Research problem being addressed and background:
Over the last several years, increasing levels of the two noxious aquatic plants, hydrilla and waterhyacinth, have become a serious problem in the Lower Rio Grande Valley (LRGV). In 1998, the weed infestations were cited as the worst on record for both the Rio Grande and for most, if not all, of the 28 irrigation districts in the LRGV. These plants have restricted water delivery and led to inaccurate water accounting and an overall breakdown of system maintenance.
Infestations of these two weed species coupled with a prolonged drought in the area also contributed to observed water losses. The Texas Water Master and the LRGV District Managers Association both reported that infestations of waterhyacinth and hydrilla were main contributors to the excessive water loss. Water losses within the LRGV occurred through increased plant evapotranspiration, the water needed to surge to break through weed dams (which is subsequently lost as tail water), and lost to seepage as a result of water backups where weeds blocked canals.
| Sampling waterhyacinth during surveys to measure numbers of biological control insects. |  |
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- To develop an Integrated Pest Management (IPM) Plan to combine pest control practices with the goals of irrigation system operation and municipal water delivery and profitability, consistent with laws and regulations of the State of Texas. This plan also satisfies a cooperative agreement between the Bureau of Reclamation and ten irrigation districts in the LRGV.
- To ascertain current status of naturalized insects. We will use state of the art insect monitoring techniques for characterizing levels of biological control insects of waterhyacinth and hydrilla at several LRGV sites. A summary report will serve as background data for insect demonstration sites in the next objective.
- To adapt procedures to use these biological control methods at specific LRGV sites by augmenting existing populations of biological control insects for hydrilla and waterhyacinth.
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Overall Outcome or Conclusions:
The Science and Technology program addressed all three objectives:
- Wrote an IPM Plan, which is currently undergoing peer review by the cooperating agencies. A final version will be completed in the next two months.
- Monitored insect populations at numerous sites in the LRGV and wrote a summary report.
- Made initial releases of waterhyacinth insects at one site. Additional release sites will be established next growing season.
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Partners who participated in the project:
- Bureau of Reclamation
- Great Plains Region
- Oklahoma-Texas Area Office
- Office of Policy
- Ten Irrigation Districts in the LRGV (cooperative agreement)
- Texas Parks and Wildlife Texas
- Natural Resources Conservation Commission
- International Boundary and Water Commission
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Publications and/or Other Deliverables which have been provided during this fiscal year:
Grodowitz, Michael J., Jan E. Freeman, Harvey Jones, Lavon Jeffers, Carlos Lopez, and Fred Nibling, 2000, Status of Waterhyacinth/Hydrilla Infestations and Associated Biological Control Agents in Lower Rio Grande Valley Cooperating Irrigation Districts, U.S. Army Corps of Engineers Environmental Laboratory ERDC/EL SR-00-11.
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