Narrowleaf Hawksbeard and Marestail

Narrowleaf hawksbeard and marestail are two invasive annual weeds that resist a widely used herbicide called Glyphosate. These weeds have become increasingly problematic over the years in the Western North Dakota and Eastern Montana area.

Marestail, commonly known as horseweed, is a broadleaf weed that germinates in the fall, spring, and early summer. Marestail has become a big problem in no-till fields, reduced tillage production systems, and more recently a problem in some tilled fields. The weed does not mature until late summer, which creates competition with crops and can also cause an interference with harvest.

Marestail can grow up to six feet tall and exhibit many small flowers during the months from July to October. The small flowers produce numerous tiny seeds that disperse over long distances. The weed contains an attached pappus, which enables the seeds to travel over great lengths making the plant prevalent in several fields.

Control of marestail is known to be easy when it is in the rosette stage. This stage is when the weed begins to emerge and forms a basal rosette, this stage usually occurs in the early spring and fall. However, when marestail starts to bolt, it becomes more difficult to control. Herbicide application in the fall has shown results in decreasing the overall marestail population and the variation in plant size during the spring. Some other tips on controlling marestail are to apply herbicides when the weed is less than two inches tall, use herbicides with residual activity, and use pre-plant tillage whenever possible. "Fall control needs to become one of the tools of choice to manage winter annuals of both broadleafs and grassy weeds," explained Chet Hill, an agronomist at Hefty Seeds.

Narrowleaf Hawksbeard is a wildflower native to Eurasia. The weed resembles a dandelion, but unlike the dandelion, it can reach up to three feet tall. Narrowleaf hawksbeard has become a big problem in idled croplands seeded with grasses, no-till croplands, and hay fields. The weed is often a contaminant in alfalfa seed because it is hard to separate the two plants at harvest.

Narrowleaf Hawksbeard plants can produce anywhere from 3,000 to 50,000 seeds. The wind disperses these seeds over long distances. These plants are not a state listed noxious weed but are still very problematic to grassland areas. Producers have found that products that work well for controlling dandelions typically work well for narrowleaf hawksbeard, and that glyphosate alone is not effective. Glyphosate will temporarily stunt plants, but they continue to grow and produce many more flower stems.

At the MonDak Ag Days and Trade Show, Chet Hill will be speaking on Friday, March 2nd at 9:00 a.m. MST. He will be discussing identification and management of narrowleaf hawksbeard and marestail.

Hill grew up on a farm/ranch operation near Lambert, Montana. He has been the agronomist for Hefty Seed in Sidney for the past three years. Before, Hill was the county extension agent for eight years in Roosevelt County and was the Area Extension Specialist in Cropping Systems at the Williston Research Extension Center. Chet earned his Bachelor's and Master's degrees in Agricultural Economics from the North Dakota State University. He also has a good background in pulse crops, marketing, and general agronomy.

Hill said, " The goal of the presentation is to make growers aware of two weeds that are becoming more of a problem in our region. Identification and management will be the key to control these weeds and all weeds in general."