Biological Control of Giant Salvinia ( salvinia molesta ) on Lower Colorado River

1. Biological Control of Giant Salvinia (salvinia molesta) on Lower Colorado River SANGHO CHOI (Univ. of Arizona)

2. Outline • Introduction • Ecology and problems of Giant Salvinia (Salvinia Molesta) • Control and Management • 4. Biological Control of Giant Salvinia • Conclusion and Summary • 6. Further study

3. Introduction • Aquatic macrophyte is one of the most important primary producers in aquatic ecosystem. • Excessive blooms may cause serious problems to the other biota and human • Giant Salvinia (native to Brazil) is dangerous aquatic weed

4. Ecology of Giant Salvinia (Salvinia Molesta) 1. Taxonomy : Salvinia Molesta 2. Identification - Free floating aquatic fern - Oblong floating leaves, ½ to 1 ½ inches long. - As plants mature aggregate into mats, leaves fold and compress into upright chains

6. Ecology of Giant Salvinia 4. Reproduction - Vegetative reproduction by fragmentation (Michell and Gopal 1991) - It can double in area every 2 ½ to 10 days 5. Habitat - Stable waters ; lakes and ponds, oxbows, ditches, rice fields, slow flowing streams and rivers.

7. Distribution of Giant Salvinia

8. Problems caused by Giant salvinia 1. Reducing Oxygen Content in water 2. Reducing native plant composition 3. Degrading water quality for fish and other organisms 4. Impeding boating, fishing, and swimming 5. Clogging water intakes for irrigation and electrical generation

9. Control and Management 1. No Action – no cost 2. Physical control - Hand Removal - Mechanical Removal 3. Chemical Control - Herbicides application 4. Biological Control - One of the most effective control technologies

10. Control and Management • The best way of weed control and management could be prevention • - Prevent the spread of Salvinia into other water system • 2. The Lower Colorado River • - Integrated management (combined method with physical, chemical and biological method) • - Work in cooperation with Mexico to limit the spread of Salvinia across the border and into Mexico

11. History of G.S. Biological Control 1. Cyrtobagous salviniae, a salvinia weevil originally collected from Brazil, has been successfully throughout the world to control the Giant Salvinia. 2. For the past 3 years(2001 -2003), a strain of C. salviniae (from Australia) has been undergoing evaluation in the United States.

12. Biological Control of Giant Salvina • Phase 1 • Mass-reproduction of biological agent at the Plant Protection and Quarantine (PPQ) and Plant Protection Lab (PPL) in Edinburg, TX. • Post-release evaluations to determine ; insect establishment, population increase and impact on non-target native species

13. Biological Control of Giant Salvina • Phase 2 • - Establish four (5) field release sites (insectary) • Site identification, insect release, and post-release sampling • Phase 3 • - Managing the field insectaries • - Collecting C. salviniae from the field insectaries for • redistribution and establishment in other locations.

14. Ecology of Biological Control Agent Cyrtobagous salviniae (Coleoptera) • 1. Description • Black or dark brown and length from 1.5 to 2.0 mm. • Adults typically reside on surface or beneath the leaves • 2. Reproduction • Eggs are laid singly in cavities. • Hatching (in 10 days). • The pre-pupal and pupal periods (2 weeks). • Total larval development requires 3 to 4 weeks.  

15. Ecology of Biological Control Agent • 3. Feeding Damage • Adults feed on the leaves (bullet hole). • Larvae feed within the roots, rhizomes, and leaf buds (more effective control than adult). • 4. Plant Effects • - Initial establishment is dependent on the nitrogen content. • - Plants turn brown and subsequently begin to sink.

17. Materials and methods 1. 6 release sites (500-700 adults of insects on each) 2. Biological agent analysis : 5 samples for each site with 20cm diameter food strainer : Identify other living organisms inside of plants : Counting numbers of insects (egg, pupae, larvae, and adults)

18. Site I : about 3 km below Coco Palm Site II : About 3 km above Walter’s Camp Site III : About 2 km above Imperial Dam (Squaw Lake) Site IV About 3 km above Morales Dam

19. Site Description • Site I • - About 3 km below Coco Palm • Relatively narrow, deep, and fast flowing • Site II • - About 3 km above Walter’s Camp • - Relatively wide, shallow, and slow moving (G.S attached to other aquatic plants)

20. Site Description • Site III • - About 2 km above Imperial Dam (Squaw Lake) • Relatively wide, and high potential for human disruption • Site IV • - About 3 km above Morales Dam • - Relatively wide, shallow, and slow moving

21. I II III IV

22. Physico-chemical data (n = 24) site I : Coco Palm, site II : Walter’s Camp, site III : Imperial Dam, site IV : Morales Dam Result

23. Site I 7/17/03 In 2 week In a month

24. Site IV 8/21/03 In 2 weeks In a month

25. Summary • The ultimate goal of this project is to reduce the environmental, social, and economic impacts of S. molesta.  • 2. We need more time to draw conclusions about the efficiency of this biological agent in the Lower Colorado River system. • 3. We hope will successful over-winter of C. salviniae in the river • 4. The chances of success are good because biological control • agents that have worked previously in similar environments.

26. Further Study • Low temp. resistance test on biological agent   • : whether they can successfully over-winter in the river • Additional release on the river • : both AZ and CA sides • 3. Long-term monitoring 

27. Acknowledgement • Dr. Kevin Fitzsimmons • Mr. Earl Andress (APHIS, USDA, CA) • Lower Colorado River Salvinia Task Force

28. Questions?