Biological Control of Giant Salvinia

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Biological Control of Giant Salvinia (salvinia
molesta) on Lower Colorado River
Earl Andress (APHIS, USDA) Sangho Choi (Univ. of
Arizona)
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Introduction

• Cyrtobagous salviniae, a salvinia weevil
  originally collected from Brazil, has been
  successfully used in biological control programs
  throughout the world to control the exotic
  aquatic fern, Salvinia molesta, Giant Salvinia
  (GS).

• For the past 2 years, a strain of C. salviniae
  collected from Australia has been undergoing
  evaluation in the United States, with the goal of
  developing a GS biological control program and
  subsequently transferring this technology to
  cooperators in salvinia-infested states.

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Biological Control of Giant Salvina

• Phase 1
• The agents have been studied and mass-produced in
  the laboratory at the Plant Protection and
  Quarantine (PPQ), Center for Plant Health Science
  and Technology (CPHST) Plant Protection Lab (PPL)
  in Edinburg, TX.
• Insects have been field-released since October
  2001 in Southeast Texas.
• - Post-release evaluations to determine insect
  establishment, population increase and impact on
  non-target native species.

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Biological Control of Giant Salvina

• Phase 2
• - Establish four (4) field release sites
  (insectaries)
• Complete protocol covering site identification,
  insect release, and post-release sampling

Phase 3 - Managing the field insectaries and
continuation of the GS biological control program
- Collecting C. salviniae from the field
insectaries for redistribution and establishment
in other locations.
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Ecology of Biological Control Agent
Cyrtobagous salviniae (Coleoptera)

• 1. Description
•  
• Adults are typically black or brown ranging in
  length from 1.5 to 2.0 mm.
• Adults typically reside on surface or beneath
  the leaves or fronds of S. molesta.

• 2. Reproduction
• Eggs are laid singly in cavities formed by
  females feeding activity.
• Hatching occurs in approximately 10 days.
• The pre-pupal and pupal periods last about 2
  weeks.
• Total larval development requires 3 to 4 weeks.  

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Ecology of Biological Control Agent

• 3. Feeding Damage
•  
• Adults feed on the leaves leaving small holes
  (bullet hole)
• Larvae feed within the roots, rhizomes, and leaf
  buds and can be devastating (more effective
  control than adult).

4. Plant Effects - Initial establishment is
dependent on the nitrogen content of the plants.
- During the early damaging phase plants turn
brown and subsequently begin to sink.
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Site I about 3 km below Coco Palm
Site II About 3 km above Walters Camp
Site III About 2 km above Imperial Dam (Squaw
Lake)
Site IV About 3 km above Morales Dam
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Site Description
Site I - About 3 km below Coco Palm - Relatively
narrow, deep, and fast flowing
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Site Description
Site II - About 3 km above Walters Camp -
Relatively wide, shallow, and slow moving (G.S
attached to other aquatic plants)
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Site Description
Site III - About 2 km above Imperial Dam (Squaw
Lake) - Relatively wide, and high potential for
human disruption
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Site Description
Site IV - About 3 km above Morales Dam -
Relatively wide, shallow, and slow moving (G.S
attached to other aquatic plants)
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Result
Physico-chemical data Temperature, Dissolved
Oxygen and pH
site I Coco Palm, site II Walters Camp, site
III Imperial Dam, site IV Morales Dam
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Result
Physico-chemical data Nutrients ( mg/L)
site I Coco Palm, site II Walters Camp, site
III Imperial Dam, site IV Morales Dam
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Site II 7/17/03
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Summary

• The ultimate goal of this project is to reduce
  the environmental, social, and economic impacts
  of S. molesta. 
• We need more time to draw conclusions about the
  efficiency of this biological agent in the Lower
  Colorado River system.
• We hope C. salviniae will survive winter of 2003
  -2004.
• The chances of success are good because
  biological control agents that have worked
  previously in similar climates have a higher
  probability of success.

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Questions?