Herbicide-Insect Synergy Studied for Leafy Spurge Control
By Steve Merritt
TEAM Leafy Spurge Technology Transfer Specialist

SIDNEY, Montana — Capitalizing on the synergy between herbicides and biocontrol agents could be the key to providing affordable, long-term leafy spurge control, says a professor of Plant Sciences at North Dakota State University.

Rod Lym has researched leafy spurge control with herbicides for nearly 20 years and is now the lead investigator in two herbicide and biocontrol agent projects for the USDA-Agricultural Research Service’s TEAM Leafy Spurge. Lym says years of experience with the formidable noxious weed has convinced him that no one control tool will win the war against leafy spurge.

"It’s pretty clear that Integrated Pest Management is the future of leafy spurge control," he said. "There is no single answer, and that’s why we’re participating in TEAM Leafy Spurge — it focuses on combining the best elements of the tools we have at our disposal."

One of Lym’s TEAM Leafy Spurge projects uses herbicides to promote biocontrol insect establishment; the other evaluates new herbicide control technologies. Lym is especially optimistic about demonstrating the beneficial relationship between herbicides and biocontrol insects.

"Insects work well in some places, but don’t seem to do much in others," he said. "Our study site is a classic example — despite numerous releases made during the past few years, the flea beetles never established large enough populations to provide effective leafy spurge control."

The project builds on past research showing that leafy spurge control is enhanced when herbicides and biocontrol agents are used in tandem.

"We believe herbicides can be used to help the flea beetles become established more quickly, and that’s what we’re trying to demonstrate," Lym said. "If we can help the flea beetles build large populations, they can then become a factor in providing low-cost, self-sustaining leafy spurge control on a long-term basis."

The herbicide-only study is evaluating some "old favorites" as well as several new compounds recently labeled for use on leafy spurge. Included in the study are Tordon, Tordon plus 2,4-D, Banvel, Roundup, Landmaster BW, Krenite and Plateau.

"We’ve used a variety of rates with both spring and fall applications to demonstrate which herbicides will provide the best control and at what cost," Lym said. "We’re particularly interested in three things: Demonstrating which herbicides are the most cost-effective, which ones provide the best long-term control and which ones are the most appropriate for use in environmentally sensitive areas, such as in riparian areas, around water and livestock and near trees."

Ranchers, landowners and land managers will get a chance to see results of both studies next spring and summer.

"We’ll have tours of the demonstration sites so people can see first-hand the kinds of results that were produced," Lym said. "All of the sites will have signs to provide information on the types of herbicides used and the rates and costs of treatment. It’s going to be an extremely informative opportunity for ranchers and land managers who have problems with leafy spurge."

TEAM Leafy Spurge is a five-year IPM research and demonstration project funded and led by the USDA-ARS in partnership with the USDA-Animal & Plant Health Inspection Service. Its goal is providing landowners and land managers with proven leafy spurge control techniques based on IPM strategies.

TEAM participants include the U.S. Forest Service, National Park Service, Bureau of Land Management; land grant universities, including Montana State University, North Dakota State University, South Dakota State University and the University of Wyoming; county weed supervisors, ranchers and land managers.

For more information on TEAM Leafy Spurge, biocontrol of leafy spurge or Integrated Pest Management, contact Chad Prosser at 406-433-9403 (cprosser@sidney.ars.usda.gov). For more information on leafy spurge herbicides, contact Rod Lym at 701-231-8996 (lym@plains.nodak.edu).