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Officials wary of invasive species in North Dakota

Stutsman County is under attack by land, water and air by hordes of foreign invaders.

Invasive species threaten the balance of ecosystems they encroach upon. The invaders compete with native species for food, destroy habitat and often reproduce at higher rates than native species.

The most common and easily-identifiable invasive species in the county are the noxious weeds absinthe wormwood, Canada thistle and leafy spurge. Lindsey Novak, Stutsman County’s North Dakota State University Extension agent, said these species can easily be controlled with chemical sprays, and sheep and goats will actually graze on leafy spurge. Leafy spurge can grow to be 3 to 4 feet long and each plant has a head of small yellow flowers that produce dozens of seeds that can be blown about by wind and often grow in pasture land and ditches. If left uncontrolled spurge and the other noxious weeds can choke out other grasses and plants that wildlife and livestock feed on.

“Leafy spurge generally grows in patches and they’re pretty manageable,” Novak said. “Maybe after many, many years it’s a possibility that they could overtake a (pasture), but it’s not like within a year or two or anything like that.”

Novak said a common way for leafy spurge to spread is by the transportation of hay, especially hay that has been cut in ditches. Landowners are required to control noxious weeds by state law.

“With leafy spurge there’s actually a biological control called the leafy spurge beetle, and that beetle will feed on spurge, so that is a recommendation if you don’t want to use chemicals,” Novak said.

Holding ground

While noxious weeds pose a minimal threat, other invaders pose a menace to rivers and lakes in North Dakota. Zebra mussels feed by filtering plankton from lake waters, which not only reduces food supplies for native species but improves water clarity which can lead to more vegetation growing on the lakes’ beds. Increased vegetation can affect oxygen levels as the plants die and decay over the winter, which in turn can lead to large populations of fish suffocating to death.

Zebra mussels can attach themselves to boats and hitch rides from lake to lake. The North Dakota Game and Fish Department’s Aquatic Nuisance Species Division lists zebra mussels as a species that was previously documented to be present in North Dakota but are not known to be currently present. However, Minnesota has several lakes that have been infested. Pipestem Dam Manager Bob Martin said the NDGF monitors the Jamestown Reservoir for the mussels by setting traps out in the spring.

“They’re (the traps) like PVC pipes that they attach to one of the boat docks that’s out in the water,” Martin said. “They put them in at the beginning of the season and at the end of the season they see if anything’s attached.”

Checking boats as they are removed from lakes is vital to stop the spread of zebra mussels. State law requires all water to be drained from a boat before it can be transported and all aquatic vegetation must be removed as well. Aquatic Nuisance Species Coordinator Fred Ryckman said in an NDGF news release that there are more than 400 recreational fishing waters in the state, making it imperative for these regulations to be followed.

“It is the same message year after year, but that just shows how important it is to keep our waterways free of unwanted species,” Ryckman said in the release. “Full public participation and compliance is critical if we want to ensure ANS is not transferred from one lake to another.”

Downstream from Jamestown near Aberdeen, South Dakota, officials are worried about a possible rise in the invasive carp population. Last year the Aberdeen News reported invasive carp —formerly called Asian carp — had begun trying to jump over the water control structure on the Sand Lake National Wildlife Refuge, with several of them found dead and rotting atop the structure. In 2011 the carp were discovered in the James River after swimming north through flood waters in the river to the Jamestown Dam.

“They (NDGF) come over here and search for those carp below the Pipestem and Jamestown dams,” Martin said. “After they were discovered they do even more.”

At our doorsteps

While efforts to keep zebra mussels and invasive carp out of North Dakota have been successful so far, another invader from Minnesota is threatening the state.

The emerald ash borer lays its eggs in the fissures of ash tree bark, and when they hatch the larvae burrow into the tree and leave tunnels up and down the wood of the tree as they feed on the inner bark. Doing so negatively affects how a tree distributes water and nutrients throughout its system. They eventually burrow out of the tree leaving a D-shaped hole behind them. Trees will eventually begin dying from the top down and by the time the holes are discovered it may already be too late. The city of Jamestown website says there are several insecticides being tested and sold as a short-term cure, but the chemical effects on the trees and their success rates both vary. Some leading manufacturers like Ortho and Bayer also sell preventative treatments for trees as well.

A common method of transportation for the borer is in campfire wood being transported to and from various campgrounds. Most campgrounds in the state have regulations posted about not transporting non-local firewood.

Jamestown City Forester Doug Wiles could not be reached to comment for this article, but at a previous meeting of the Jamestown Parks and Recreation Commission earlier this spring he said it’s estimated 90 percent of the city’s ash trees will eventually be infested by the borer.

“Right now our ash tree inventory is over 40 percent of our boulevards, so that’s a ton of ash trees,” Wiles said at the meeting. “Ninety percent of that and our streets will be even more bare.”

Sun reporter David Luessen can be reached at 701-952-8455 or by email at dluessen@jamestownsun.com

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