- An Exciting New Product for the War on Star Thistle
We all know how
miserable star thistle is; painful to walk through, dangerous for eyes, and potentially
deadly to the horse if much of it is consumed. Ingestion of the weed over a period of time
leads to neurological damage manifested as difficulty in swallowing. An afflicted horse is
unable to eat or drink, and the condition is not reversible.
Mowing, burning, older herbicides and pulling by hand have all been used to manage star
thistle, but with limited results. The seeds live for many years in the soil and even with
regular efforts at control will continue to reinfest pastures. To have effective long-term
control, the seeds in the soil must be depleted, and new seed production must be halted
for at least three years.
Now, a recently licensed herbicide
called Transline® gives us a very effective
tool in battling this dangerous pest. Like any chemical herbicide it needs to be used as
part of a well-planned, holistic strategy. Transline®
has achieved a very high kill rate on star thistle in trials done by Dr. Joe DiTomaso at
the University of California at Davis. He writes, A limited number of herbicides are
registered for use in California rangelands and pastures. Of these, the majority are
applied to the foliage of target plants, including yellow star thistle. Most of these
compounds, including 2,4-D, triclopyr (Garlon), dicamba(Banvel), and glyphosate (Roundup)
have little or no soil activity, and thus will not control seedlings emerging after
herbicide application. In contrast, the newly registered herbicide clopyralid (Transline®),
has excellent soil (preemergence) and foliar (postemergence) activity. Most legumes,
such as clovers, will be killed by the Transline®,
but other grasses will not be. If desired, the clover can be re-seeded after the use of
the Transline®. It is not necessary to keep
horses off the pasture after it is sprayed, but may be wise to keep them well fed with hay
for several days after spraying to minimize their intake of the sprayed foliage.
The best results have been obtained with application of Transline®
between January and March, so that the new seedlings are killed and the product remains
active against seeds that continue to sprout. It only needs to be applied once per year,
and for three years for best control. The product is sold only in large containers, and is
quite expensive per gallon. Only a small amount is used per acre. A site
number must be granted by each countys Agriculture Commissioner for
record-keeping, and specialized equipment is necessary for application. For most horse
owners hiring a contractor to do the work is the way to go. There is a minimum charge for
application, but the cost per acre is quite reasonable.
The Agriculture Commissioners office for your county can give you a list of licensed
pesticide control applicators. The UC Davis Cooperative Extension office in each county
may also be able to help. Edson Enterprises is based in Sonoma County, and is available to
apply Transline® in other counties as well.
They can be reached at (707) 838-3899. They will give a free estimate, and handle all of
the necessary paper work.
Stephanie Larson, UC Davis Cooperative Extension Range Management Specialist for Sonoma
County, emphasizes the importance of good planning and follow-up in achieving good
control. Seeding with plants that compete w/ the star thistle, fertilizing,
spot-spraying, and the use of biological controls will all help after the initial
knockdown is achieved with the Transline®.
Her office is available for advice to people from all counties; the phone number is (707)
It is important to make plans early if you wish to use Transline®.
There are not many commercial applicators doing the work yet, and they will have a lot to
do to get the Transline® applied during the