1)Project title: The biology of Rosa multiflora and two of its biotic mortality factors

Investigators: Laura C. Jesse, John J. Obrycki, and Kirk Moloney, Iowa State University, Departments of Entomology; and Ecology, Evolutionary, and Organismal Biology

Contact: Laura Jesse (lrahnsen@iastate.edu)

Project description: Rosa multiflora Thunb. (Rosaceae), an invasive plant, reduces the value of land for grazing or recreational purposes because dense patches of the plant are impassable and are not fed upon by most livestock. Two biotic mortality factors may offer long-term suppression of R. multiflora, but require further investigation to determine spatial and temporal patterns in levels of mortality. Rose Rosette Disease (RRD) has been investigated extensively and is believed to suppress R. multiflora densities. However, the long-term cycling and effects of RRD in R. multiflora populations and the role of the presumed mite vector in the spread of RRD has not been described or quantified. Megastigmus aculeatus Hoffm. (Hymenoptera: Torymidae), is a wasp whose larvae feed on R. multiflora seeds. The effects of M. aculeatus on viable R. multiflora seed production and the seed bank need to be investigated further. Currently there is no information on the distribution and relative abundance of this wasp in Iowa.

The objectives of my research are to 1) Determine the mechanisms by which R. multiflora infestations spread within selected habitats, i.e., by vegetative growth or the spread of seeds, 2) Determine if habitat (shade vs. sun locations) influences the distribution of P. fructiphilus, the mite vector of RRD, 3) Determine the distribution and over-wintering survival of M. aculeatus in selected locations in Iowa, 4) Quantify number of hips attacked and seeds fed upon by M. aculeatus, 5) Determine the role birds play in spreading M. aculeatus within R. multiflora seeds within and among R. multiflora infestations

2) Project Title: Multitrophic interactions in wetlands infested by purple loosestrife, Lythrum salicaria L

Investigators: Bethzayda Matos-Carrion, Gail Nonnecki, and John J. Obrycki, Iowa State University, Departments of Entomology and Horticulture

Contact: Bethzayda Matos-Carrion (bmatos@iastate.edu)

Project Description: Two chrysomelid species, Galerucella calmariensis L. and Galerucella pusilla Duftschmid (Coleoptera: Chrysomelidae) were introduced to reduce L. salicaria. In 1992, another insect, Myzus lythri (Schrank) (Homoptera: Aphididae) was observed feeding in abundant numbers on L. salicaria in Indiana. However, reduction in plant biomass has not been observed and data has been collected that supports a hypothesis that native natural enemies may be limiting L. salicaria predator densities. In a laboratory study conducted this past semester (Spring 2003), I quantified the survival and mortality rates of three predators: C. maculata, C. carnea, and H. axyridis on M. lythri. Eighty percent of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) survived on M. lythri whereas only 20% of C. maculata and C. carnea survived. Future research objectives include: 1) comparing responses by predators and plants when Galerucella spp. and Myzus lythri are in the same system, 2a) examining interactions between M. lythri and Galerucella, 2b) examining the effects of intraguild predation among C. carnea, C. maculata, and H. axyridis when the prey is Galerucella and M. lythri, 3) preparing a life table analysis, 4a) comparing the complex of predatory insects on herbivores feeding on L. salicaria in Germany with Iowa, and 4b) measuring plant responses when herbivores are artificially removed from L. salicaria loosestrife in Germany and Iowa by using enclosures and safer soap sprays.

3) Project title: Post-dispersal weed seed predation in contrasting herbaceous crop systems

Investigators: Fabian D. Menalled, Andy H. Heggenstaller, and Matt Liebman
Iowa State University, Department of Agronomy

Contact: Fabian Menalled (menalled@iastate.edu)

Project description: Weed seeds consumption represents a significant source of mortality and a valuable component of integrated weed management programs that seek to increase reliance on ecological processes and reduce dependence on mechanical and chemical control practices. In this project we assessed post-dispersal seed predation of two weed species [Setaria faberi (giant foxtail) and Abutilon theophrasti (velvetleaf)] in two-, three-, and four-year rotation systems. The two-year rotation sequence (corn-soybean) dominates agriculture in the Midwest U.S. The three-year sequence (corn-soybean-triticale + red clover) includes a legume green manure as a source of N. The four-year rotation sequence (corn-soybean-triticale + alfalfa-alfalfa) is suitable for farming systems with ruminants. Seed predation experiments were conducted between May and October 2003 using two treatments: (1) total exclosures that prevented vertebrates and invertebrates from removing seeds and that were used to assess the experimental error inherent in seed recovery, and (2) no exclosures that allowed both vertebrates and invertebrates to consume weed seeds. Temporal patterns of giant foxtail and velvetleaf seed removal were similar. However, these patterns were crop-specific and closely associated with canopy closure. While weed seed removal in corn and soybean plots increased during the growing season as the crop canopy closed, weed seed removal in alfalfa showed periodic peaks associated with dense canopies prior to mowing, and weed seed removal in triticale showed a maximum in July 2003 prior to harvest. Sensitivity analysis of population dynamics models indicates that weed seed predation, as a component of seed mortality, represents an important variable determining weed abundance in agricultural fields.

4) Project title: Carabid beetle (Coleoptera: Carabidae) activity-density and invertebrate seed predation in a two- and four-year crop rotation system in Iowa

Investigators: Megan O’Rourke, Fabian Menalled, Matt Liebman, and Marlin Rice, Iowa State University, Departments of Agronomy and Entomology

Contact: Megan O’Rourke (megorust@iastate.edu)

Project description: Ground beetles (Carabidae) can be important in the biological control of insect pests and weeds. During 2003, we compared carabid activity-density and community composition in two- and four-year crop rotation systems in Iowa. The two-year system uses a corn/soybean sequence, whereas the four-year system uses a corn/soybean/triticale (underseeded with alfalfa)/alfalfa sequence. Invertebrate weed seed predation on Setaria faberi (giant foxtail) and Abutilon theophrasti (velvetleaf) was also evaluated in July using invertebrate exclosure cages. Results suggest that crop phase is more important than rotation system in determining carabid activity-density and community structure. The dominant carabid beetle caught was Poecilus chalcites which comprised over 70% of the carabid samples, with granivorous species comprising only about 3% of the carabids. There were more carabids caught in the two and four year soybeans (s2 & s4), triticale (t4) and alfalfa (a4) plots than in the two- and four-year corn (c2 & c4). Carabid community diversity was significantly higher in the triticale than in all other cropping treatments. Seed predation trials indicated that there was no significant weed seed removal by invertebrates in either the two- or four- year crop rotation systems in July.

5) Project title: Insect predation of common waterhemp (Amaranthus rudis) and common lambsquarters (Chenopodium album) seeds in three different tillage regimes.

Investigators: Rocio van der Laat, and Micheal Owen, Iowa State University, Department of Agronomy

Contact: Rocio van der Laat (rociov@iastate.edu)

Project description: Preliminary studies were conducted in Boone County, Iowa in July and August 2003 to evaluate invertebrate seed predation of common waterhemp (Amaranthus rudis) and common lambsquarters (Chenopodium album) in conventional, reduced, and no-tillage corn. We found higher weed seed predation in conventional and reduced tillage compared to no-tillage, for both weed seed species.

In future research, we will: 1) identify and quantify the populations of important insect granivores, 2) determine a correlation of potential insect predator frequency with the level of weed seed predation, 3) determine if differences in weed seed predation rates reduce the number of weeds per area, and so increase crop yield, 4) describe feeding ability and weed seed preference of the potential predator invertebrates.

6) Project title: Biological control of the soybean aphid in organic and sustainable
soybean production systems

Investigators: Junwei Zhu, and Rick Exner, Iowa State University, Department of Entomology and Practical Farmers of Iowa Extension

Contact: Junwei Zhu (jwzhu@iastate.edu)

Project description: The soybean aphid, Aphis glycines, was first detected in Wisconsin in 2000 and continues to spread throughout the U.S. with more than 20 states reporting infestations. The damage caused by this aphid can lead to more than 50% yield reduction in soybeans. This project is exploring the manipulation of beneficial insects via plant derived, olfactory attractants to suppress soybean aphid populations. This new technology may provide a means for organic soybean growers to control aphids. Intensive efforts have been made to work cooperatively with farmers to conduct on-farm research trials.

7) Project title: Effects of prey density on adult characteristics of three species of Coccinellidae

Investigators: Susan E. Moser, and John J. Obrycki

Contact: Susan E. Moser (moser@uiuc.edu)

Project description: Larval nutrition is an important factor determining adult characteristics, which influence the population dynamics of a species. Responses to larval development on 4 levels of pea aphids per day [2, 4, 10, and 20 Acrythosiphon pisum Harris (Homoptera: Aphididae)] were determined for Harmonia axyridis Pallas (Coleoptera: Coccinellidae), Coccinella septempunctata L. (Coleoptera: Coccinellidae), and Coleomegilla maculata De Geer (Coleoptera: Coccinellidae). Characteristics measured included development time, survival, sex ratio, adult weight, length and width of adult elytra, and shape of the elytra. Survival was not influenced by an individuals’ sex. The response of body size (adult weight, elytral length, elytral width) was affected by prey levels for each species. Only H. axyridis completed development at each prey level and consistently increased body size as prey levels increased. At 2 and 4 aphids per day, Coleomegilla maculata had the highest survival (%) and fastest development time (days). Coccinella septempunctata larvae did not complete development when fed 2 aphids per day. Maternal effects were observed to influence larval and adult characteristics of each species

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