoes for surveillance of arboviruses. Our research showed that the number of egg rafts oviposited in infusion-baited traps varied with the type of infusion substrate, infusion age, method of infusion preparation, and calendar date. The most attractive infusions included grass sod, yard-grass clippings, and a commercial rabbit chow.

Attractants for the Asian tiger mosquito
R. Lampman, R. Novak
Aedes albopictus adults were recovered from sod-baited gravid traps at seven sites in suburban and rural areas in five counties of southern and southwestern Illinois. Olfactometer and oviposition preference tests in the laboratory showed that Ae. albopictus is attracted to sod infusion and readily oviposits on substrates in contact with the infusion. At a waste-tire site in Jasper County, Illinois, Ae. albopictus, Ae. triseriatus, and Culex species were collected from sod-baited gravid traps. The presence of the Asian tiger mosquito in wooded areas suggests it may compete with the native tree-hole mosquitoes for larval habitats.

RT-PCR for detecting St. Louis encephalitis
M. Vodkin, J. Siegel, R. Novak
This laboratory has published a prototype assay for the St. Louis encephalitis virus (SLEV) and used it successfully in studies with small numbers of mosquito pools. A large, blind study was designed to compare the efficacy of detecting SLEV by the RT-PCR with that of two other accepted procedures, enzyme-linked immunoassay and tissue culture. A set of 1,725 mosquito pools was assembled and tested concurrently by the three methods. The RT-PCR was 88-99% sensitive, specific, and accurate as compared to the two "gold standards." It was also competitive in economic costs.

Mosquito surveillance for SLEV virus
M. Vodkin, R. Novak
Much of the work on the abundance of mosquito vector species and frequency of SLEV in the vector derives from epidemic years. However, objective guidelines have not been established to determine when mosquito abatement should be implemented. During 1993 in Chicago, an interepidemic season, the serum from 408 captured passerine birds was analyzed for SLEV-specific antibody, and 134 pools of adult mosquitoes were analyzed for SLEV by the reverse transcriptase-polymerase chain reaction. The prevalence for SLEV was 0.2% in birds and 0.02% in mosquitoes, about 25-fold less than normally occurs in an epidemic.

Pine shoot beetle survey
C. Helm
In cooperation with Illinois Department of Agriculture and federal Plant Protection and Quarantine officials, Survey scientists are participating in a 21-county trapping program adjacent to known areas of infestation of the common pine shoot beetle. Since its initial detection in Illinois in 1992, a total of 18 counties encompassing the northeast quarter of the state have been quarantined to help prevent the spread of this newly introduced pest. Surveys of IDNR-managed lands with established stands of pines will help determine the impact of this pest outside of commercial Christmas tree plantations.

A survey of mosquito larvae in urban areas
S. Hanson, R. Novak, R. Lampman, M. Vodkin, W. Ruesink
All land-use zones (cemetery, commercial, industrial, institutional [schools and public properties], recreational [parks and golf courses], residential, and roadway) in Champaign and Urbana were surveyed for mosquito larvae June 21-22 and August 14-15, 1996. Mosquito larvae were not present in commercial and institutional areas. Larvae were most abundant in the residential zone, more so in residential neighborhoods with lower per capita incomes. The most numerous species was Culex restuans, a potential vector of St. Louis encephalitis virus.