Mechanisms for the Effective Biological Control of the Invasive Water Hyacinth, Eichhornia crassipes, in the Sacramento-San Joaquin River Delta, California

Start/End: April, 2016 to April, 2018

The invasive species water hyacinth, Eichhornia crassipes, grows abundantly in the Delta and causes serious ecological and economic harm.  To date, application of herbicides and mechanical removal/shredding have been costly and implementation has been difficult due to concerns of native endangered species. Although the classical biological control agent, Neochetina bruchi, results in damage to water hyacinth, current control outcomes in the Delta have not reached the desirable levels observed in other regions where classical biological control has been implemented.

This project will provide information to improve the management of water hyacinth by identifying factors that reduce the effectiveness of the herbivorous weevil N. bruchi. Specifically, it will investigate the effects of seasonal temperature variations, pathogens, genetic diversity, potential herbicide interactions, and the availability of a winter refuge on Delta populations of N. bruchi at 16 sites. Results from this study can be utilized to achieve effective control of water hyacinth and contribute to the control of other aquatic invasive weeds in the Delta, such as the Brazilian waterweed, Egeria densa.