Salvinia molesta Infestation in the Lower Colorado River

“Salvinia molesta. Infestation in the Lower Colorado River. ” Presents: Oscar H. Torres U. University of Arizona Department of Soil, Water and Environmental Science. Aquatic Plants Course, SWES 525.

Antecedents. n n n Mitchell (Giant salvinia). Brazilian native, free floating aquatic fern. Reproduces by vegetative fragmentation.

History n 1999 USFWS discovered S. molesta within the Cibola National Wildlife Refuge. n Other reports as South as Yuma, AZ. n Origin: Irrigation outfall drain (Palo Verde Irrigation District, [PVID]).

Adverse effects Blocks water system’s intakes and outlets. n Ecology & Economy: Limiting free water space (Recreation). Usurping in situ vegetation. Increasing anoxic conditions (Fishery). n

Infested Sites

Lower Colorado River Giant Salvinia Task Force Bureau of Reclamation. n Bureau of Land Management. n Fish and Wildlife Service. n Department of Agriculture. n PVID. n Other local, State, and Mexican Agencies. n

Objective n Eradicating or controlling S. molesta along PVID and Lower Colorado River (LCR). Integral Action Plan Physical control. Chemical spray applications. Biological control. Public information.

Physical Removal (PR). n n -Nets. -Excavation. -Booms. -Skimmer.

PR n Advantages: n Non polluting. n Disadvantages: n Expensive and effort consuming. n Complete removal was not usually achieved (native flora).

Chemical applications (CA). Chelated Copper 10% to 15% Solution. (Clearigate, Komeem). n Diquat-Glyphosate Mixture 15% diquat-5% glyphosate Solution, and Surfactant. n Diquat alone. n

CA. Fluridone. n Diquat dibromide and Surfactant. n Glyphosate and Surfactant. n

CA

CA Advantages n Effective on eradicating plants. n

CA (Disadvantages) Could copper levels. n Glyphosate and diquat have { } use in waters with sediments. n Copper based, { } where fauna resides, & where =CO 3> 50 ppm. n Non substrate specific. n Polluting. n Expensive & Effort consuming. n

Biological Control (BC). n n n Cyrtobagous salviniae weevils. 2001 USDA approved tests on biocontrol. 2003 USDA approved release at LCR.

BC. From 2003 to 2005 weevils controlled salvinia population where applied. n Weevils need + time. n + investigation to conclude if weevils are successful in long spans. n

BC n Advantages Species specific. n + Effective in stagnant waters. n Inexpensive. n

BC Disadvantages n - Ineffective during winter (~5° C). n - Ineffective on waters. n

Public Education and Outreach

Throughout 2006 August: Biocontrol monitoring continues along LCR: 3000 weevils/m 2. n October: Diquat & glyphosate application: @ Estes & Browns drain (salvinia present). n Spraying as salvinia disappeared. n

Conclusions & propositions n The integrated approach solution has reached the results.

Conclusions & propositions n n BC: research on larvae. 3 years of continual evaluation. Reclamation procedures: successful in stagnant waters

Conclusions and proposals Perhaps curbed salvinia: natural conditions limited nutrients turbulence temperature n Removal of 90 -95% @ PVID. n Removal on river: total (natural conditions? ) n