Quck answer
Bitterweed is a common weed found in pastures and can be harmful to livestock if ingested. To effectively kill bitterweed in a pasture, follow these steps:
1. Identify the bitterweed plants by their yellow flowers and fern-like leaves.
2. Use a selective herbicide specifically designed to kill broadleaf weeds without harming grass.
3. Apply the herbicide during the weed’s active growth period, typically in the spring or early summer.
4. Follow the herbicide’s instructions for mixing and application rates.
5. Spot treat the bitterweed plants, spraying directly onto the foliage.
6. Repeat the application if necessary, as some plants may require multiple treatments.
7. Regularly monitor the pasture for new bitterweed growth and treat accordingly.
By following these steps, you can effectively eliminate bitterweed from your pasture and prevent harm to your livestock.
The sight of bitterweed (Hymenoxys odorata) — yellow flowers sprouting in the pastures and rangeland of the Southwest — may cause farmers and ranchers to feel disappointed. This yellow-flowered plant, a member of the aster family (Asteraceae), is toxic when consumed by sheep, cows, and other livestock.
What Is Bitterweed?
If bitterweed is present in your area, it is important to identify it before it harms your livestock. The easiest way to control bitterweed is to get rid of it before it becomes a problem. Bitterweed is an annual plant with straight stems that can grow up to 2 feet tall. It produces yellow flowers that surround a yellow seed head. Bitterweed spreads because the wind carries its seeds and disperses them.
Bitterweed grows across a large area in the Southwest, mostly from southern Kansas to Mexico and from central Texas to California. Livestock often attempt to graze on bitterweed during winter and early spring when other foliage is dormant. Bitterweed thrives in spring and early summer, but it can produce seedlings at any time of the year depending on rainfall and temperature.
Bitterweed has a close relative called pingue (Hymenoxys richardsonii), which is a perennial plant that resembles bitterweed and has a similar toxic effect on livestock. Like bitterweed, livestock will not consume pingue if grass and other forage options are available. Another type of bitterweed, Helenium amarum, grows in southeastern and south central states and is toxic to livestock when consumed in large quantities.
Controlling Bitterweed in Pastures
If you have bitterweed growing in your pasture, it is crucial to eliminate it because it is particularly toxic to sheep. Sheep are more likely than other livestock to consume bitterweed. The name bitterweed comes from the sour milk produced by animals that eat the plant.
Bitterweed not only makes milk taste sour, but it also has a bitter taste for most livestock. Unless there is no other forage available, livestock will generally avoid consuming bitterweed. One method of controlling the growth of bitterweed without using pesticides is to mow it and plant robust perennial grasses, which will outcompete the bitterweed. Another approach is to rotate livestock through different pastures.
Bitterweed can be controlled with pesticides applied from fall to early spring, but ensure that livestock are not grazing in the pasture. Use 2,4-D, picloram, clopyralid, or metsulfuron no later than early spring, before the plant starts to flower. It is important to follow the instructions on the label when applying the herbicide and to adhere to any precautions, especially the recommended time frame before reintroducing livestock to the pasture.
Signs of Bitterweed Poisoning
If you have livestock, particularly sheep, that have consumed bitterweed, remove them from the pasture containing bitterweed and provide them with water containing electrolytes. Feeding methionine and soybean meal may also be helpful. If there is a possibility that livestock may consume bitterweed, feeding onions high in cysteine may help prevent the negative effects of bitterweed.
Sheep that have consumed bitterweed may appear depressed and may grind their teeth. They often hunch up in an attempt to alleviate stomach pain. Bits of vomit may be visible around their nose and lips. Cattle will exhibit similar effects if they have consumed large quantities of bitterweed.
If animals are taken away from bitterweed as soon as they show signs of poisoning and are placed on pastures with healthy grass, they usually recover. The symptoms of grazing on bitterweed typically appear within two to four weeks. There is no known cure, and if livestock remain on a pasture with bitterweed, they are unlikely to survive.
