NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

July 1, 1999

Purple Loosestrife Tour Set for July 16 in Valley City

A purple loosestrife tour will begin at 1 p.m. on Friday, July 16, at the Chautauqua Park in Valley City. Those participating in the tour will learn how to identify purple loosestrife and how to control the weed using chemical and biological control agents. The tour will also include discussion on the life cycle of the introduced biocontrol insects and how to identify them.

"The tour is being held at Valley City because this site has the most successful establishment of biological control agents introduced into North Dakota for purple loosestrife control," says Rodney Lym, invasive weed specialist at North Dakota State University.

During the tour, Jim McAllister, Barnes County weed control officer, will discuss the control efforts being conducted in the county. Also, John Leppert with the North Dakota State Department of Agriculture will discuss statewide efforts to control purple loosestrife.

Also known by its genus name, Lythrum, purple loosestrife was added to North Dakota's noxious weed list in 1996. It is the first horticultural plant to be declared noxious in the state, Lym says. A beautiful garden plant with an aggressive nature, purple loosestrife was first introduced into North America in the early 1800s, and it has been sold in North Dakota by its genus name for at least 50 years.

Lythrum plants were brought to North Dakota for flower gardens because of their striking color, ease of growth, winter hardiness, and lack of insect or disease problems. Lym says the garden varieties of purple loosestrife were sold by many cultivar names including Morden Pink, Dropmore Purple and Morden Gleam.

"These garden cultivars were thought to be sterile but have now been shown to cross-pollinate with the wild Lythrum type and sometimes with other Lythrum cultivars," Lym says.

The major impact of purple loosestrife invasions is on the ecology of aquatic sites. Purple loosestrife forms dense stands that displace native wetland plants. Lym says that under optimum conditions, a small isolated group of purple loosestrife plants can spread to cover aquatic sites in just one growing season.

"When purple loosestrife replaces native vegetation it also can displace wildlife," Lym says. "For example, songbirds do not consume the small hard seed. Muskrats use cattails to build their homes, and they show a preference for cattail over purple loosestrife for food. Waterfowl, especially ducks, avoid wetlands that have become dominated with purple loosestrife. In addition, overall waterfowl production is decreased as suitable nesting habitat is eliminated."

Purple loosestrife has been heavily utilized in North Dakota flower gardens, park plantings and golf courses. North Dakota law allows previously established Lythrum plantings to remain if the plants do not produce seed and present no danger of spreading to aquatic sites, but if the Lythrum plantings produce seed or could spread to aquatic sites they must be eradicated, Lym says.

Aquatic sites are defined as rivers, lakes, sloughs, dams, dugouts, bogs, swamps, irrigation ditches, streams (perennial or semi-permanent) and other water courses, or wet sites. Weed boards will determine on a case-by-case basis which ornamental Lythrum plantings present a threat to aquatic sites.

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Source: Rodney Lym (701) 231-8996

Editor: Dean Hulse (701) 231-6136