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United States Department of Agriculture

Agricultural Research Service

Title: Seasonal Growth of Water Hyacinth in the Sacramento/san Joaquin Delta, California: Implications for Management

Authors
item SPENCER, DAVID
item Ksander, Gregory

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2005
Publication Date: January 15, 2005
Citation: Spencer, D.F., Ksander, G.G. 2005. Seasonal growth of water hyacinth in the Sacramento/San Joaquin Delta, California: implications for management. Journal of Aquatic Plant Management 43: 91-94.

Interpretive Summary: Water hyacinth is a serious problem in the Sacramento Delta, CA. Little information on its growth in this ecosystem exists. Our objectives were to measure its seasonal growth to aid the timing of management techniques and to elucidate possible limits for bio-control in the Delta. Plants were sampled at 2 to 3 week intervals from November, 1995 to July, 1997. We measured plant dry weight, height, number of living and dead leaves, and the presence of flowers. Height and dry weight increased from less than 0.1 m in winter and early spring to more than 0.8 m in late summer and from 10 g to 85 g, respectively. New leaves appeared in March and leaf width increased through September. Maximum growth occurred later than reported for plants in southern states. An equation relating growth to accumulated degree-days and was used in conjunction with a 10-year data set of air temperature to predict that smaller plants (< 20% of maximum size) would be most often present between May 10 and June 30. Published results indicate that this stage is most susceptible to herbicide treatments. Accumulated degree-days for growth of two water hyacinth weevils indicated that two generations would be produced. Due to high air temperatures (> 35 C) predicted weevil reproduction ceased prior to water hyacinth attaining maximum growth.

Technical Abstract: Water hyacinth (Eichhornia crassipes) is a serious problem in the Sacramento Delta, CA. Little information on its growth in this ecosystem exists. Our objectives were to measure its seasonal growth to aid the timing of management techniques and to elucidate possible limits for bio-control in the Delta. Plants were sampled at 2 to 3 week intervals from November, 1995 to July, 1997. We measured dry weight, height, number of living and dead leaves, and the presence of flowers. Height and dry weight increased from less than 0.1 m in winter and early spring to more than 0.8 m in late summer and from 10 g to 85 g, respectively. New leaves appeared in March and lamina width increased through September. Maximum growth occurred later than reported for water hyacinth in southern states. An equation relating growth to accumulated degree-days and was used in conjunction with a 10-year data set of air temperature to predict that smaller plants (< 20% of maximum size) would be most often present between May 10 and June 30. Published results indicate that this is stage most susceptible to herbicide treatments. Accumulated degree-days for growth of two water hyacinth weevils indicated that two generations would be produced. Due to high air temperatures (> 35 C) predicted weevil reproduction ceased prior to water hyacinth attaining maximum growth.

Last Modified: 9/29/2014
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