NEW ULM — Invasive species — non-native plants, animals and other living organisms that cause or are likely to cause harm to the environment, economy, or human health, may be more costly that most people think.

They cost Minnesotans about $3 billion a year in lost productivity and increased management costs. The national annual cost is about $150 billion, according to a University of Minnesota source presented by Minnesota State University Mankato biology instructor Jordy Veit.

Speaking at a CAST (Community and Seniors Together) program at the New Ulm Community Center Thursday, Veit said some of the most costly invasive species include emerald ash borers, green bugs that feed on ash trees.

“You can see what they did in New Ulm. Many trees were removed here the last couple years,” said Veit.

He said some of the most troublesome invasive plants are buckthorn, leafy spurge, leafy spruce, garlic mustard, and wild parsnip.

“Biological invasions are as costly as natural disasters,” said Veit.

He said garlic mustard is often the only plant that grows to several feet tall with white flowers and stays green during winter.

“It’s a threat in Minnesota, creating a thick mat that shades and out competes native species. It can be controlled by herbicide. Hand pulling must remove the entire root. They should be removed prior to flowering and burned or bagged,” said Veit.

He said leafy spurge is very aggressive, invades pastures, roadside, grassland and prairies and displaces native plants.

“It’s milky sap is toxic to livestock. Mowing can help but repeated herbicide applications need to be done in spring and fall to control it. Leafy spurge beetles over overwhelmingly cost-effective and reducing most infestations,” said Veit.

He said wild parsnip, one of the first plants to green up, can cause severe chemical burns, rashes and blistering. No part of the plant should be touched with bare skin.

Canada thistle is also common with purple leaves, thorns and almost always grows in patches up to five feet tall.

Veit said zebra muscles attach to hard surfaces and can produce 100,000 to 500,000 eggs per year and plug pipes.

“Early detection and rapid response is important,” he said.

Veit said salt cedar trees and shrubs with small, green leaves and pink flowers, found on Minnesota stream banks, can cause allergies due to pollen.

He said goats are effective at eating weeds but they must be used over and over again.

Veit said global warming will cause more invasive species.

“According to the Fifth National Climate Assessment in 2023, the mid western U.S. has about 10 more days above 95 degrees F. and nine fewer zero-degree (0 F) days per year that the 2017-18 assessment,” he said.