WOOSTER, Ohio – An exotic invasive shrub, introduced in the 1800s as a garden plant, is being studied to demonstrate how its presence has a cascading damaging effect on natural flora and fauna, agriculture and public health.
Ohio State University entomologists are collaborating with Michigan State University and Iowa State University in a three-year research project to determine the distribution of buckthorn throughout Michigan, Ohio, Minnesota and Iowa. The study, "Common Buckthorn as a Keystone Invader in Agricultural Landscapes," is supported by a $494,000 Agricultural and Food Research Initiative grant funded by the U.S. Department of Agriculture.
Buckthorn is the link in a chain of invaders that has a negative impact on the ecosystem. Not only does the shrub choke out native plants, but it is also the overwintering host for the soybean aphid, an invasive sapsucker that damages soybeans and spreads viruses to vegetable crops. In turn, the soybean aphid is food for the multi-colored Asian ladybeetle, an invasive insect that damages grapes, outcompetes native ladybeetles for food and habitat, and finds its way into the homes of many Ohioans.
"Without the invasion of buckthorn, it's probably unlikely that the soybean aphid would have established itself, and as a result, we'd have less impacts on crops and fewer issues with the multi-colored Asian ladybeetle," said Andy Michel, an OSU entomologist with the Ohio Agricultural Research and Development Center.
By determining how much buckthorn is spread across the four states, researchers hope to learn more about how buckthorn influences aphid dispersal and populations of the multi-colored Asian ladybeetle. The goal, ultimately, is to identify best management practices for buckthorn to best control both insects.
One aspect of the study is to determine if soybean aphids found in Ohio are originating from buckthorn established in Ohio, or are migrating from more northern latitudes, such as Michigan.
"We are collecting aphids from Ohio and Michigan and using genetic markers to determine if aphids plucked from Ohio soybean fields are genetically similar to aphids being found on buckthorn in Ohio, or if perhaps they are originating from other locations, like Michigan," said Michel, who also holds an Ohio State University Extension appointment.
The outcome of that work, said OARDC entomologist Mary Gardiner, is managing the soybean aphid by going back to the overwintering source.
"If we determine that aphid colonization in Ohio is localized, that is, if aphids in soybean fields are originating from local buckthorn establishments, then we can manage the aphid by eradicating the buckthorn within the local area," said Gardiner, who also holds an OSU Extension appointment. "If we determine that aphids are migrating from more northern locations, then we can conclude that intensive buckthorn management in Ohio may not be as effective for soybean aphid control, and that aphids can migrate long distances and their management may be more difficult."
Other objectives of the research include:
• Determining if the density of buckthorn within the landscape surrounding soybean fields influences the likelihood and timing of aphid infestation.
• Examining whether aphid populations in areas with high density of buckthorn serve as a source of aphids in areas lacking significant buckthorn establishment.
• Determining if soybean fields in buckthorn-infested landscapes colonized early in the season with soybean aphid are more likely to attract the multi-colored Asian ladybeetle.
• Studying whether buckthorn surrounding vegetable cropping systems increases the likelihood of virus transmissions from the soybean aphid to the crops.
As part of the outreach and education objectives of the project, researchers will be looking to Ohio citizens to aid in data collection.
Beginning in the spring, Gardiner will launch Buckthorn Watch, a citizen-science program where residents volunteer to identify buckthorn establishments in their area, and collect soybean aphids and multi-colored Asian ladybeetles for analyses. A Web site explaining the program will be available soon. For more information, contact Mary Gardiner at (330) 263-3643 or e-mail firstname.lastname@example.org.
"We hope that the public will look at invasive species as more than just damaging to the landscape and realize that they tend to work together to create a synergistic negative impact across multiple environments and situations," said Michel. "The reason why the system with buckthorn, the soybean aphid and the multi-colored Asian ladybeetle works so well is because of evolutionary history – all three invasives are from Asia. It's like we've taken that entire system and transplanted it here in the United States."