Monday, October 18, 2010

Yellow Starthistle: Noxious Weed

Yellow Starthistle (Centaurea solstitialis L.)

"Noxious weed: any living stage (including seeds and reproductive parts) of a parasitic or other plant of a kind which is of foreign origin, is new to or not widely prevalent in the U.S., and can directly or indirectly injure crops, other useful plants, livestock, poultry or other interests of agriculture, including irrigation, navigation, fish and wildlife resources, or the public health." ~Federal Noxious Weed Act 1974
One of the noxious weeds that I see everyday when I walk my child to school is the Yellow Starthistle.  The flowers may look innocent but the Yellow Starthisle is registered in the list of noxious weeds in California.  Its aggressive spread affects the yield and quality of rangelands, pastures and grasslands.  The spines on the flowers make it less palatable to livestock; hence they avoid areas that are infested with the weed.  In this case the spread of Yellow Starthistle does not affect livestock per se but it reduces the effective grazing area. 

For the horses, however, this weed is food.  Horses eat this weed and they are capable of chewing and digesting it.  When a horse consumes a certain amount of this toxic weed, it can contract a neurological disorder called "chewing diseases" (Nigropallidal encephalomalacia).  Inability to swallow and chewing in the absence of food in the mouth are among the symptoms of the disease.

This weed is wanted in California!  You and I are licensed to kill it.  If you are looking for an opportunity to have no mercy on a plant - this is it!

Read more about this weed:


Curbstone Valley Farm said...

We saw so much of this when we lived in the Central Valley. I've slaughtered more than my fair share of this weed. Fortunately, once removed, if the area is replanted, it doesn't compete well with other other plants, so unlike some invasives, it is a little easier to control, with some effort up front.

For horses on pasture, the key, other than removing it, is to ensure there is plenty of alternative forage, especially in late summer. Horses most at risk for developing neurological disease, are those restricted to primarily star thistle in their diet over an extended period of time. In the presence of quality forage, thankfully, most horses preferentially avoid it.

Helen Lewis said...

Thanks for adding such useful information to this post! I agree with you completely! We have so many of them around here that I have to do my part to campaign for their extermination!

fer said...

Interesting to see this is a pest, I have seen it many times but i never knew it was bad. Good to know to be on the lookout

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