Moffat County officials want residents to watch out for yellow start thistle, a noxious weed that can potentially cause the death of any horse that eats it.

Gary Brannan, Moffat County pest manager, said local crews first found the weed last year near Maybell. It has not seemed to spread across the county, but he wants to make sure the plant remains under control.

Unchecked yellow star thistle populations can easily take over an area and force out all other vegetation, Brannan said.

"Each one can produce thousands of seeds," he said. "I would really like the public's help with this. If they see them, please report them."

Yellow star thistle, which is easily spotted by its bright yellow flower and 1- to 1.5-inch spines on its stalk, has taken over about 10 million acres in California, Brannan said. That area is equal to about three times the size of Moffat County.

Yellow star thistle is poisonous to animals but particularly harmful to horses because it causes them to develop a mouth disorder, he added.

"They get to where they can no longer chew or swallow, and they either die of dehydration or starvation," Brannan said.

Officials suspect the flower came to Colorado along with energy industry traffic.

The county recently received a state grant to hire a two-man crew that will spray areas where the weed is found, Brannan said. The grant will pay 85 percent of the cost, and the remainder will come out of pest management reserves.

To report the weed, residents should call the Colorado State University Cooperative Extension Office at 824-9180, and crews will come out to take care of the problem for free.