Local experts talk about invasive species

TR PHOTOS BY LOGAN METZGER Poison-hemlock has white flowers that grow in small erect clusters and has a hollow stem marked with small purple spots. It is very toxic and sheep, cattle, swine, horses, and other domestic animals are poisoned by eating small amounts of green or dried plant. It is also extremely poisonous to humans.

Though they may not be on everyone’s mind, invasive species surround everyone. Marshall County has an almost uncountable amount of invasive species of plants and animals. Here are 10 to know about.

An “invasive species” is defined as a species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health, according to the USDA website.

1. Emerald ash borer

Emerald ash borer is an exotic beetle that was discovered in southeastern Michigan near Detroit in 2002. The adult beetles nibble on ash foliage but cause little damage. The larvae feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients.

Donald Lewis, extension entomologist at Iowa State, said cases of the emerald ash borer have been confirmed in 2018 north of Le Grand in Marshall County and in Marshalltown. It has also been confirmed in 65 other counties in Iowa.

TR PHOTOS BY LOGAN METZGER Wild parsnip can grow up to 5 feet tall and has hollow, grooved stems that are hairless. Small, yellow flowers are clustered together in a flat-topped array. Wild parsnip sap contains chemicals which can cause a severe burn within 24 to 48 hours of coming in contact with it.

Emerald ash borer spreads quite slowly on its own, only being able to fly short distances, but humans spread the emerald ash borer through infested firewood.

“A load of infested firewood in the back of pickup truck traveling at 55 miles per hour down the road can have the emerald ash borer two states over by the end of the day,” Lewis said.

As of October 2018, it is now found in 35 states, and the Canadian provinces of Ontario, Quebec, New Brunswick, Nova Scotia and Manitoba, according to the Emerald Ash Borer Information Network website.

2. Wild parsnip

Wild parsnip can grow up to five feet tall and has hollow, grooved stems that are hairless. Small, yellow flowers are clustered together in a flat-topped array.

Dana Holland, district conservationist at the Natural Resources Conservation Service, said wild parsnip is found within ditches and along bike trails. It is extremely pervasive, grows fast, and produces lots of seeds which means it spreads very fast.

“If you touch these and get the sap on your skin, it will burn your skin,” Holland said.

Wild parsnip sap contains chemicals which can make skin more vulnerable to ultraviolet light. Brushing against or breaking the plant releases sap that, combined with sunlight, can cause a severe burn within 24 to 48 hours. This reaction can also cause discoloration of the skin and increased sensitivity to sunlight that may last for years.

To protect from wild parsnip do not touch any parts of the plant with bare skin and wear gloves, long-sleeved shirts, pants, boots and eye protection if working near the plant to prevent skin contact with the sap. Synthetic, water-resistant materials are recommended.

If contact with sap occurs wash the affected area thoroughly with soap and water, and keep it covered for at least 48 hours to prevent a reaction. If a reaction occurs, keep the affected area out of sunlight to prevent further burning or discoloration, and see a physician.

3. Bush honeysuckle

Bush honeysuckles are invasive deciduous shrubs that grow up to 20 feet tall. There are three species of bush honeysuckle common in the region including tartarian (Lonicera tatarica), Morrow’s (Lonicera morrowii) and Amur (Lonicera maackii).

Adam Janke, extension wildlife specialist at Iowa State, said bush honeysuckle is problematic because they can leaf out before almost any other woody plants can and they can also maintain their leaves longer than almost any native plants. These abilities cause the bush honeysuckle to suck up a lot of the light before it reaches any other plants in the underbrush of forested areas causing them to die out.

“This changes the diversity in the forest,” Janke said. “And with less plant diversity there is less insect diversity and this creates a lack of food items for other animals in the forest to eat.”

Bush honeysuckle poses no direct threat to humans, but can hinder the growth of new trees for lumber production.

4. White nose syndrome

White nose syndrome is a fungal disease caused by the fungus Pseudogymnoascus destructans. This disease only affects bats and is called white nose syndrome because it sometimes looks like white fuzz on the nose and other hairless parts of bats, including wings.

Janke said this has caused massive bats to die throughout the country and it was first found in the U.S. in New York in 2006. In Indiana bat populations have declined 70-90 percent since 2011 due to white nose syndrome.

Affected species of bats in Iowa include northern long eared bats, little brown bats, and tri-colored bats, and has put the northern long eared bat on the endangered species list, Janke said.

5. Poison-hemlock

Poison-hemlock grows throughout the United States, introduced in the 1800s as a garden plant. It is very toxic and sheep, cattle, swine, horses and other domestic animals are poisoned by eating small amounts of green or dried plant. It is also extremely poisonous to humans.

Poison-hemlock has white flowers that grow in small erect clusters and has a hollow stem marked with small purple spots.

Poison hemlock quickly colonizes disturbed habitats such as roadsides, old fields, fencerows and ditches. In natural areas it can displace native plant species and prefers riparian habitats. It has been spotted in Marshalltown by Fisher’s Community Center.

Mike Stegmann, Marshall County Conservation director, said it can be found in any location you could think of.

Poison hemlock was the plant used to kill Socrates in 399 B.C.

6. Garlic mustard

Garlic mustard originates from Europe and parts of Asia and entered the U.S. about 1870. Garlic mustard has the potential to form dense stands that choke out native plants in the understory by controlling light, water, and nutrient resources.

While it is usually found in the undergrowth of disturbed woodlots and forest edges, it has the ability to establish and spread even in pristine areas. This spread has allowed it to become the dominant plant in the undergrowth of some forests, greatly reducing the diversity of all species in the area.

Stegmann said garlic mustard can take over an entire forest floor easily and choke out other plants.

Garlic mustard is not harmful to humans and can be ingested by humans. Leaves can be eaten but once the weather gets hot, the leaves will taste bitter. Flowers can be chopped and tossed into salads. The roots can be collected in early spring and again in late fall, when no flower stalks are present. In the fall the seed can be collected and eaten.

7. Japanese knotweed

Japanese knotweed was introduced into the U.S. from Eastern Asia as an ornamental in the late 1800s. The plant, which can grow from three to 15 feet tall, has bamboo-like stems and is sometimes called Japanese bamboo.

Japanese knotweed spreads rapidly, forming dense thickets that crowd and shade out native vegetation. This reduces species diversity, alters natural ecosystems and negatively impacts wildlife habitat.

The ground under knotweed thickets tends to have very little other growth. This bare soil is very susceptible to erosion, posing a particular threat to riparian areas. Once established, populations of Japanese knotweed are extremely persistent and hard to eradicate.

8. Japanese beetle

The Japanese beetle is an invasive plant pest that was first introduced to eastern North America from Japan in 1916.

Japanese beetles can significantly damage landscape plants, ornamental plants, fruit and vegetable gardens, orchards and other agricultural crops. Japanese beetle larvae feed on the roots of turf grass and other plants while adults attack the flowers, foliage and fruit of more than 250 plant species, including roses, blueberries and grapevines.

Stegmann said they are a big cause of local defoliation and usually come out mid- to late summer.

Japanese beetle is not a risk to human or animal health or food safety, but heavily damage crops and other plants.

9. Tree of heaven

Tree of heaven is a rapidly growing deciduous tree native to both northeast and central China, as well as Taiwan and was first seen in the U.S. in 1784.

Tree of heaven crowds out native species decreasing diversity within its growing area. It also damages pavement and building foundations in urban areas.

Tree of heaven can affect human health. The tree is a very high pollen producer and a moderate source of allergy in some people.

10. Brittle naiad

Brittle naiad is a rooted, submersed aquatic plant with a bushy appearance. Brittle naiad is native to Europe, western Asia and northern Africa and was confirmed in the U.S. in 2010.

Thick infestations of brittle naiad can inhibit the growth of native aquatic vegetation and make fishing and recreational boating difficult. Brittle naiad plants are extremely brittle and have an increased risk of breaking apart, increasing the likelihood for it to spread via boats, waterfowl and water movement.

Stegmann said brittle naiad has been spotted in Sand Lake and Green Castle, but has not become a problem yet.


Contact Logan Metzger at

641-753-6611 or



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