Overall plan of action
We will complete the evaluation of the host-specificity of the natural enemies we currently have in culture and expand testing to include other species as they become available. We will use field research in the US and in Asia to evaluate the relative risks of natural enemies of soybean aphid to non-target species. These two sets of studies will be used to identify suitable candidates for field release and evaluation of control efficacy. Once we have identified a natural enemy that holds promise to provide economic control of the aphid, we will make it available to cooperators throughout the Midwest for area-wide release and subsequent control evaluations.

Throughout the grant period, we will work with local Extension offices and soybean producer groups to inform growers of the effectiveness of biological control of soybean aphid. A Coordinating Committee, comprised of one representative per state, will oversee project progress, evaluate research results and extension efforts, and communicate findings to NCSRP and local soybean boards.

Executive Summary
The project initiated work on all objectives in a year that saw an extensive outbreak of soybean aphid throughout the Midwest. Work on the host specificity of soybean natural enemies continues to show promise, with good (relatively high) specificity found for 3 “exotic” (Asian) natural enemies. For one of these, an “Environmental Assessment” was prepared and submitted to the USDA/APHIS for regulatory review.

A rearing-release method was tested in Minnesota and showed good results to rapidly increase natural enemy densities using field-cage techniques. Travel to Asia initiated collaborative research in both Japan and China, and further exploration for natural enemies in those countries, as well as South Korea.

Research on potential non-target impacts on native aphids was initiated in several states. A list of native aphid species potentially at risk from Asian soybean aphid natural enemies was developed and sampling of these aphids in several habitats in 4 North Central states will initiate in the spring 2006. Complementary studies have begun in Japan and China.
A suction trap network was initiated to provide information on aphid species diversity and relative abundance. The network operates 32 traps in 7 North Central states.

Toxicity of several pesticides to soybean aphid natural enemies was tested, and these data are being used to recommend chemicals that are less toxic to the aphid’s natural enemies. Studies of intra-guild predation (attack of one natural enemy against another) among soybean aphid natural enemies were initiated in the US and in Asia.

Work progressed on Extension/Education efforts. All states reported talks, field days and growers meeting where the topic of soybean aphid biological control was discussed. A photographic library of soybean aphid natural enemies and this website (Soybean Aphid Biological Control) was prepared and drafts of information on the field of biological control, natural enemies, and our soybean aphid project were developed.

We continue to leverage support and link our efforts to related work in soybean aphid ecology and management. For example, a number of chemical companies have augmented NCSRP funding for research into pesticide impacts on natural enemies being conducted at Iowa State. Our collaborators in Japan have applied for government funding to support their contribution to our research on non-target impacts. Several states report funding from USDA and local soybean board sources.

Several graduate students have been recruited to conduct project related research (primarily related to objective 1). Included are students at Iowa State, Purdue, Illinois, and Minnesota. In addition, 3 post-doctoral associates have been recruited to work on project research in Minnesota (2), and Wisconsin (1). We expanded the project with the inclusion of a new state, South Dakota, via the collaboration of Dr. Kelley Tilmon of South Dakota State University. In addition, Dr. Kim Holemer of the USDA/ARS Newark, Delaware laboratory expanded the our efforts on foreign exploration for soybean aphid natural enemies in Asia.

We publicized our NCSRP project in a number of Extension Newsletters, trade magazines and scientific journals. Our project was widely reported at a symposium (Ecology and Management of The Soybean Aphid) held at the 2006 meetings of the North Central Branch of the Entomological Society of America. Finally, the project’s Coordinating Committee met in St. Louis in April 2006.

Objective 1: Determine the potential for establishment, safety, and compatibility of
imported natural enemies of the soybean aphid.
Heimpel (MN), Gratton (WI), O’Neil (IN), Landis (MI), O’Neal (IA),
Voegtlin (IL), Hopper, Hoelmer (USDA)

1. Host specificity testing
Research continued on host specificity testing at the University of Minnesota (focusing on the braconid parasitoids, 6 species/populations) and the USDA/ARS lab in Newark, Delaware (focusing on the aphelinid parasitoids, 15 species/populations). At UMN, host specificity testing of Binodoxys communis strains from both China and Japan indicate an intermediate level of host specificity.

Of all the species tested, it does best on soybean aphid, attacks eight other aphid species at lower levels, and produces no offspring at all on six other species. While soybean aphid is the most suitable host, the parasitoid will attack native aphid species, including Aphis monardae, a native non-pest aphid that inhabits prairies and is therefore a non-target species that may be at risk if B. communis is released. To evaluate this risk further, surveys of A. monardae in native prairie settings were made throughout southern Minnesota. We found it abundant in both undisturbed prairie remnants and parkland meadows. During these observations, we also noticed that (i) this aphid tends to cluster in flower heads of its host plant, Monarda fistulosa, and that (ii) many of these aphid colonies are tended by ants (Lasius sp.). Both of these factors may decrease the risk of introduced B. communis to the native A. monardae. We are currently conducting studies to test the ability of B. communis to attack A. monardae that are clustered in M. fistulosa flowerheads, and being tended by ants.

At the USDA/ARS research continued to focus on parasitism by populations of the Aphelinus-varipes complex collected from China, Japan, and Korea. The aphid species tested included Aphis glycines, Aphis gossypii, Diuraphis noxia, Myzus persicae, Rhopalosiphum maidis, Rhopalosiphum padi, and Schizaphis graminum. We reared and exposed Aphis glycines on soybean; Aphis gossypii on cotton; Myzus persicae on radish; and Diuraphis noxia, Ropalosiphum maidis, Rhopalosiphum padi, and Schizaphis graminum on barley. Parasitism varied with aphid species and with parasitoid populations, with some parasitoid populations having narrower host ranges than others. Material from Heilongjiang Province in China and from Korea attacked A. glycines and R. padi more than the other aphid species, and by this measure had the narrowest host range. Plans are to test the ecological host range of this population.

2. Intraguild predation
A graduate student at the University of Minnesota initiated experiments to evaluate which of the parasitoids that are in culture are most compatible with resident natural enemies, in particular the multicolored Asian lady beetle, Harmonia axyridis. This research will be complimented by planned work in China in summer 2006 to observe and quantify some of these interactions in the field as a means of determining which parasitoid species are able to attack soybean aphid in the presence of predatory insects. To help determine the compatibility of released and U.S. natural enemies of soybean aphid, the extent to which Binodoxys and Aphelinus mummies were preyed upon in the field in the native home, China, was assessed.

By collecting mummies and examining whether or not they had been consumed by predators, it was shown that predation on B. communis was approximately half that on Aphelinus sp. Since the mummy state of Aphelinus is approximately twice as long of that of B. communis, this is consistent with a similar rate of predation on both species. From the standpoint of compatibility with predators though, these data suggest that B. communis escapes predation better by virtue of its shorter development time.

3. Non-target research
In Asia, work proceeded on a number of fronts. In China, an initial evaluation of field host range of soybean aphid natural enemies was done. Parasitoids from three aphid species on three host plant species: cotton aphid (Aphis gossypii) on cotton, corn leaf aphid (Rhopalosiphum padi) on corn, and soybean aphid (A. glycines) on soybean. The identity of the parasitoids will be confirmed through comparison of their host use, molecular markers, and reproductive compatibility.

From the material collected in China, cultures of Binodoxys sp. from soybean aphid, an Aphidius sp. from corn leaf aphid, and Aphelinus sp. from both species of aphids were established. In other work, collections of aphids and natural enemies were made in Japan and China on soybeans, wild soybeans (Glycine soja) and Rhamnus spp. Included in collections were the natural enemies of soybean aphids and other aphid species living in close association with them. Natural enemies are being reared for identification purposes. Cooperative agreements were made with the University of Utsunomiya, Japan, and the Chinese Academy of Sciences. These agreements will allow year-round collections of aphids and associated natural enemies, in and around the soybean aphid host plants (Rhamnus and Glycine spp.). Comparison of the natural enemies of soybean aphids to these “non-target” aphids will give insight into the field host ranges of Asian natural enemies, and inform on our US studies of potential non-target impacts on native US aphid species.

In US work, the suction trap network became operational in summer 2005 with 32 traps in Illinois, Indiana, Michigan, Wisconsin, Minnesota, Kansas, and Iowa. A web site was developed to report data for catches of the soybean aphid (www.ncipmc.org/traps). Weekly counts for 15 other aphid species are also sent to cooperators in the respective states. In addition to these, other aphid species are reported as they are identified. Findings from suction traps show that although many common species are present throughout the Midwest their abundance is highly varied. The trap catch data will assess the relative abundance of native aphid species that may be utilized as hosts by any of the released exotic natural enemies. The University of Illinois graduate student on the project, Ms. Doris Lagos, is working on key to the Aphis species of the Midwest, which will be critical in identify potential non-target species.

We compiled a list of aphids (Aphidinae and Macrosiphinae) found in Illinois along with their hosts and life cycle. Using this list we developed a matrix to place native aphid species on a continuum of “attack risk” based on their relative abundance, and host plant range. (We assume that a common aphid on a common host would have a higher chance of being utilized by a released exotic natural enemy than a rare aphid on a rare plant.). The matrix will be used to direct survey efforts to assess potential non-target impacts and inform host-specificity research.

4. Insecticide compatibility
The Soybean Entomology Laboratory at Iowa State tested several insecticides that may have a limited impact on imported natural enemies. Of the products tested, two (Fulfill and Trimax) performed very well against soybean aphids, lowering populations to the same level as that of broad-spectrum insecticides like Lorsban and Warrior. A full description of this study can be found at the ISU IPM website. Field research was also initiated at Iowa State University to evaluate the compatibility of pesticides used in soybeans and endemic natural enemies. The products being tested included two seed treatments (Gaucho, Cruiser) comprised of unique active ingredients (imidacloprid, thiomethoxam respectively), and two foliar insecticides (Fulfill, Trimax) also comprised of two unique active ingredients (pymetrazione, imidacloprid respectively). These products were selected based on their mode of contact (systemic) and their selectivity for aphids. Results from 2005 can be found at Effects of Reduced Risk-Insecticides on the Soybean Natural Enemy Community on this website. Funding from NCSRP has allowed the laboratory to expand its’ insecticide efficacy program to include impact on natural enemies. This expansion has attracted funding from chemical companies that are interested in registering new, reduced-risk insecticides for use in soybeans. Working with us, they have funded the purchase of a Potter Spray Tower for off-season studies of pesticide impact on natural enemies.

5. Foreign exploration
Further exploration for soybean aphid natural enemies was conducted in China and Korea. During August 2005, USDA-ARS (KRH) and University of Minnesota (GEH) collected soybean aphid parasitoids in the region of Beijing, China. Also, during August - September 2005, USDA-ARS (KAH) surveyed soybean fields in northeastern China in the vicinity of Hohhot and Baotou in Inner Mongolia Province and Harbin in Heilongjiang Province, and south and east of Seoul in Gyeonggi and Chungcheong-nam Provinces of South Korea. Soybean aphids were scattered but relatively easily found in Inner Mongolia, and they were rare in Heilongjiang and in South Korea. Wild soybean was not seen in the vicinity of soybean fields in northern China, but was relatively abundant in Korea so it was also examined for soybean aphid natural enemies. About 1000 mummified aphids containing immature braconid and aphelinid parasitoids were collected and returned to the USDA/ARS quarantine facility in Newark, DE, where the emerging natural enemies will be examined.

Additional collections were made by USDA-ARS in China and Korea in the fall of 2005. The goal of this trip was to collect aphid natural enemies from the soybean aphid’s overwintering host, Rhamnus (buckthorn) species. In Korea, aphids were found on Rhamnus in several locations, but few natural enemies were observed or collected. In China, host plants and aphids were more common and natural enemies were collected from several sites. All told, several dozen aphelinid and braconid mummies and a half dozen predatory fly larvae were returned to the USDA-ARS quarantine at Newark, DE. A return trip to Asia in 2006 is scheduled to collect natural enemies of the aphid early in its invasion of the soybean crop.

Objective 2: Educate growers about the potential of biological control to
manage soybean aphid.
Mahr, Cullen (WI), Ragsdale (MN), O’Neil (IN), DiFonzo (MI), O’Neal (IA), Steffey (IL)

All states reported numerous extension talks, field days and growers meeting where the topic of soybean aphid biological control was discussed with thousands of growers. At WI, an undergraduate student was hired to collect natural enemies from the field, and maintain preserved and live specimens of all life stages in the laboratory. Specimens will be used in biological control workshops and for high quality images for the project website, and PowerPoint slide sets for Midwest Extension specialists. Included are images of parasitoid species in various life stages, and life stage photographs of lacewings, minute pirate bugs, damsel bugs, larvae of syrphid flies, and soybean aphid fungal infection.

This website Soybean Aphid Biological Control website is undergoing final (“beta”) testing prior to release. The site developed and maintained in collaboration with Dr. Julie Meyer of Custom Communication

(Madison, WI), will be a sub-domain of the University of Wisconsin’s “Soybean Plant Health” website (http://www.plantpath.wisc.edu/soyhealth/). An outline of content includes:

• What is biological control?
• An overview of natural enemies, with emphasis on aphids.
• Success of importation biological control vs. aphids.
• Overview and progress of the soybean aphid biological control project.
• Results from other projects.
• Incorporating the benefits of natural enemies into an IPM program for soybean.

Objective 3: Develop a region-wide release program to provide biological control options to soybean producers in the Midwest.
Ragsdale, Heimpel (MN), O’Neil (IN), Gratton (WI), Landis (MI), O’Neal (IA), Tilmon (SD)

In MN, the parasitoid Aphidius colemani was released into field cages to simulate a field insectary approach to propagating high numbers of parasitoid mummies for subsequent dissemination. (Aphidius colemani is an aphid parasitoid that has been repeatedly released in greenhouses and garden setting, and that also attacks soybean aphid.). Cage releases were successful both in producing large numbers of mummies and in suppressing soybean aphids within the cages within 2 generations of the parasitoid. These methods will be adapted to released exotic parasitoids. Sampling for soybean aphid was conducted in all participating states. These data will be used as part of the assessment of the impact of natural enemy releases later in the project.

The necessary “Environmental Assessment (EA) for of one Asian parasitoid, B. communis was completed and submitted to USDA/APHIS for regulatory review. If the application is successful, field releases could commence in summer, 2006. We completed field sampling for soybean aphid as part of the assessment of the impact of natural enemy releases later in the project. Sampling using our suction trap network ended in October. Aphid specimens are being preserved for further study on the identification, phenology, and relative densities of non-target aphids. We are also examining the data for regional trends in soybean aphid dynamics

Edited by Robert J. O’Neil, Purdue University
Participating institutions: Purdue University (R. O’Neil), University of Illinois (K. Steffey), Illinois Natural History Survey (D. Voegtlin), Iowa State University (M. O’Neal), Michigan State University (C. DiFonzo, D. Landis), University of Minnesota (D. Ragsdale, G. Heimpel), South Dakota State University (K. Tilmon), USDA/ARS Beneficial Insect Introductions Research Unit, Newark, DE (K. Hopper, K. Hoelmer), and University of Wisconsin (C. Gratton, D. Mahr, E. Cullen). Overseas collaboration with: Japan - University of Utsunomiya, and Japanese National Agricultural Research Service; China - Chinese Academy of Sciences, and USDA/ARS Sino-American Biological Control Laboratory, Beijing; and Korea - Seoul National University.