1) Project title: Soybean aphid research.

Investigators: Robert J. O’Neil, Claire Rutledge, Ho Jung Yoo, Casey Butler

Contact: Robert J. O’Neil (bob_oneil@entm.purdue.edu)

Project description: Our soybean aphid (SBA), Aphis glycines Matsumura (Homoptera: Aphididae), research program focused on study of aphid-primary host relationships; identification of relationships between soybean production practices and aphid dynamics; and endemic natural enemy impact on aphid dynamics.

1. Aphid-primary host relationships: A collaborative study with the Illinois Natural History Survey and Iowa State University is being used to determine the (primary) host suitability of 10 rhamanceous taxa, the overwintering capability of the aphid, and its reproductive potential on its primary host(s). In a “choice” cage study conducted in Illinois, two species of Rhamnus, R. cathartica and R. alnifolia, were confirmed as hosts; defined as plants that that aphid would deposit overwiintering eggs. This was the first identification that R. alnifolia could serve as an aphid host plant. This study is being repeated in 03-04. An additional study to examine gynoparae, oviparae and egg production on wild R. cathartica in Indiana, confirmed the aphid does use this host in the wild, but that overwintering survival was extremely low. Fall aphids have also been found on R. frangula and R. alnifolia in the wild, however the production of eggs and overwintering survival has not been confirmed. A laboratory study to examine no-choice host selection and oviparae and egg production is currently being conducted.
2. Soybean production practices: Production practices on aphid population ecology were studied for the second year in blocks of soybeans planted at 4 different dates. Aphid population densities were not affected by plant age (planting date) with densities reaching similar levels on older plants (earlier-planted dates) and younger plants. Additionally, no significant effect of plant age was found for either aphid reproduction or population growth. A statewide survey of aphid densities showed that the northern one-half of the state was heavily infested (>>200 aphids/plant), and insecticides were commonly applied. An initial analysis of aphid impact on soybean production is on-going. No consistent pattern of agronomic factors (e.g., planting date, variety, group) and aphid dynamics has been noted.
3. Endemic natural enemies: The impact and ecology of endemic natural enemies were intensively studied in a field in Tippecanoe county and extensively examined using data from the statewide sampling effort (above). As in past years, the predominate natural enemy was Orius insidious, although other predators, particularly Harmonia axyrides were abundant later in the season. There was little evidence of parasitism but fungal disease epidemics were relatively common. Field trials examining the influence of aphid density and between-plant dispersion patterns showed a significant effect of density, but relatively minor effect of spatial dispersion. Predators present in the field before aphids arrive can have a significant effect on subsequent aphid densities, however this impact is influenced by the presence of alternative prey such as whiteflies and thrips. Further studies on predation, prey density, plant size, predator and prey dispersion patterns, and alternative prey are planned. A simulation model of predator-prey dynamics in soybeans is under construction. Life history measurements of O. insidiosus fed soybean aphid have been initiated.

2) Project title: ACORN- A Web-based Alternative Control Outreach Network for Home Gardeners.

Investigators: Clifford S. Sadof, Robert J. O’Neil, and Farah Heraux

Contact: Robert J. O’Neil (bob_oneil@entm.purdue.edu)

Project description: We developed a web-based tool to complement day-long workshops and to facilitate development of a network of home gardeners who are actively experimenting with pesticide alternatives. These tools include solicitation and execution of clearly defined experiments, data collection and summary, as well as a bulletin board to facilitate communication. We reached ca. 20% of Master Gardeners in the two-states (IL & IN), and surveys showed that Master Gardeners involved with the ACORN program reduced pesticide use by 25% while increasing their use of biological control by up to 20%. The web site (www.entm.purdue.edu/acorn/) has received over 10,000 hits since inception ca. 18 months ago. An instructors manual was developed to allow other Extension specialists to hold biological control workshops modeled after the ACORN program. Thus far, specialists from 19 states and British Columbia, Canada have requested copies of the manual.

3) Project title: Garlic mustard research

Investigators: Robert J. O’Neil, Kimberly Rebek

Contact: Robert J. O’Neil (bob_oneil@entm.purdue.edu)

Project description: Garlic mustard, Alliaria petiolata, is an exotic biennial herb that invades forest communities throughout eastern North America. Researchers in Switzerland are investigating several natural enemy species for use as potential control agents. In the US, several groups (Cornell, University of Illinois, and others) have studied various aspects of garlic mustard ecology in invaded habitats. Our research has investigated the ecological aspects of the plant pertinent to the biological control agents under investigation, including studies in garlic mustard life history, simulated injury and winter mortality. We found relatively little impact of garlic mustard density on plant survival, but a considerable effect on its reproduction. Simulating damage to the plant also affected reproduction more than survival. Taken together, natural enemy selection should favor those natural enemies that impact plant reproduction rather than survival.

4) Project title: Conservation biological control of euonymus and pine needle scales.

Investigators: Cliff. Sadof, Eric Rebek and Larry Hanks U. of Il.

Contact: Cliff Sadof (cliff_sadof@entm.purdue.edu)

Project description: We established Euonymus fortunei and Pinus sylvestris plots(L.) plots (1 m2) surrounded by four flowering plant species (one per plot border) in three levels of floral density: no flowers (mulch only), low flower density and high flower density in the fall of 1999. During the summer of 2001, we found increases in parasitism and natural enemy abundance in flowering versus mulch plots. However, flower density did not significantly affect these parameters. These results suggest that planting flowers with may increase the potential for successful biological control of armored scale in landscapes. Information was used to produce a web site on the biological control of soft and armored scales for NCR-125: http://www.cips.msu.edu/ncr125/GuideScales.htm. Related studies conducted in 2001 and 2002 developed a method for assessing impacts of environmental conditions on parasitoid populations. These results were published in the April 2003 Journal of Economic
Entomology. http://esa.edoc.com/economic/v96n2/v96n2p446.pdf

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Rebek, E. and C. Sadof. 2003. Effects of Pesticide Applications on the Euonymus Scale (Homoptera: Diaspididae) and Its Parasitoid, Encarsia citrina (Hymenoptera: Aphelinidae. J.Econ.Entomol.96:446-452.

Sadof, C. S., R. J. O’Neil, F. M. Heraux, and R. N. Wiedenmann. 2004. Reducing insecticide use in home gardens: effects of training and volunteer research on adoption of biological control. HortTechnology (in press).

Voegtlin, D., R. J. O’Neil and W. Graves. 2004. Tests of suitability of overwintering hosts of Aphis glycines: identification of a new host association with Rhamnus alnifolia L’Hér. Annals Ent. Soc. Amer. (Accepted, in revision at journal).

Rutledge, C. E., R., J. O’Neil, T. B. Fox and D. A. Landis. 2004. Soybean aphid predators and their use in IPM. Annals Ent. Soc. Amer. (Accepted, in revision at journal).

Wiedenmann, R. N., C. S. Sadof, R. Diaz, and R. J. O’Neil. 2004. Ground beetle assemblages in mulched and unmulched garden plots. Submitted to J. Kansas Ent. Soc. (Accepted, in revision at journal).

Heimpel, G. E., D. W. Ragsdale, R. Venette, K. R. Hopper, R. J. O’Neil, C. Rutledge and Z. Wu. 2004. Prospects for importation biological control of the soybean aphid: anticipating potential costs and benefits. Annals Ent. Soc. Amer. (Accepted, in revision at journal).

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