Crop & Pest Report


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Waterhemlock Reported in Cass County (07/30/20)

A suspicious weed in the parsley family was reported to the Cass County Extension office within the last two weeks.

A suspicious weed in the parsley family was reported to the Cass County Extension office within the last two weeks. Both the Cass County Extension Agent and Weed Control Officer visited the fields in the South-Central part of the county to collect plants for identification. These plants turned out to be waterhemlock (Cicuta maculata), which is one of the most acutely poisonous plants we have in North Dakota. The infestation is currently known on about 15 acres of grass hayland and adjacent roadside ditches and water drains. It is probable that these plants were established several years ago and have since spread. Waterhemlock spreads by seed and thrives in moist soils, so floodwaters are of great concern in aiding the spread of waterhemlock.

Waterhemlock is a perennial weed in the parsley family. It can be easily confused with other plants in this family due to the flowering structures. Waterhemlock has clusters of white flowers arranged in an umbel, similar to other weeds like wild carrot or poison-hemlock. The leaves of waterhemlock can help differentiate it from similar species. Waterhemlock leaves are narrow-toothed, 1-4 inches long, and divided 1-3 times. The leaflet veins run from the midrib to the notches on the leaf margins. Another identifying characteristic is a hollow stem that often contains hollow, horizontal chambers that can be observed by splitting the root base of the plant. Use caution when splitting a root, as this is the most toxic part of the plant and can cause skin rashes on some individuals.

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Waterhemlock is a weed of great concern to livestock producers due to its toxicity when ingested. Typically, ingestion will take place when waterhemlock is mixed in with hay bales. Any potential plants should be mowed around to avoid baling, and care should be taken to avoid feeding at all costs. Other states have reported that chemical control is best achieved with high rates of glyphosate, 2,4-D, or MCPA at the bud-to-early-bloom stage. The infestations that were walked are all past that growth stage, so the level of control using these products is not known, but will likely be less than earlier applications. If plants are in or near water, then formulations that are safe to apply in aquatic settings should be used. Livestock producers should be on the lookout for this weed and long-term management will be needed to control these infestations and prevent accidental ingestion by livestock.


Joe Ikley

Extension Weed Specialist

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