With permission from government officials, the university team pursued an integrated approach that combined highly targeted herbicide treatments with a natural biocontrol - a tiny flea beetle (Aphthona spp.) that enjoys feasting on leafy spurge leaves and roots.
"We applied the herbicide once in the fall, when the orchid was at the end of its annual blooming cycle and less likely to be injured," Lym said. "That gave us a way to knock back the weed while the flea beetle population was getting established."
Researchers found that their integrated program controlled 99 percent of the leafy spurge across the acres treated, without damaging the reproduction or development of the orchid itself. Their approach has tipped the balance back towards the natural ecosystem in the Sheyenne National Grassland, where native vegetation is now being reintroduced and the prairie orchid is better able to grow.
The same experience has begun to play out across North Dakota, says Lym, who is a 30-year veteran of the leafy spurge wars. He reports that prior to 1995, the number of infested acres in the state doubled every 10 years. Thanks to the combination of herbicides and biocontrols, the trend has now reversed. Half of the 1.6 million acres overrun by leafy spurge have been reclaimed.
"The right mix of weed control tools is helping us win the battle," Lym says. "We're able to manage leafy spurge over the long-term and reclaim our natural ecosystems so that the prairie orchid and other native plants can thrive."
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