Yellow Starthistle Toxicity
Yellow starthistle is an invasive weed that is more than just a pesky plant. It is a fast growing and widely spread specimen that takes over grazing land and may harm in more ways than one. It is a flowery, thorny weed that can injure and is potentially deadly. Does this Spark an idea?
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Origin of Yellow Starthistle
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Yellow starthistle (Centaurea solstitialis) is related to the sunflower and originated in the Mediterranean. It may have entered the United States through contaminated seed shipments that arrived in California. Through animal consumption and other natural mediums such as wind and rain, the seeds were carried throughout the United States. Yellow starthistle is in almost every state, with the highest concentrations found in California and Oregon.
Identification
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Yellow starthistle is a tall flowering plant that can grow up to 30 inches in height. The stem is covered in thin translucent hairs and is topped with a bright yellow flower that is similar in nature to a dandelion. At the base of the bloom are a number of long, thin thorns approximately 3/4 of an inch in length. The thorns grow in a star-like pattern around the stem, thus the name yellow starthistle.
Yellow starthistle is an annual, blooming in the months of July and August. As autumn approaches, the yellow blooms dry, and much like the dandelion, turn into wispy balls of feathery plumes. These plumes contain some of the seeds of the plant and are carried with the wind to seed elsewhere.
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Toxicity
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Yellow starthistle poses a couple of different dangers to grazing animals. Yellow starthistle is an extremely spiny plant and the thorns are a danger to all animals that come in contact with it, as they can pierce skin, eyes and mouths.
Consumption of the plant can have extreme consequences. Some cattle and horses find yellow starthistle tasty and prefer it to regular feed. Animals with the taste preference tend to consume large quantities of the plant, which can result in poor nutrition for cattle and poisoning in horses.
Horses are the only known animals to experience toxicity from yellow starthistle.
Symptoms
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Consumption of large quantities of yellow starthistle (anywhere from 86 to 200 percent of the animal's body weight) over a period of one to two months can result in Equine nigropallidal encephalomalacia, commonly called "chewing disease."
The toxin that is produced during digestion causes irreversible brain damage in horses. Early signs of toxicity may be difficulty in walking or standing, lack of muscle movement in the face, and even Parkinson's-like ticking or trembling in the legs. Advanced symptoms of the disease are an inability to eat or drink as the toxin destroys the area of the brain that controls these functions.
There is no cure for the disease, and eventually the affected animal will die of either thirst or starvation.
Prevention/Solution
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The only prevention is the extermination of the weed. It is a resilient plant, and requires a multi-layered approach to control or eliminate it.
Weed control matting is recommended as a preventative to unaffected areas. Additionally, if one has walked in an area that contains yellow starthistle, removing residue from shoes and pants can help prevent the spread of seeds to thistle-free zones.
Introduction of weevils and flies into the yellow starthistle environment can deter seed production as the insects feed on the plant heads and seeds, cutting down plant reproduction by almost 50 percent in some studies. Weevils such as bangasternus orientalis and flies such as Urophora sirunaseva have been used in studies with some success.
Planting of grasses in affected areas can be a successful and green approach to beating yellow starthistle infestation. The grass grows in greater density and will eventually begin to take over the area, growing over the spring buds of yellow starthistle, robbing it of the sunlight that is necessary for successful growth.
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References
Resources
- Photo Credit distel nach eiszeit image by madlen stahl from Fotolia.com
