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Yellow Starthistle Mapping Project: Cooperative Survey 2000

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Cooperative Survey 2000

The Sierra Nevada Cooperative Yellow Starthistle Mapping and Assessment Project (YSTMAP) wrapped up its second season this fall. In 1999, CDFA and the California State Department of Transportation had coordinated efforts to map occurrences of yellow starthistle (YST) on the highway system in the Sierra Nevada. This year, inventory efforts by many agencies were brought together to create a picture of the extent of YST in the Sierra Nevada. The ability of Weed Management Areas to bring together the agencies that gathered the data for this project made this project possible.

I. Goals

  1. Determine the eastern edge of YST in the Sierra Nevada;
  2. Determine the area in the Sierra Nevada where YST is limited to outlier infestations; and
  3. Determine a containment area in the Sierra Nevada where YST could reasonably be eradicated.

 

The idea behind the project is to use the mapping data to focus control work on YST where it is relatively rare, and to keep it from becoming well established.

II. Results

The mapping that was done this year does show the extent of YST in the Sierra Nevada (see map). Along some of the Highways like 80, 50, and 88, YST is seen very far east and as high as 8,000 feet. In the southern part of the range, YST
rarely is seen above 2,000 feet. Many smaller, isolated infestations of YST (outliers), have been identified. As the Weed Management Areas in the Sierra Nevada prioritize the control work that they will spend AB 1740 funds on, they should use this data to define a containment area to determine where to start work on yellow starthistle. Some of the locations that were included in the data this year were also treated this year, so work towards control of YST in the area is already underway.

The mapping and assessment of YST in the Sierra Nevada is really more of a process than a product. The current mapping of YST does not contain every
location that YST existed in the Sierra Nevada. For example, relatively little work
was done on private land. As time goes on, work that Weed Management Areas do with private landowners will expand the scope of the inventory. Also, some of the inventory data is not really adequate to inform on-the-ground decision making, because it doesn’t include the size of the infestations. Without that data, you can’t assess the cost of control, or whether the infestation would be easy to control manually. Future inventory work should be refined to include that information.

From here, the Weed Management Areas can continue to maintain and refine the inventory of YST, and use the model of centralizing weed inventories in an area to prioritize control work on other weed species, as well as continuing to stop the spread of yellow starthistle.