Biocontrol: Leafy spurge, flea beetles, Boy Scout camp (ND)

[RememberSchiff]

July 7, 2022, North Dakota:

Leafy spurge is an invasive, fast spreading noxious weed which cattle will not graze.

The plant also contains a toxic substance that serves as an irritant, emetic and purgative when consumed by livestock.  It has caused death in cattle, sheep and loss of hair and inflammation on the feet of horses.  However, sheep and goats can graze Leafy spurge as part of their diet, as a form of cultural control of the plant.

Every summer for more than a quarter century, Merlin Leithold, executive secretary of the North Dakota Weed Control Association and Grant County weed control officer, has held a flea beetle field day along the south shore of Lake Tschida at the Boy Scout camp site.

Some 100 landowners brought cloth nets in the shape of a cone to sweep back and forth through the fields of spurge plants, collecting tiny orange flea beetles to control leafy spurge at their ranches. It was still wet out from rain the night before, so net sweepers had to wait for the leaves to dry so sweeping could be successful. In addition, wet flea beetles usually do not survive.

“We swept for and collected 545,000 flea beetles at this year’s field day. We put about 3,000 flea beetles in each paper bag and were able to hand out 185 bags for landowners to release on their properties,” he said. “They put the bags in their coolers and took them home to their ranches. It was a good day.”

“Flea beetles only eat leafy spurge, nothing else, and leafy spurge continues to be one of North Dakota’s most difficult-to-control noxious weeds,” Leithold said.

What is unusual about the Boy Scout camp site in Grant County is that it is the only site in the state that has been producing flea beetles every year for 26 years.

“Most field days on a site have a duration of five years at the longest, but this site could be considered the longest running field day on the same site in the nation,” he said. “If records were kept, it would probably be a U.S. record.”

Leithold is not sure why the Boy Scout camp site continues to produce flea beetles long after other sites have to be closed and moved to another leafy spurge area, but he suspects it has something to do with ants. Female flea beetles lay eggs in the spring, and ants are natural predators of the eggs.

“I think there’s just enough ants there to keep the population of flea beetles down to where they don’t completely overtake the leafy spurge at the site,” he said.

Using the flea beetles for biological control, as part of an integrated pest management plan, has proven to be an effective tool in combatting leafy spurge infestations, according to the North Dakota Department of Agriculture.

A few years ago, Boy Scout officials wanted to build a covered picnic table area at the camp for the boy scouts. When they found out that the area was used for a flea beetle field day, they built it where the county could utilize it for the field day.

“It is really a nice area for a flea beetle field day,” Leithold said.

Near the covered picnic area, Leithold builds a collection area with jars underneath so ranchers can dump the beetles out when their nets are full. Then, they can return to sweeping and gathering more flea beetles.

At the end of the day, Leithold, along with Martin, and other sorters, take out the flea beetles and place them in paper bags with a bit of spurge to feed on and staple the top.

More at sources:

https://www.agupdate.com/farmandranchguide/news/crop/flea-beetle-field-day-offers-bio-control-solution-for-producers/article_cced0d20-15be-11ed-949a-5f8cead6338f.html

https://www.ag.ndsu.edu/publications/crops/integrated-management-of-leafy-spurge

https://library.ndsu.edu/ir/bitstream/handle/10365/3098/1887th90.pdf?sequence=1

https://beef.unl.edu/beefwatch/2020/leafy-spurge-0