Agricultural management and farm nutrient budgets

Zaborski, E. and L. Soeken

Agroecosystems are unique in that they are heavily subsidized with nutrient and energy inputs. The choice of management practices can significantly alter the balance and flow of nutrients in and through the system, and affect the efficiency with which these nutrients are used and recycled. Using records and estimates of inputs and exports such as seed, fertilizers, nitrogen fixation, atmospheric deposition, yields and soil erosion, we are comparing nutrient budgets for corn-soybean rotations with or without tillage and 4-yr organic cash grain rotations on the Stewardship Farm in Piatt County, Illinois.

Amynthas hupiensis, a megascolicid earthworm new to Illinois

Zaborski, E. and L. Soeken

Amynthas hupiensis was recently collected in Champaign County, Illinois. This increases the number of earthworm species reported from Illinois to 37, and the number of megascolicid earthworms from Illinois to three. Like eighteen other species of Illinois earthworms, including all the megascolicid earthworms, A. hupiensis is not native to North America. Originating in southeast Asia, it was first collected in North America in 1910 in Washington, D.C. Since then it has spread to other states, possibly as fish bait or through the horticultural plant trade in soil on plant roots or sod.

Bees and pollination

Bouseman, J.

The bee fauna of Illinois has been studied for over 30 years with emphasis on the pollen host relationships and in particular the host-relationships of oligolectic bees. I have been especially interested in the pollination of prairie and aquatic plants, e.g. Asclepias, Helianthus, Opuntia, Hibiscus, and Pontederia and in the pollinators of cultivated curcurbits.

Bipalium adventitium, an earthworm predator newly reported in Illinois

Zaborski, E.

Recently, specimens of Bipalium adventitium were collected in Champaign County, Illinois. B. adventitium is a land planarian probably introduced accidentally from SE Asia to North America during the 1900s on plant roots. To date, it has been reported from CA, CT, MA, MD, NY, PA, TN, and WA. B. adventitium feeds on earthworms. In laboratory trials, specimens collected from Urbana attacked all species of earthworms presented to it, including species not previously reported as prey. They attacked earthworms up to 10 times greater in weight, and doubled in weight after feeding. Earthworms rarely survived attacks.

Characterization of western corn rootworm egg-laying behavior

Spencer, J.

Egg-laying of western corn rootworms (WCR) was observed. WCR egg-laying occurs as a series of bouts where one to several eggs are deposited followed by a pause of several minutes before resumption of examining and egg-laying. The egg-laying rate seems to slow as a females eggload declines. Egg-laying in WCR is under constant inhibition as decapitation stimulates immediate egg-laying. Patterns of egg-laying bouts and pauses by headless females are similar to those of intact females, however, the egg-laying rate does not decline. Headless females lay eggs at a rate three times faster than intact females. Efferent signals that would normally modulate the egg-laying rate are absent in headless WCR.

Consumption of soybean foliage reduces vigor of adult western corn rootworms

Spencer, J. and T. Mabry (UIUC), S. Isard (UIUC), Levine, E.

WCR that fly to soybean fields consume soybean foliage. Soybean herbivory reduces the vigor of WCR compared to corn-fed individuals. In mortality tests, female WCR from soybean fields died significantly sooner than individuals from cornfields. The negative effects of soybean herbivory can be mitigated by feeding on corn tissues. Access to corn plant tissues made soybean field-collected WCR as tolerant of starvation as WCR collected in cornfields. Wind tunnel flight-tests reveal that soybean-fed WCR had significantly increased tendencies to fly. We hypothesize that increased flight after eating soybean foliage is the proximate mechanism that facilitates beetle movement back to cornfields for feeding.

Daily patterns of western corn rootworm flight between corn and soybean fields

Spencer, J. and S. Isard (UIUC), Levine, E.

Malaise traps were used to monitor western corn rootworm (WCR) flight between corn and soybean fields from 1997-1999. Flight activity was low in the early morning when air temperatures were cool. Aerial movement peaked between 700 and 1100 (solar time). During the first half of this period immigration to soybeans exceeded emigration, thereafter the reverse was true. Before sunset (1700-1900) activity again increased. WCR are not caught in malaise traps during darkness. Micrometeorological measurements indicate the peak WCR flight is associated with periods when wind speed and temperature gradients above the soybean canopy create unstable atmospheric conditions that facilitate WCR flight.

Earthworm communities in Illinois agroecosystems

Zaborski, E. and L. Soeken

Earthworms are important biological components of the soil resource in Illinois. In central Illinois fields with corn-soybean rotations, with or without tillage, and corn fields following a perennial forage with tillage, we identified eight species of earthworms, all introduced. Colonization of Illinois soils by these species is recent and may still be in progress. Fields may lack some species simply because they have not yet been colonized, making it difficult to see the influence of management and environmental factors on the structure of the earthworm community.

Ecological host range of microsporidia

Solter, L. and D. Pilarska (Bulgarian Academy of Sciences), C. Vossbrinck (Connecticut Agricultural Experiment Station)

The ability of laboratory studies to predict the host specificity of microsporidia in the field was evaluated in field studies of the pathogens in the area in which the gypsy moth host originated. One of eleven microsporidian isolates recovered from nontarget Lepidoptera infected the gypsy moth. Ribosomal DNA sequencing confirmed that this noctuid pathogen was not the same as those found in the gypsy moth. Nontarget hosts were not infected with gypsy moth parasites. The results of the field tests therefore supported the laboratory predictions.

Ecology of a trichopteran microsporidia

Heilveil, J.(UIUC) and L. Solter

A microsporidium that causes complete diebacks of its caddisfly host in cold water streams is not orally infective to other caddisfly larvae. It may have an unknown obligate intermediate host. Microsporidian isolates have been recovered from two copepod species found in the same streams and are undergoing molecular analysis to determine if one of them is the same species as that which occurs in the caddisfly.

Host relationships of Kyrghyz bees and Meloid beetles

Bouseman, J.

In August-September of l998 and June-July of l999, I participated in international expeditions to the Tien Shan of Kyrgyzstan. Collections were made in all six administrative districts (Chuy, Talas, Jalal-Abad, Osh, Naryn, and Yssk-Kol) of the Kyrgyz Republic. The goal of this work is to better understand the fauna of the region and to elucidate host-relationships of a part of that fauna. Kyrgyzstan lies in the heart of Central Asia at the same latitude as Illinois. Hence it is a likely potential source of imported pest species for Illinois, e.g. this area is the home of the cultivated apple in all of its varieties and also the home of the codling moth.

Laboratory host range of microsporidia

Solter, L. and J. Maddox

Most experiments designed to test the host specificity of insect pathogens are conducted in a laboratory setting and, therefore, test the physiological host range of the pathogens but not the host range in the field, the ecological or realized host range. Laboratory studies, which are necessary before release of exotic pathogens into the environment for purposes of biological control, were designed to reflect the host specificity in the field as closely as possible. The results of the experiments suggest that microsporidia (a group of entomopathogens in the protozoan group) are quite host specific and that field range will be much narrower than the laboratory host range.

Movement and mating of adult western corn rootworms in east central Illinois cornfields

Spencer, J. and E. Levine, S. Isard (UIUC), D. Onstad (UIUC)

Fluorescent powder was used to mark 4,700 western corn rootworm (WCR) beetles before release within concentric rings of insect traps. WCR move quickly through cornfields. After release, WCR were re-captured up to 250 meters away. Average rate of WCR movement was 0.67 m/hr for males and 0.91 m/hr for females. Mating of virgin female WCR was observed in cornfields. Unmated female WCR were surprisingly active. Many virgin females flew away before mating could be observed. The mean interval between female release and finding males was 24.7 min. Males locate calling females in corn via slow, hovering flights. Swirling air currents in corn may prevent males from orienting to single pheromone plumes.

Pathogen-pathogen interactions

Solter, L. and D. Pilarska (Bulgarian Academy of Sciences), K. Higgs

The interactions of different pathogen species in a single host or host population can influence the effects of each pathogen on the host population. A single insect species can host several species of microsporidia (a group of entomopathogens in the protozoan group) but usually only one species of microsporidia is present in a local host population. Laboratory studies are underway to determine how different combinations of microsporidian species isolated from the gypsy moth, Lymantria dispar, interact in a single host individual.

Physiological effects of microsporidia

Henn, M. (Technical University of Munich, Germany), L. Solter

The effects of microsporidia infection on the gypsy moth host were studied as they relate to the invasion and reproduction of the pathogen in the host fat body, the most important metabolic tissue of insects. Reduction in growth parameters coincided with a period of extremely intensive development and reproduction of a Vairimorpha species in the gypsy moth host.

Physiological host-parasite interactions

Wiedenmann, R. and M. Alleyne (UIUC)

Successful use of parasitic insects for biological control requires them to be physiologically compatible with their hosts. The level of compatibility also determines physiological host range of parasites, thus their specificity. Three Cotesia species show different levels of compatibility with related stemborer hosts. The main host defense -- the immune response -- is overcome to different degrees by each parasite species. The differences in host compatibility suggest these parasites will have a narrow host range, and have little impact on non-target species, but explicit testing will be needed to assure safe use of these parasites.

Prescribed burning and soil and litter invertebrates in oak-hickory forests

Zaborski, E. and L. Soeken

Since the suppression of fire as a factor in Illinois' prairie peninsula during the 20th century, relatively dry upland oak-hickory savannas and forests have been invaded by fire and sensitive, shade tolerant plant species such as sugar maple, slippery elm and paw-paw. Natural area managers are now reconsidering the use of fire to maintain the integrity of these unique biological communities. In several eastern Illinois locations, we are monitoring soil and litter invertebrate populations in control and burned plots to better understand the influence of fire in these communities.

Rapid assay to predict oviposition behavior

Lampman, R. and R. Novak

This investigation tested the genetic differences between a populations of the western corn rootworms (WCR) found in soybean or corn fields. DNA analysis from the two populations provided 2 bands that correlated to where a individual was collected. Sequence analysis revealed that these bands were composed of different DNA products, including a terminal retrotransposon, The affected genes were identified as an olfactory binding protein and an esterase. Both segments matched a nematode worm unrelated to the WCR. The data, suggests that the WCR's sampled were contaminated, thus making it necessary to screen WCR individuals for the presence of nematodes before searching for molecular differences.

Response of rootworms to plant volatiles

Hibbard, B. (USDA) and E. Levine, D. Duran (USDA), N. Gruenhagen (USDA), J. Spencer

Electrophysiological (EAG) studies were conducted to determine whether differences exist between normal and rotation-resistant western corn rootworms in regard to their response to corn and soybean volatiles. The rotation-resistant population was not significantly more responsive to soybean volatiles, nor was it less capable of detecting corn volatiles than the normal population. These data suggest that specific attraction to volatiles from soybeans is unlikely to be the mechanism responsible for movement into soybean fields and subsequent egg-laying by the rotation-resistant population.

Rootworm transmission of soybean virus

Levine, E. and J. Spencer, S. Isard (UIUC), H. Hobbs (UIUC), G. Hartman (UIUC), W. Pedersen (UIUC).

Bean pod mottle virus (BPMV) is a disease of soybeans in which the stems of infected plants remain green after the plant is mature. In addition to causing harvest problems, plants with BPMV are predisposed to other diseases which lower seed quality. In 1999 we discovered that some of the western corn rootworm beetles we collected in soybeans contained this virus. We are currently conducting BPMV transmission studies to determine if western corn rootworms are capable of spreading this disease.

Rootworms in alfalfa and soybean fields

Lampman, R. and R. Novak. H. Hummel (University of Griesen, Germany)

The most damaging pests of corn are the western corn rootworm (WCR), and the northern corn rootworm (NCR). The farming practice of rotating corn and soybeans has selected for changes in the dispersal, feeding, and oviposition behaviors of WCR. This study investigated the impact of these altered behaviors to semiochemicals in an area with first-year corn rootworm problems. Non-pheromonal lures, 4-methoxycinnamaldehyde (MCA) and 4-methoxyphenethanol (MPE), attracted WCR and NCR, in soybeans. These lures continue to be tools for manipulating behavior in non-corn crops. High abundance of NCR on baited traps in soybeans was unexpected. Sweep net sampling indicated that both species were present in soybean and alfalfa fields.

Seasonal patterns of western corn rootworm abundance in adjacent corn, soybeans and other crops

Spencer, J. and E. Levine, S. Isard (UIUC), T. Mabry (UIUC)

Vial traps were used to monitor WCR abundance in corn, soybeans, oats, and alfalfa. Patterns of WCR abundance in east central Illinois corn and soybean fields vary from year-to-year. WCR are first detected in soybean field vial traps within 7 to 10 days of the first WCR detection in adjacent cornfields. Populations in soybean fields usually exceed those in cornfields within one week of WCR detection in soybeans. Mean WCR/vial trap/day was significantly greater in soybeans than in corn. Along a transect through soybeans, oats, alfalfa and corn, WCR abundance in corn was significantly less than that in soybeans but not different from that in alfalfa. WCR numbers in oats were less than those in all other crops.

SoilWatch: Monitoring the health of Illinois soils

Zaborski, E. and L. Johns

Soil is among Illinois' most valuable resources; SoilWatch is being developed to provide procedures for assessing and monitoring soil condition in Illinois. This year, we focused on identifying methods to determine the effort required to reliably detect meaningful trends in physical, chemical and biological indicators of soil condition. We also compiled published information and collected new field data to begin these assessments for physical and chemical indicators, and we conducted field trials to improve biological monitoring procedures and begin assessing their power to detect trends.