Noxious weeds are a farmer’s nemesis, easily spread by unknowing gardeners and landowners, and potentially devastating to other plants. North Dakota plant businesses and state agencies are using education as a tool to help prevent these invasive plants from getting a greater foothold.

Public Plant Enemies

More than nuisances, “noxious weeds are plants most likely to spread and cause economic damage, health concerns, and habitat degradation,” says Rod Lym, North Dakota State University (NDSU) weed scientist. The state maintains a list of 11 noxious weeds, with additional species added by some counties and cities.

It is especially important to raise awareness about noxious weeds with attractive foliage or flowers, like purple loosestrife, that are visually appealing but environmentally devastating.

“It overtakes the native vegetation, and a lot of the wildlife that live along creeks and the banks of streams and rivers lose their food source,” Lym says. Tiny purple loosestrife seeds – up to 2.7 million per plant – are easily spread by wind and water.

NDSU and the North Dakota Department of Agriculture (NDDA) distribute educational materials at garden shows and other events to help homeowners identify and control invasive weeds.

“Proper plant identification is the first step in weed control,” says Chelsey Penuel, NDDA noxious weeds specialist.

Spotted Knapweed

Spotted Knapweed

Protecting the Farm

Farmers and crop consultants also learn about invasive weed control from NDDA and NDSU publications, educational seminars, and field days. Producers can also be confident they are not unknowingly sowing contaminated seed, by purchasing seed inspected and certified by the North Dakota State Seed Department (NDSSD).

“While certification standards permit a minimal number of common weed seeds in a sample, there is no tolerance for the presence of prohibited noxious weed seed,” says Steve Sebesta, the seed department’s deputy commissioner.

State agencies also work to keep potentially devastating weeds from even entering North Dakota. One current concern is Palmer amaranth, a tiny-seeded weed not confirmed in the state at the start of 2017.

“Palmer amaranth spreads so fast, is very difficult to control and has become resistant to many of the herbicides,” Lym says.

The NDDA, NDSU and the state seed department have coordinated extensive preventative measures to keep Palmer amaranth at bay. The state seed department, whose inspectors are in fields all season, is an important first line of defense.

Thistle White Flowers

Thistle White Flowers

Homeowners and Horticulture

North Dakotans may rely on numerous strategies to avoid unintentionally spreading contaminated seeds for home landscapes, pollinator gardens and wildlife habitats. “Home gardeners and landowners should always purchase seeds from reputable sources,” says Esther McGinnis, NDSU horticulture specialist.

Buying properly identified plants, instead of planting from seed, is a recommended weed control approach.

“Planting plugs, instead of sowing from seed, is now standard practice in the state’s 18 Master Gardener pollinator gardens,” McGinnis says.

Excavation for new homes can stir up dormant weed seeds and create more favorable germination conditions.

“We recommend applying an appropriate rate of glyphosate herbicide to eradicate weeds, before laying sod or seeding grass. Always use chemicals approved for residential use,” McGinnis says.

Leafy Spurge

Leafy Spurge

Leafy Spurge Biocontrol

Biocontrol is another successful prevention strategy.

“Biocontrol involves going back to the native habitat of the plant and screening for pathogens or insects that could control the weed here,” Lym explains.

These efforts have proven effective in the past, particularly in controlling leafy spurge, an invasive weed with root systems that can reach up to 30 feet deep.

“We gained approval to release some insects in the late 1980s,” Lym explains. “We monitored those insects in areas called insectaries, redistributing the insects as populations grew.”

The most impactful insect was a type of flea beetle, first released in the early 1990s. “Adult insects feed on leafy spurge leaves. However, it is the larvae that cause the most damage when feeding on the plant roots,” Penuel says.

The proliferation of the flea beetle is credited with helping cut the area infested with leafy spurge in half, and that area continues decreasing.

“We’re never going to eradicate a weed like leafy spurge, but we can control it,” Penuel says. “The goal of biocontrol is to create a balance.”