NCSRP soybean aphid importation biological control

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Pest: Aphids

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Aphid natural enemies

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NCSRP Soybean Aphid Biological Control project

Field cages were set up in aphid-infested fields for release of the soybean aphid parasitoid, Binodoxys communis.
Photo credit: University of Minnesota

Parasitic wasps (parasitoids) are largely missing from soybean aphid in North America but are important in suppressing soybean aphid in Asia, where it is only a minor pest. The North Central Soybean Research Program, along with state checkoff boards and the USDA, has invested in a biological control effort to establish one or more of these species to attain long-term suppression of soybean aphid, as is seen naturally in Asia. A major advantage of this form of biological control is that once it is established, it is free of charge to growers, making the cost/benefit ratio potentially very favorable.

Examples of a successful strategy

This strategy, called classical biological control, has been highly successful in agriculture. For example, the cereal leaf beetle and the alfalfa weevil, both non-native insects, are now effectively suppressed by biological control and rarely have to be managed by growers. The goal is not to eradicate the aphid, but to establish a new equilibrium between the aphid and it's natural enemies, thus managing the pest to a level where damage is minimal.

An aphid parasitoid, Binodoxys communis adult
Photo credit: Kelley Tilmon, South Dakota State University

A missing link: aphid parasitoids

The first challenge was to explore Asia for natural enemies of the soybean aphid that were missing in North America. Because parasitic wasps play such an important role in suppressing the soybean aphid in Asia, and are largely missing in the U.S., several promising species were brought to this country and put through a series of safety tests. The identification, testing, and release of a new biological control organism is a complicated process that takes years.

The first aphid parasitoid to be granted a release permit, Binodoxys communis, was released in the summer of 2007 and 2008. At this time, it seems that Binodoxys has not establshed. However, permits are pending for two other promising species that may be better able to handle Midwest winters. And much has been learned about the importation and release process.

Steps to a successful introduction of beneficial insects

1. Climate / Habitat Matching
From 2001 to 2006, entomologists from University of Minnesota, the Illinois Natural History Survey, Purdue, and the USDA worked with Asian cooperators to identify suitable areas for collecting parasitoids. These areas had both soybean production and buckthorn, and were a climate match for important soybean production areas in the United States. Climate-matching increases the likelihood of finding insects adapted to local conditions, increasing the success of an introduction.

2. Foreign Exploration
The USDA Agricultural Research Service worked with scientists in China, South Korea, and Japan to collect natural enemies of soybean aphid. Parasitoid collections were made from both soybean and buckthorn, at different times of the year. These insects were shipped back to U.S. quarantine facilities.

3. Importation
It was an administrative and logistical challenge, requiring many permits, to move live insects from foreign countries to the United Sates. Parasitoids have a short life cycle; the insects must reach the U.S. from Asia in a matter of days, or die in transit.

4. Rearing and Testing in Quarantine
Back in the U.S., parasitoids were kept in quarantine at the USDA Beneficial Insect Research Lab in Delaware or at a new MAES/MDA Facility at the University of Minnesota in St. Paul. It is very labor intensive to rear plants and keep aphid colonies to rear the wasps.

Each parasitoid is tested for how effective it is at using soybean aphids as a host. It is important not only to release an effective natural enemy, but also one with a narrow host range that will not disrupt non-target aphid species.

5. Release Permits
Once efficacy and host range data are complete, more permits are needed from the U.S. and Canadian governments to make field releases. Permits for the release of the first parasitoid, Binodoxys communis were finalized in the spring of 2007.

6. Field Introductions
The first field releases of Binodoxys was done in IA, ,IL, IN, MN, SD and WI in 2007 and in IA, IN, MN, MI, SD, and WI in 2008. Research entomologists are determining the parasitoid's survival and efficacy. Permits for two more species are pending.

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