Environment
2:58 pm
Thu February 24, 2011

Beekeepers' favorite invasive

Researchers from Michigan State University are trying to control an invasive plant called spotted knapweed. They’ve released two foreign beetles that eat the plant on small plots of state land.

Knapweed spreads a carpet of purple flowers over old farm fields and alongside roads in mid-summer.

But as The Environment Report's Bob Allen discovered, beekeepers rely on those flowers for making honey.

Spotted knapweed tends to dominate any landscape where it takes hold. Its roots send out a chemical substance that kills nearby plants.

But researchers in several states think they’ve found a way to keep it in check. They’ve released two species of tiny European weevils.

One attacks knapweed’s roots, the other eats its seeds.

Doug Landis is a bug specialist at Michigan State University. He says in some test plots the bugs have knocked knapweed back as much as 80%.

“These insects don’t eliminate knapweed. But they can reduce its density to the point where it becomes a more manageable part of the plant community.”

Knapweed is found in every county in Michigan but especially in sandy soils. And land managers want to get rid of it because it crowds out native wildflowers and grasses that supply food and shelter to a wide variety of insects, birds and other wildlife.

But beekeepers say the plant has a lot of value for them. They even have a more poetic name for it... star thistle. And they say it produces a light, mild, pleasant tasting honey that puts northern Michigan on the map.

“It’s one of the best honeys in the country.”

Kirk Jones runs Sleeping Bear Apiary in Benzie County.

He says his star thistle honey is in demand in stores and restaurants across the country.
And it’s the only source of surplus nectar available for his bees late in the season.

“And without that source of nectar to make honey we wouldn’t be able to keep bees here. And then there would be a spin-off of not having a robust bee population for everybody…to pollinate their flowers to make food.”

Part of the MSU research is to replace star thistle with a mix of native wildflowers.

And Doug Landis at Michigan State thinks it won’t hurt the bee business if some fraction of knapweed is replaced.

“I believe consumers would be very happy to buy a native Michigan wildflower honey whether it says star thistle on it or not.”

But beekeeper Kirk Jones doubts that wildflowers will ever be abundant enough to replace the nectar flow of star thistle.

He says the plant has adapted here for more than a hundred years and it doesn’t makes sense to interfere with that balance now.

“There may be good intentions. But I think it’s probably of dubious value to try to return old farmland to some point in time in the past.”

But researchers say it likely will take a decade or more for the weevils to control knapweed on a few of the thousands of acres covered with the plant.