|Donovan, Meaghan - USDA|
|Chan, Wai - UC DAVIS|
|Greenfield, Ben - SF ESTUARY INST.|
|Shonkoff, Seth - SF ESTUARY INST.|
|Andrews, Stephen - UC BERKELEY|
Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2006
Publication Date: January 1, 2006
Citation: Spencer, D.F., Ksander, G.G., Donovan, M., Liow, P., Chan, W.K., Greenfield, B.K., Shonkoff, S., Andrews, S. 2006. Evaluation of waterhyacinth survival and growth following cutting. Journal of Aquatic Plant Management. 44:50-59. Interpretive Summary: We evaluated the potential of waterhyacinth plants to survive and regrow following treatment with three different cutting machines. We used both outdoor and field experiments. We found that 65% or greater of the plants which had all the leaves cut off survived. They began to sprout new leaves within seven to ten days after being cut. We also measured the persistence of the debris produced by the cutting machines. It remained floating in the water for longer than six weeks. In fact, it was still evident up to six months after the cutting operation. This is in contrast to the predicted rapid decomposition (less than three weeks). These results indicate that cutting waterhyacinth with the machines that we evaluated may be of limited application as a control measure in the Sacarmento / San Joaquin Delta, California where this floating aquatic plant causes significant problems.
Technical Abstract: Waterhyacinth (Eichhornia crassipes), is a serious problem in the Sacramento Delta, currently managed with herbicides and to a lesser extent biological control insects. The purpose of this study was to test the hypothesis that waterhyacinth would not survive treatments made by three types of cutting machines mounted on boats and thus result in open water areas. Waterhyacinth mats were treated by machines 1 and 2 during September, 2003 at Lambert Slough, south of Sacramento, California and at the Dow Wetlands, near Antioch, California. In June 2004, machine 3 cut plants in the Dow Wetlands. Plants collected immediately after the treatments and grown either in situ or in tubs in Davis, California began to produce new leaves within one week of treatment. Leaf production rates were higher for cut than for un-cut plants. Similarly, plant dry weight increased over the course of the experiments. All of the plants survived in the tub experiments and 65% of them survived in field enclosures for at least six weeks. At Lambert Slough, > 50% of the surface was covered by floating plant debris (2446 g dry weight m-2 and 1589 g dry weight m-2 ) after four and six weeks even though the expectation was that the material would sink and decompose within three weeks.