By Blake Jackson
Poison hemlock, a toxic weed, is emerging in Missouri pastures, posing a threat to livestock, according to Kevin Bradley, University of Missouri Extension weed scientist. It can cause death and birth defects, particularly when consumed during early pregnancy.
This plant thrives in ditches, roadways, fencerows, shaded pastures, and no-till fields. In its first year, it develops a flower stalk, and in its second, it bolts to heights of up to 10 feet.
It's often mistaken for wild carrot, or Queen Anne's lace, due to their similar umbrella-shaped white flowers. However, poison hemlock has a hairless, purple-mottled stem, while Queen Anne's lace rarely exceeds 2 feet and is harmless.
Control poison hemlock early, during the rosette stage, using pasture herbicides before flowering. Mature plants are less responsive to chemical treatments. Non-chemical options include hand weeding, mowing, and tillage.
Pasture herbicides containing 2,4-D, dicamba, or 2,4-D plus triclopyr are effective. Dicamba plus glyphosate offers consistent control, but glyphosate should be used cautiously to avoid damaging desirable forages.
All parts of poison hemlock contain toxic compounds that affect the nervous system, causing tremors, paralysis, and potentially death within hours of ingestion. Cattle are most susceptible to birth defects, but other livestock are also at risk.
Tim Evans, MU Extension veterinary toxicologist warns that cows consuming poison hemlock in their first trimester may give birth to calves with skeletal deformities, known as crooked calf syndrome. Pigs, sheep, and goats can exhibit similar deformities.
Immature leaves are most palatable to livestock, but mature plants are usually avoided. However, poison hemlock incorporated into hay poses a risk. Historically, poison hemlock was used in executions, such as that of Socrates.
Its toxins can also irritate skin, so protective gear, including gloves and eye protection, is essential when handling the plant. Early detection and control are crucial for protecting livestock and preventing the spread of this dangerous weed.
Photo Credit: gettyimages-jacqueline-nix
Categories: Missouri, Livestock, Beef Cattle, Dairy Cattle