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Grass
Valley (Note: no pictures available prior to spraying.)
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6/7/99
Rosettes of Musk Thistle killed by Rodeo herbicide. Sprayed 5/18/99.
Shows typical effectiveness of this herbicide. Note red pencil for
scale.
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9/15/99
Large rosette of Musk Thistle which sprouted after the area was
treated. Many new rosettes sprouted after the area was sprayed.
Note red pencil for scale.
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5/11/01
Sagebrush
seedlings and many new Thistle rosettes. Note red pencil for
scale.
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1. Treatment. |
At
this location Musk Thistle was sprayed with Rodeo herbicide. Treatment was
in the spring (May or June) during 1999 and 2000; application rate was 1%
solution of herbicide with a surfactant added. Individual plants or clumps
of plants were spot sprayed. There was no broadcast application.
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2. Results. |
| Rodeo
herbicide killed the Musk Thistle plants that were sprayed. The soil here,
however, contains a great amount of seed and is annually reseeded by thistles
from the surrounding meadow. Each summer after the spraying treatment a
new crop of thistles appeared as rosettes, which matured and were sprayed
the following year. After two years of treatment there appeared to be an
increase in iris and sagebrush seedlings, apparently released from competition
by the thistles. |
3. Conclusion. |
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Persistence is the key to controlling
an established stand of Musk Thistle. Rodeo herbicide is effective on live
plants but cannot control the germination of seed in the ground. Two applications
each year, in spring and again during summer or fall, would allow a quicker
control by killing the seedlings (rosettes), which appear after the spring
spraying. |
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