J'P' Cuda

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Biological Control of WeedsBasic Principles and
Prospects for Hydrilla

• J.P. Cuda
• UF/IFAS
• Entomology Nematology Department
• Gainesville, FL 32611-0620

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Topics

• Biological Control Primer
• Hydrilla Example
• Questions? Comments?

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Topics

• Biological Control Primer
• Hydrilla Example
• Questions? Comments?

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TACTICS OF INvasive PlanT MANAGEMENT
PREVENTION
BIOLOGICAL
CULTURAL
CHEMICAL
PHYSICAL
IMPORTATION
AUGMENTATION
CONSERVATION
INORGANIC
ORGANIC
NATURAL
SYNTHESIZED
NATURAL
SYNTHESIZED
FORTUITOUS
Relative Degree of Sustainability
PERMANENT
TEMPORARY
Credit N. Leppla UF/IFAS
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What is Biological Control ?

• Planned Use of Undomesticated Organisms to Reduce
  the Vigor, Reproductive Capacity, or Density of
  Weeds (DeLoach 1997).
• Four Categories
• Augmentation (Arthropods, Pathogens, Grass Carp)
• Conservation (Arthropods, Habitat Manipulation)
• Importation or Classical (Arthropods, Pathogens)
• Fortuitous (Arthropods, Pathogens)

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Classical BioControl

• Introduction of Host Specific Natural Enemies
  from the Weeds Native Range to Permanently
  Suppress Populations of the Target Weed in its
  Adventive1 Range
• 1Arrived into a specified geographical region
  from elsewhere by ANY means.

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Conceptual Basis for Classical Biological Control

• Native Host Specific Enemies Strongly Control the
  Abundance and/or Distribution of Native Plants
• Escape from Host Specific Enemies is a Key
  Contributor to Exotic Plant Success
• Enemy Escape Benefits Exotics Because They Gain a
  Competitive Advantage Over Native Plants as a
  Result of Being Liberated from Their Pests

Williams (1954)
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Objective of Classical BioControl

• Release Host-Specific Natural Enemies Capable of
  Suppressing Maintaining the Weeds Density at
  ACCEPTABLE Levels
• Biological Control is NOT Eradication

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How Does BioControl Work ?

• Weed establishes equilibrium density (ED) above
  economic injury level (EIL)
• Natural enemy lowers ED maintains it
  below EIL
• ED - Long term mean density
• EIL Lowest density causing economic or
  ecological damage

Weed
Natural Enemy
ED
EIL
NUMBER
ED
TIME
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Defining BioControl Success(in Operational Terms)

• Complete- No other control
• methods are needed
• Substantial- Other methods needed but at
  reduced level
• Negligible- Other methods are
• required
• (Hoffmann 1998)

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BioControl of Alligatorweed Florida, ca. 1960s
Leaf Beetle Adult
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BioControl of Waterhyacinth Florida, ca.
1970s
Neochetina weevils
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BioControl of Hydrilla Florida, ca. 1980s
HYDRELLIA FLY LARVA
GRASS CARP
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Advantages of BioControl

• Minimal Impact on Non-targets
• Environmentally Friendly
• Classical Biocontrol is Permanent
• Suitable for Weeds of Natural Areas
• Minimal Disturbance

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Disadvantages of BioControl

• Control is Not Immediate (510 years)
• Little Interest in Commercialization
• Unpredictable
• Some Natural Enemies Fail to Establish
• Some Natural Enemies are Ineffective

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Costs/Benefits of BioControl
Release of Bioagent
Benefits ()
Time
Maintenance Monitoring
Costs (-)
Research Development
(after Mentz 1987)
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BioControl Pipeline
Credit USDA, ARS
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New Quarantine Facilities
USDA-ARS Laboratory, Ft. Lauderdale
UF/DACS Laboratory, Ft. Pierce
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Topics

• Biological Control Primer
• Hydrilla Example
• Questions? Comments?

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Surveys for New Natural Enemies of Hydrilla in
East Africa Preliminary Results

• J.P. Cuda1, W.A. Overholt1, R.S. Copeland ,
  E. Nkubaye, B. Nzigidahera, J.A.
  Ogwang, and F.M. Wanda

1Entomology Nematology DepartmentUniversity of
Florida, Gainesville and Ft. Pierce jcuda_at_ufl.edu
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Hydrilla verticillata (L.f.) Royle

• Rooted submersed aquatic plant
• Tropical and subtropical distribution
• Native range- Africa, Asia, Australia
• Monotypic stands
• Displace native spp.
• Reduce biodiversity
• Dense surface mats
• Impede navigation
• Interfere with flood
• control

http//www.dep.state.fl.us/lands/invaspec/index.ht
m
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Hydrilla Infestations Affect

• Water front homeowners
• Recreational anglers boaters
• Eco-tourists
• Sport divers
• Hydrologists
• Aquatic plant managers

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Hydrilla Control Costs

• Since 2000, Florida DEP spent between 13-18
  million to control hydrilla

http//www.dep.state.fl.us/lands/invaspec/2ndlevpg
s/pdfs/Aquatic202003-04.pdf
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Hydrilla in Florida

• Chronology of events
• 1958- Introduced into Tampa, Florida
• 1968- Correctly IDd herbicides ineffective
• 1970s- Rapid spread throughout Florida
• 1972- Release of grass carp
• 1980- Use of fluridone (Sonar) herbicide
• 1987- First BioControl agent established
• 2000- Fluridone resistance confirmed
• 2005- Renewed interest in BioControl

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Biological Control - History

• Hydrilla invasion stimulated early interest in
  BioControl
• Adventive moth, Parapoynx diminutalis, appeared
  in FL in 1970s, but minimal impact
• Several insects from Asia introduced into Florida
  in 1980s
• The fly, Hydrellia pakistanae, established, but
  had little effect
• Midge, Cricotopus lebetis, providing some control
  of hydrilla in Crystal River since1990s.
• Unknown whether native or exotic

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Life Cycle of Cricotopus lebetis
Eggs
Larva
Pupa
Adult
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Larva and Associated Tip Damage
Mature Larva
Normal
Damaged
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Hydrilla Midge Impact
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Grass Carp

• Sterile (triploid) grass carp can be used to
  manage hydrilla.
• They are not selective feeders.
• Can only be used in closed water bodies

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Hydrilla Native Distribution
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African Hydrilla Distribution(based on herbaria
and literature records)
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Objectives

• Establish Collaborative Linkages with Research
  Institutions in East Africa
• Conduct Preliminary Surveys for Hydrilla and its
  Natural Enemies

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Hydrilla Survey, E. Africa, Sep 2005

• Three Countries Visited
• Kenya
• Burundi
• Uganda

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Institutions Visited

• Kenya
• ICIPE, Nairobi
• ICIPE, Mbita Point
• Kenyatta University
• Burundi
• INECN
• ISABU
• Burundi University
• Uganda
• NARO
• Makerere University

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Collecting SamplesLake Tanganyika, Burundi, Sep
2005
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Processing SamplesBujumbura, Burundi, Sep 2005
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Collecting SamplesLakes Bisina and Kyoga,
Uganda, Dec 2005
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Processing SamplesJinja, Uganda, Dec 2005
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New Hydrilla Records, UgandaSince September 2005
Lake Bisina
Lake Opeta
Lake Kyoga
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Hydrilla Locations, Sep 2005
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Water Quality ParametersLakes Bisina and Kyoga,
Uganda, Dec 2005
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Natural Enemies Lake Tanganyika, Burundi, Sep
2005
Bagous sp. (coenosus sp. grp.)
Cricotopus sp. Polypedilum sp.
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Summary

• Hydrilla- one of Floridas most troublesome
  aquatic weeds
• Herbicide resistant populations discovered in
  several water bodies
• Based on molecular studies, some African material
  similar to Florida hydrilla

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Summary (contd)

• Hydrilla not recorded as a problem aquatic plant
  in Africa insect herbivores could be the reason
• Reared two potentially interesting insects from
  Hydrilla in Lake Tanganyika
• Collaborators are continuing the work
• BioControl may offer a possible solution

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Future Research

• Evaluate ability of East African insects to
  develop entirely on submersed hydrilla
• Conduct biological and preliminary host range
  studies of candidate natural enemies for
  importation into US quarantine
• Seek support for investigating host range and
  potential geographic distribution of naturalized
  midge Cricotopus lebetis

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Thank You
Jim Cuda
Bill Overholt
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Topics

• Biological Control Primer
• Hydrilla Example
• Questions? Comments?