Emerald Ash Borer Winning at Peninsula State Park

Those fighting against invasive species share their challenges

Peninsula State Park’s superintendent, Eric Hyde, would love to have the budget and human resources to win more battles against invasive plant species, but a safety issue will have to take priority during the coming months.

Emerald ash borer beetles are killing most of the mature ash trees in the park, and when those trees die, their branches can fall on vehicles, campers, people or park buildings.

“We’ve been working quite a bit to remove all the hazard trees that are dying,” Hyde said.

Park crews and contractors got to work first around the campgrounds and more recently have been removing dead and dying ash trees along roadways. They will need to remove more in the years to come. 

“We’re hoping to get a grant to help remove the more dangerous trees,” he said.

Park staff members have also been working to remove invasive honeysuckle, which can take over in open areas and forest edges, as well as in formerly wooded areas that have been thinned by windstorms.

Workers battling invasive species must often take a triage approach. Door County Invasive Species Team (DCIST) coordinator Samantha Koyen knows this all too well. The DCIST team in recent years has had to slow its efforts to kill plants such as garlic mustard, and instead, this year it focused on eliminating and controlling four less common but also destructive plants: Japanese knotweed, phragmites grass, wild parsnip and teasel.

So how does DCIST prioritize its targets? Koyen says the team is nimble enough to mobilize for its No. 1 priority: eliminating newly arrived destructive species. If they can catch an invader as soon as it’s noticed, the team can have success. 

A year ago, for example, DCIST had success in eradicating an outbreak of porcelain berry – an aggressively spreading vine that looks a lot like wild grape and has Easter-egg pink and light-blue fruit. Porcelain berry can wrap around small trees, and it has suckers that can damage houses.

The team will stop what it’s doing to go after other new arrivals as well, such as black swallow wort. That plant looks a lot like milkweed. Monarch butterflies can be fooled into laying eggs on the plant, but it poisons caterpillars, Koyen said.

Some new arrivals are not easy to eliminate, such as the newly discovered, shallow-burrowing jumping worms, which drastically loosen soil and can adversely affect the roots of trees, grass and wildflowers. Because the team does not yet know how widespread the jumping worms have become in the county and does not have a good way of eliminating them, DCIST emphasizes prevention as the main weapon against the worms. For example, residents who find the jumping worm on their properties are asked to clean their shoes to avoid tracking the worm’s chrysalis onto other properties. 

Koyen said it’s frustrating not to have the resources or grant money to eliminate the more established invasives such as garlic mustard and aquatic zebra mussels and quagga mussels. But that’s the reality.

At Peninsula State Park, Hyde can’t commit enough resources to eliminate garlic mustard, which can rapidly crowd out native wildflowers.

“We can’t get it all,” he said.

However, one local Department of Natural Resources crew does work in designated natural areas within the park to remove garlic mustard, dame’s rocket and other targets that they “deem important.”

At the top of the peninsula, Newport State Park has earned a reputation as a wilderness area and for conditions that make it great for stargazing. However, the land in the park wasn’t always natural. As visitors enter the park from the south, they pass some grassy, weedy areas dotted by low-lying ground juniper. 

“Those were farm fields 50-60 years ago,” Hyde said.

The junipers aren’t bad on their own, but they spread and crowd out other plants. He said he hopes to improve the habitat near the south end of the park and plant more cool-season and warm-season pollinator plants, native grasses and other natural habitat.

“We’re looking at doing some pretty large restoration projects out there,” Hyde said.

Prevention First

With each new invasive species, there is a unifying effort that people can take to help protect Door County’s ecology: prevention. Invasive species can spread in several ways, including hitching rides on equipment to new areas (spotted lantern fly egg sacs attached to vehicles, and for example, and seeds stuck on shoes and pet fur); in water containers (zebra mussels’ and quagga mussels’ larvae in coolers and boat props); in firewood (emerald ash borer); and on a pet or ornamental plant (yellow iris, bishop’s weed). 

Prevention is relatively simple and helps to address the numerous pathways that new invaders use: 

• Inspect all equipment and furry friends, and clean all debris off them. 

• Don’t move anything containing suspected invasive species; keep it on-site. 

• Plant only native plants, and use locally sourced planting materials. 

• Properly dispose of material that contaminated with invasives (landfill and/or solarize and landfill). 

• Stay on hiking trails. 

• If possible, control invaders.

Source: Door County Invasive Species Team,

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