Early beetle harvestIf you want to collect flea beetles to control leafy spurge, you’ll need to start earlier than usual this year. Normally, the bugs are collected from the middle of June to early July across the region. Collection — which needs to occur before the insects begin laying their eggs — should start roughly two weeks earlier this year because of the mild winter and early spring, officials say.
By: Jonathan Knutson, Agweek
If you want to collect flea beetles to control leafy spurge, you’ll need to start earlier than usual this year.
Normally, the bugs are collected from the middle of June to early July across the region. Collection — which needs to occur before the insects begin laying their eggs — should start roughly two weeks earlier this year because of the mild winter and early spring, officials say.
“We’re ahead of normal,” says Monika Chandler, biological control coordinator for the Minnesota Department of Agriculture. She began collecting flea beetles in late May.
Leafy spurge, one of the region’s most dangerous weeds, is toxic to cattle and can completely take over big areas of land. The plant reproduces through both an extensive, deep root system and explosive seed capsules that throw seed as far as 15 feet from the parent plant.
Leafy spurge can be controlled effectively with chemicals, particularly in cropland. However, applying herbicides to pastureland usually isn’t cost-effective, officials say.
The weed also can be controlled with the use of beetles imported from Europe. North Dakota, South Dakota, Minnesota and Montana all have long-in-place programs that promote the use of flea beetles against leafy spurge.
The beetles are collected with sweep nets in fields where the beetles are well established. It’s important not to remove too many of the bugs from one site, says Janet Knodel, North Dakota State University Extension Service entomologist.
After they’re collected, the beetles are taken to, and released in, other areas where leafy spurge is a problem.
How the bugs work
South Dakota State University Extension has this description of how the beetles work:
Typically, three to five years are needed for the bugs to become established and cut into leafy spurge infestations. While adult beetles will do some feeding on plants, it’s the larval form of the insect that lethally injures leafy spurge plants. The newly hatched larvae will feed on the leafy spurge roots and root hairs, hurting the plants’ ability to utilize water nutrients. This weakens the plants, making them vulnerable to disease and winterkill.
The beetles do kill leafy spurge plants, Knodel says.
However, leafy spurge can return and re-establish itself in areas where the beetles did their work and died off, she says.
Beetles will need to be reintroduced into those areas for the insects to once again control spurge, she says.
Leafy spurge infests about 850,000 acres in North Dakota, 750,000 acres in Montana and 275,000 acres in South Dakota, according to government websites and officials in the three states.
Chandler says she’s uncertain of the number of infested acres in Minnesota. She also says the number has dropped sharply because of the use of biological controls.
The downside of fewer spurge-
infested acres is that there are also fewer opportunities to collect beetles, she says.
Using beetles also has cut into leafy spurge acres elsewhere in the region, officials say.
“The beetles have really helped control leafy spurge,” says Dave Burch, state weed coordinator for the Montana Department of Agriculture.
Where to get the beetles
Here’s a state-by-state look at where landowners can learn more about collecting the beetles:
• North Dakota — To find collecting sites for leafy spurge flea beetles, contact your local county extension agent or weed control officer. A listing of the weed control officers by county can be found on the North Dakota Weed Control Association website: http://ndweeds. homestead.com/10_ County_City_ Weed_Boards_Directory.pdf.
• South Dakota — To get your name on the list to be notified of area collections, contact Ron Moehring (605-773-3299), Brenda Sievers (605-353-6700), or Mike Stenson (605-773-5645) with the South Dakota Department of Agriculture or Darrell Deneke, SDSU Extension, (605-688-4595).
• Montana — Start with the Montana Weed Control Association, www.mtweed.org.
• Minnesota — Information on leafy spurge in the state: www.mda.state.mn. us/plants/badplants /leafyspurge.aspx. Private landowners interested in biocontrol for leafy spurge should contact their county agricultural inspector. More information: www.mda.state .mn.us/en/plants/pesmanagement/weedcontrol/cailist.aspx.