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Yellow starthistle: Destructive weed is encroaching on the Beehive State

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HIGHLAND — The trick is to keep as few red dots on the weed map as possible.

And it helps if the seeds don't get into streams.

Why? To keep a noxious weed that has taken over 8 million acres in California from doing the same in Utah.

"In California, it will completely cover a foothill. There are whole areas that it has made unusable, it's so infested," said Susan Garvin, a member of the Utah Native Plant Society and a forest service employee. "I would just hate to see it get that bad (in Utah)."

Garvin is talking about yellow starthistle, a bushy annual with yellow flowers and wicked spines that grows between two and three feet tall along roadsides and in pastureland. The plant is native to Mediterranean Europe and is now widespread in California, Idaho and Washington. It currently threatens rangeland and forests and can be harmful to horses if eaten.

Utah infestations have been identified from north Cache County to central Utah County and in the St. George area, Garvin said.

"Right now, we have more of this in Highland than anywhere else," Garvin said, pulling at dry plants growing near a stream in the Dry Creek area in Highland. "But we also have some around the Adventure and Learning Park (now Highland Glen Park) and patches in both Battlecreek and Grovecreek canyons in Pleasant Grove."

There have been starthistles reported in Cedar Hills and in Lindon as well.

On the weed map kept by Utah County's weed commissioner, Craig Searle, there are about 20 colored dots representing thistle stands in Utah County.

"We don't want any more," Garvin said. "The only way to stop it is now, while it's relatively new."

To combat the weeds, Garvin has sent information to all of the north Utah County cities and is organizing "pull parties" of volunteers to clear out various patches.

Garvin has sprayed where she can and is most successful with a chemical herbicide known as 2,4-D, but she can't spray on private property without permission.

She's keeping a close eye on the thistles growing near water because if left unchecked, the seeds will wash downstream and grow in new areas.

"These are starting to go to seed," she said. "That's bad for me because these are annuals that have a 5 percent seed back. That means they can start up again for up to 10 years."

Garvin hopes to raise such a clamor about the weeds that property owners and communities take notice and either pull or spray the weeds.

Garvin said Searle has purchased and released five species of biological control beetles and flies that chew into the seed heads and kill the thistles, but it's too soon to tell if that will be sufficiently effective.

In the meantime, Garvin is asking residents and visitors to call her at 801-377-5717 if any of the yellow starthistle plants are sighted.

Or people may e-mail Garvin at Sgarvin@fs.fed.us.

E-MAIL: haddoc@desnews.com