2011 Dry Creek Red Sesbania Monitoring Report

Sesbania_tomentosa_(5188545026)Executive Summary

The Dry Creek Red Sesbania Control Program maintenance phase, initiated in 2007, continued in 2011 with three control sweeps of the watershed in July, August and October. A monitoring visit was conducted in June before the first sweep, in September after the first sweep and in November after the last sweep was complete. The November monitoring visit indicated that less than 1% of the Sesbania population remained. Therefore, the 2011 program met its success criterion. A comparison of 2008, 2009, 2010 and 2011 monitoring results and control data is presented. Additionally, copies of powerpoint presentations given at two conferences as part of a statewide Sesbania mapping project, which included Dry Creek locations, are included, as well as an abstract for a scientific paper accepted for publication in the Journal of Environmental Management.


The 2011 treatment year was successful in removing 99% of the germinated Sesbania plants. The contractor also removed all Sesbania pods from the floodway, preventing future germination of those seeds. Since the project started in 2004 the focus has been on removal of upstream seed producing Sesbania plants, and given the reduction in seed production each year (i.e., all seed pods removed), the seedbank should continue to decline over time. While results this year are promising, treatments must continue until the population is reduced to low levels. The extent of the Dry Creek Sesbania population increased with the heavy rainfall in 2006 due to high water flows bringing seeds from low]flow channel sediments up onto the upper floodplain where they germinated far from the channel. Therefore the level of treatment effort needed in high rainfall years is expected to increase. The comparison of four years of monitoring in Table 3 shows that the number of seedlings of Sesbania germinating per meter remains high, with a slight decrease in the lower parts of the watershed. It appears from the Agri]Chemicalfs information in Table 4 that the amount of herbicide needed to treat plants is decreasing. Since the number of operator hours needed is still high, this may indicate that the number of plants sprayed is lower, because it takes the same amount of time to access the plants given the long river distances included in the treatment area.

Several presentations were made about the Dry Creek Sesbania project in 2011 and early 2012. In November 2011 the first presentation was made at the Central California Invasive Weed Symposium held in Monterey by Ramona Robison and Gary Omori. Then on January 12, 2010 Ramona Robison again presented on Dry Creek Sesbania monitoring at the state]wide California Native Plant Society Conservation Conference. Copies of the powerpoints for these presentations are included in Appendix G.

Finally, Appendix H contains an abstract prepared for a scientific paper which has been accepted with revisions for publication in the Journal of Environmental Management. The revised paper should be submitted to the Journal by May 2012 and would be anticipated to be published in late 2012 or 2013.

Contents of Report

  • Introduction
  • Methods
  • Results and Discussion
  • Conclusions

Download the 2011 Dry Creek Red Sesbania Control Program Monitoring Report [PDF*, .5 MB]

Note: Most Appendices have been omitted from the PDF version.