If you look at the green area-- that's the 'flatweed' one is a dandelion and the other is a catsear.
The dandelion is a familiar perennial weed whose leaves grow flat on the ground atop a long perennial taproot.
I found this on another forum about Australian stringhalt..
Australian Stringhalt, aka dandelion poisoning is bloody awful! I have seen at least half a dozen horses with it, to varying degrees, and it depends on how early it is caught as to recovery time. I have seen a mare that was still not right 14 months out from it being diagnosed (she was not noticed until she could barely stand or move!), and horses that were fine after a month or so.
It's not just Catsear, but also true dandelion that are the problem, and it's worst in drought, possibly because little other vegetation survives, and the horses then eat more or the dandlion, which survives drought quite well. As soon as you see any sign of the problem it is essential to get the horse off the pasture, and somewhere they can't get at the dandelion. Whatever the toxin is, it causes nerve lesions, and the longer the exposure is, the worse the damage.
Australian Stringhalt The dramatic hind leg flexing is the same, but the cause of the nerve damage in Australian stringhalt is different from the classic condition. Horses grazing drought-stressed pastures in Australia and New Zealand may consume one of several plants including flatweed (cat's ear), fireweed, mustard weed (skeleton weed), and dandelion. Nerve damage and muscle wasting have been linked to ingestion of a mycotoxin in these weeds, which may constitute a large percentage of pasture herbage after grasses have wilted in dry months. Australian stringhalt may affect any breed, although draft horses and Thoroughbreds account for the largest number of cases.
In addition to nerves in the hind leg, long nerves elsewhere in the body, especially those controlling the larynx, are commonly affected by the toxins. Some degree of laryngeal paralysis is common in horses with Australian stringhalt, resulting in horses that "roar." Phenytoin, dilantin, baclofen, and vitamins B and E have been used to reduce signs of the condition, and results have varied. Horses removed from contaminated pastures usually recover, although progress may be slow, taking up to 18 months before normal motion is restored.
Rutgers Equine Science Center in New Brunswick, NJ announced that a toxic plant called “Catsear” has been found growing in areas as far north as New Jersey due to the high amount of rain and moisture. Horse owners should be aware of this plant as it is easily confused with the common dandelion. Dandelions are not poisonous to horses, but Catsear has the potential to be dangerous if consumed in large quantities, and Rutgers notes that some horses have been eating the plant even if adequate forage is available.
View slideshow: Catsear has been found in New Jersey pastures. The plant is poisonous to horses if ingested in large quantities. Horses have been found eating the plant according to Rutgers University.
Catsear is suspected to cause stringhalt which is a neurologic problem where the horse exaggerates the flexing of its hind legs when walking. The condition caused by the Catsear plant is known as Australian stringhalt due to its prevalence in Australia and New Zealand. Stringhalt is commonly associated with vetch and sweet pea poisoning in horses.
Toxic Catsear has been identified in horse pastures as far north as New Jersey by Rutgers University. Rainy weather is responsible for the abundance of this plant toxic to horses.
Photography by Marcya Roberts, freelance writer for Examiner.com
Keep an eye on your pastures for Catsear and other toxic plants and remove them as necessary to ensure your grazing areas are safe for horses. How to identify Catsear
At first glance, Catsear plants look very similar to Dandelions, but the two plants differ in stem and leaf structure. The photo that accompanies this article was identified as Common Catsear (also known as False Dandelion) by Dr. Bradley A. Majek of Rutgers University Department of Plant Biology and Pathology.
Rutgers provides some details on how to tell Catsear apart from Dandelion:
Stems: Catsear has several stems with multiple flowers per plant, while Dandelions bear a single flower per plant.
Leaves: Catsear has soft, hairy, rounded/curved-lobed, and darker green leaves compared to Dandelion with its hairless, lighter green, course/pointed, deeply serrated leaves.
Flower: Underneath the flower, the green leaf-like structures (sepals) cling to the yellow catsear flower. In Dandelions, the sepals curl away from the flower.
Season: While Dandelion blossoms in the early spring, Catsear blossoms in the early summer.
The winters here were very long and every dandelion I've dug up out of our garden this year have smelled like mold- had been half eaten by rolly pollies- or had visual white mold and dust on them. I can provide pictures of them being half rotted in the ground and the flower still being bright yellow-- that's when theyre the most dangerous-- the ground is moist and where there is moisture there is mold-- mycotoxins are black mold that are 'invisible' to the naked eye.
The dandelion itself isnt the dangerous thing. Its the mycotoxins that grown on these plants with flat weeds that cause australian stringhalt.. if you read the link I provided above.
Dandelions grow when the ground isnt at its best and I would be more worried about it now with the very harsh winter weve had- if you don't believe me. Ill make sure to pull some up out of my garden and flower beds and show you what the roots look like if ya wish?
I know some people might eat dandelions and that's fine-- if its in a garden type setting and is properly taken care of- like any greens from the garden. Dandelions growing in rough warn down pastures-- growing because there is no other nutrients for good healthy grasses to grow.
Like I've said-- its the mycotoxins that contaminate the plant-- catsear alone don't cause australian stringhalt- the mycotoxins do.. symptoms of poisoning from a toxic plant and australian stringhalt are not even the same at all. In order for your horse to even want to eat toxic plants they are either overly thirsty or under fed.. (not saying that's the case here- please don't take offense ) and in order for a horse to be poisoned by catsear theyd have to eat a lot of the plant.. 1 aint going to kill your horse..
Once again- that's false information-- mycotoxins cause australian stringhalt.. not the catsear plant alone.
The most common plant species that have been found and identified in pastures where affected horses were located include: Flatweed (Hypochaeris radicata), Sheep Sorrel and Couch. The type of nerve damage sustained in horses with Australian Stringhalt suggests a mould toxin (‘mycotoxin’) or a fungal ‘poison’ found in the soils may be a cause for this condition. Mycotoxins can directly affect the long myelinated nerves in the hind limbs.