Evaluation of waterhyacinth survival and growth in the Sacramento Delta, California, following cutting

• Published in: Journal of aquatic plant management 2006, Vol.44 (1), p.50-60
• Main Authors: Spencer, D.F, Ksander, G.G, Donovan, M.J, Liow, P.S, Chan, W.K, Greenfield, B.K, Shonkoff, S.B, Andrews, S.P
• Format: Article
• Language: English
• Subjects: aquatic weeds; Brackish; Eichhornia crassipes; Freshwater; mechanical weed control; noxious weeds; plant damage; wetland plants
• ISSN: 0146-6623

Waterhyacinth (Eichhornia crassipes (Mart.) Solms), is a serious problem in the Sacramento Delta, currently managed with herbicides and to a lesser extent biological control insects. The search for alternative methods continues. 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. Machine 1 sheared off the leaves resulting in many plant fragments and plants that consisted of floating stem bases with intact root systems. The cutting motions of machines 2 and 3 differed and these machines produced numerous plant fragments along with ramets that had been split along a vertical axis into nearly intact ramets with broken leaves. 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. Cutting waterhyacinth with the three machines evaluated in this study did not immediately (i.e., within six months) produce weed free areas of open water in habitats typical of those found in the Sacramento/San Joaquin Delta.